PeristalticCrawler-FinalReport-Spring2010

PeristalticCrawler-FinalReport-Spring2010 - EML 4905 Senior...

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Unformatted text preview: EML 4905 Senior Design Project A SENIOR DESIGN PROJECT PREPARED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING Peristaltic Crawler for the Removal of Radioactive Plugs 100% Report Lee Brady Jose Matos Brian Posse Advisor: Professor Sabri Tosunoglu April 5, 2010 This report is written in partial fulfillment of the requirements in EML 4905. The contents represent the opinion of the authors and not the Department of Mechanical and Materials Engineering. Ethics Statement and Signatures The work submitted in this project is solely prepared by a team consisting of Lee Brady, Jose Matos, and Brian Posse and it is original. Excerpts from others work have been clearly identified, their work acknowledged within the text and listed in the list of references. All of the engineering drawings, computer programs, formulations, design work, prototype development and testing reported in this document are also original and prepared by the same team of students. Lee Brady Jose Matos Brian Posse Team Leader Team Member Team Member Dr. Sabri Tosunoglu Faculty Advisor i Table of Contents Abstract .................................................................................................................................................. 1 1. Introduction ........................................................................................................................................ 2 1.1 Problem Statement ........................................................................................................................ 2 1.2 Motivation ..................................................................................................................................... 3 1.3 Literature Survey ........................................................................................................................... 5 1.3.1 Industries use for Pipe Crawlers .............................................................................................. 5 1.3.2 Pipe Crawler Mounted Devices................................................................................................ 6 1.3.3 Pipe Crawler Designs ............................................................................................................... 7 1.3.4 Previous Unclogging Technologies at ARC ............................................................................. 11 1.3.5 Simulating Plugs .................................................................................................................... 14 1.3.6 Radiation Effects ................................................................................................................... 16 1.3.7 Effects of Radiation on Passive Materials............................................................................... 17 1.3.8 Radiation Hardening ............................................................................................................. 21 1.4 Discussion .................................................................................................................................... 22 2. Project Formulation ........................................................................................................................... 23 2.1 Overview ..................................................................................................................................... 23 2.2 Project Objectives ........................................................................................................................ 23 2.3 Design Specifications (Final Crawler) ............................................................................................ 24 2.3.1 The crawler ........................................................................................................................... 24 2.3.2 The Camera ........................................................................................................................... 30 2.3.3 Basic Principles of Locomotion .............................................................................................. 32 2.3.4 Bellow/Annular Actuator Design ........................................................................................... 34 2.3.5 Pneumatic System ................................................................................................................. 36 2.3.6 Hydraulic System................................................................................................................... 38 2.3.7 Failure Modes ....................................................................................................................... 39 2.4 Constraints and Other Considerations .......................................................................................... 41 2.5 Discussion .................................................................................................................................... 41 3. Design Alternatives ............................................................................................................................ 43 3.1 Design Alternate 1 ....................................................................................................................... 43 3.2 Design Alternate 2 ....................................................................................................................... 44 ii 3.3 Design Alternate 3 ....................................................................................................................... 45 3.4 Feasibility Assessment ................................................................................................................. 46 3.5 Proposed Design .......................................................................................................................... 49 3.6 Discussion .................................................................................................................................... 50 4. Project Management ......................................................................................................................... 51 4.1 Breakdown of Work into Specific Tasks ........................................................................................ 51 4.2 Organization of Work and Timeline .............................................................................................. 52 4.3 Breakdown of Responsibilities among Team Members................................................................. 53 4.4 Number of Hours Spent on Project ............................................................................................... 53 5. Engineering Design and Analysis ........................................................................................................ 54 5.1 Kinematic Analysis ....................................................................................................................... 54 5.2 Finite Element Analysis ................................................................................................................ 55 5.3 Force Analysis .............................................................................................................................. 61 5.3.1 Anchoring Force of the Inner Tubes ................................................................................... 61 5.4 Stress Analysis ............................................................................................................................. 64 5.4.1 Stress on Inner Tubes ............................................................................................................ 64 5.4.2 Stress Analysis on Tool Support ............................................................................................. 65 5.5 Deflection Analysis....................................................................................................................... 70 5.6 Material Considerations ............................................................................................................... 72 5.6.1 Crawler Materials.................................................................................................................. 72 5.6.2 Camera Selection .................................................................................................................. 75 5.7 Cost Analysis ................................................................................................................................ 76 5.7.1 Material Cost ........................................................................................................................ 76 5.7.2 Labor Cost ............................................................................................................................. 77 6. Prototype Construction ..................................................................................................................... 79 6.1 Description of Prototype .............................................................................................................. 79 6.1.1 Prototype System Description ............................................................................................... 82 6.2 Prototype Design ......................................................................................................................... 84 6.3 Parts List ...................................................................................................................................... 87 6.4 Construction ................................................................................................................................ 88 6.5 Prototype Cost Analysis................................................................................................................ 91 7. Testing and Evaluations ..................................................................................................................... 92 ii 7.1 Preliminary Testing ...................................................................................................................... 92 7.1.1 Preliminary Test Description ................................................................................................. 92 7.2 Preliminary Test Results ............................................................................................................... 93 7.2.1 Results: Bellow Material Test: ............................................................................................... 93 7.2.2 Results: Double Bellow Test: ................................................................................................. 96 7.2.3 Results: Design Feasibility Test ............................................................................................ 101 7.3 Design of Experiments Description of Experiments for Final Prototype .................................... 104 7.4 Test Results and Data ................................................................................................................. 106 7.4.1 Pulling Force ....................................................................................................................... 106 7.4.2 Vertical Crawling ................................................................................................................. 110 7.4.3 The Crawler s Speed ............................................................................................................ 111 7.4.4 Unplugging Ability ............................................................................................................... 113 7.5 Evaluation of Experimental Results ............................................................................................ 115 7.5.1 Pulling Force ....................................................................................................................... 115 7.5.2 Crawler Speed ..................................................................................................................... 116 7.5.3 Unplugging Ability ............................................................................................................... 117 7.6 Improvement of the Design ....................................................................................................... 118 7.7 Discussion .................................................................................................................................. 118 8. Design Considerations ..................................................................................................................... 119 8.1 Assembly and Disassembly......................................................................................................... 119 8.2 Maintenance of the System ....................................................................................................... 119 8.3 Environmental Impact ................................................................................................................ 119 8.4 Risk Assessment ......................................................................................................................... 120 9. Conclusion ....................................................................................................................................... 121 9.1 Conclusion and Discussion ......................................................................................................... 121 9.2 Commercialization Prospects of the Product .............................................................................. 122 9.3 Future Work .............................................................................................................................. 122 9. References ...................................................................................................................................... 125 10. Appendices .................................................................................................................................... 129 Appendix A. Detailed Engineering Drawings of Final Crawler Bodies .................................................... 129 Front Rim (Final) .............................................................................................................................. 129 Front Rim Side View..................................................................................................................... 129 ii Front Rim Front View ................................................................................................................... 130 Front Rim Rear View .................................................................................................................... 131 Front Rim Detailed View .............................................................................................................. 132 Rear Rim (Final) ............................................................................................................................... 133 Rear Rim Side View ...................................................................................................................... 133 Rear Rim Rear View ..................................................................................................................... 134 Rear Rim Front View .................................................................................................................... 135 Rear Rim Detailed View ............................................................................................................... 136 Appendix B. Detailed Engineering Drawings of Prototype Crawler Bodies ............................................ 137 Front Rim (Prototype) ...................................................................................................................... 137 Front Rim Side View..................................................................................................................... 137 Front Rim Front View ................................................................................................................... 138 Front Rim Rear View ................................................................................................................... 139 Front Rim Detailed View .............................................................................................................. 140 Rear Rim (Prototype) ....................................................................................................................... 141 Rear Rim Side View ...................................................................................................................... 141 Rear Rim Front View .................................................................................................................... 142 Rear Rim Rear View ..................................................................................................................... 143 Rear Rim Detailed View ............................................................................................................... 144 Appendix C: US Department of Energy Material Evaluation Charts [31] ............................................... 145 Appendix D: Raw Design Calculations .................................................................................................. 147 Appendix E: Catalogs ........................................................................................................................... 150 ii List of Figures Figure 1: The Columbia River [19] ............................................................................................................ 3 Figure 2: Rotary Design Robot [9] ............................................................................................................ 7 Figure 3: Angled Wheel Concept [9]......................................................................................................... 8 Figure 4: DSM Miniature Pipe Crawler [10] .............................................................................................. 8 Figure 5: Pneumatic Pipe Crawler [11] ..................................................................................................... 9 Figure 6: Pneumatic Pipe Crawler [12] ..................................................................................................... 9 Figure 7: Pipe Crawler Tractor with Forward Motion Wheel Direction [13] ............................................ 10 Figure 8: Pipe Crawler Tractor with Side-ways Motion Wheel Direction [13] .......................................... 10 Figure 9: Pipe View of Extendable Leg Crawler [14]................................................................................ 10 Figure 10: Side View of Extendable Leg Crawler [14] .............................................................................. 11 Figure 11: Final Rim vs. Prototype Rim ................................................................................................... 24 Figure 12: Bore and Ports of Final vs. Original Rim ................................................................................. 25 Figure 13: Multiple Output Ports ........................................................................................................... 25 Figure 14: Clamps to Secure Inner Tubes ............................................................................................... 27 Figure 15: Rear View of Final Crawler .................................................................................................... 28 Figure 16: Final Assembly of Crawler ..................................................................................................... 29 Figure 17: Waste Flow through Crawler ................................................................................................. 29 Figure 18: Micro Camera [27] ................................................................................................................ 30 Figure 19: Camera Location ................................................................................................................... 31 Figure 20: The Crawler s Locomotion (1st Prototype is featured) ........................................................... 32 Figure 21: Cross-Section of Bellow ......................................................................................................... 34 Figure 22: Example of an Edge Welded Bellow....................................................................................... 35 Figure 23: Cross-Section of Bellow Showing Air Lines ............................................................................. 35 Figure 24: Schematic of Pneumatic System ............................................................................................ 37 Figure 25: Schematic of Hydraulic System .............................................................................................. 38 Figure 26: Alternative Crawler 1 ............................................................................................................ 43 Figure 27: Alternative Crawler 2 ............................................................................................................ 44 Figure 28: Alternative Crawler 3 ............................................................................................................ 45 iii Figure 29: Gantt Chart ........................................................................................................................... 52 Figure 30: Basic finite element analysis (FEA) representation of pressurization sequence on a simplified model .................................................................................................................................................... 55 Figure 31: Straight Motion of the Crawler .............................................................................................. 59 Figure 32: Turning of the Crawler on an Elbow ...................................................................................... 59 Figure 33: Validation of Turning Ability with respect to Geometry ......................................................... 60 Figure 34: Maximum Pulling Force as a Function of the Balloon Pressure............................................... 61 Figure 35: Inner Tube Thickness for Anchor Test .................................................................................... 62 Figure 36: Pulling Force Test .................................................................................................................. 63 Figure 37: Inner Tube Stress .................................................................................................................. 64 Figure 38: Initial Tool Support, 50 lb load, 0.05 in. Mesh Size ................................................................. 66 Figure 39: Initial Tool Support 0.05 in. Mesh Size ................................................................................... 67 Figure 40: Final Tool Support, 350 lb Load, .05 in. Mesh Size.................................................................. 67 Figure 41: Final Tool Support 0.05 in. Mesh Size .................................................................................... 68 Figure 42: Von Mises Stress in Ansys (Exaggerated Deformation Scale).................................................. 69 Figure 43: Von Mises Stress in Solidworks (Exaggerated Deformation Scale) .......................................... 69 Figure 44: Initial Tool Support Displacement.......................................................................................... 70 Figure 45: Final Tool Support Displacement (True Scale) ........................................................................ 71 Figure 46: Ansys Displacement (Deformation Exaggerated Scale) .......................................................... 71 Figure 47: Radiation Dosage Required for 25% Damage ......................................................................... 73 Figure 48: Images of the CCD Camera in a Radioactive Environment [29] ............................................... 75 Figure 49: Nozzle Attachment ................................................................................................................ 79 Figure 50: (a) Crawler with Auger Installed, (b) Auger ............................................................................ 80 Figure 51: Cross Sectional View of the Crawler ...................................................................................... 81 Figure 52: System Configuration ............................................................................................................ 82 Figure 53: General Schematic of the Pressure Lines in the Pipeline ........................................................ 83 Figure 54: Rear Rim - Back Side .............................................................................................................. 84 Figure 55: Rear Rim - Front Side............................................................................................................. 85 Figure 56: Front Rim - Rear Side............................................................................................................. 85 Figure 57: SolidWorks Modeled Crawler Assembly ................................................................................ 86 iii Figure 58: Physical Crawler Assembly .................................................................................................... 86 Figure 59: Crawler Bodies Unassembled ................................................................................................ 88 Figure 60: Pneumatic Inputs .................................................................................................................. 89 Figure 61: a. Outer Bellow Over Inner b. Coiled Hose to Feed Front Rim ................................................ 90 Figure 62: Pressure Nozzle Affixed to Crawler ........................................................................................ 90 Figure 63: Contracted View of the Hard Plastic Bellow ........................................................................... 93 Figure 64: Expanded View of the Hard Plastic Bellow ............................................................................. 93 Figure 65: Defects on Hard Plastic Bellow .............................................................................................. 94 Figure 66: Neoprene Bellow Defect ....................................................................................................... 94 Figure 67: Expansion of the Thermo Plastic Bellow ................................................................................ 95 Figure 68: Contraction of the Thermo Plastic Bellow.............................................................................. 95 Figure 69: Contraction of the Clear PVC Bellow...................................................................................... 95 Figure 70: Expansion of the Clear PVC Bellow ........................................................................................ 96 Figure 71: Double Bellow Test Samples.................................................................................................. 96 Figure 72: Test Jig for the Double Bellow Test ........................................................................................ 97 Figure 73: Modified Air Passage for the Third Combination Test ............................................................ 97 Figure 74: Contraction of the First Bellow Configuration Test ................................................................ 98 Figure 75: Expansion of the First Combination of the Double Bellow Test .............................................. 98 Figure 76: Clearance Issue between the Bellows.................................................................................... 98 Figure 77: Contraction of the Second combination Bellow Test.............................................................. 99 Figure 78: Expansion of the Second Combination Bellow Test ................................................................ 99 Figure 79: The Clearance of the Second Combination Test ..................................................................... 99 Figure 80: Contraction of the Third Combination Bellow Test .............................................................. 100 Figure 81: Expansion of the Third Combination Bellow Test ................................................................. 100 Figure 82: Clearance of the Third Combination Bellows ....................................................................... 101 Figure 83: Solenoid Setup with Plumbing and Controls ........................................................................ 102 Figure 84: Expansion of the 1st Prototype ........................................................................................... 102 Figure 85: Contraction of the 1st Prototype ......................................................................................... 102 Figure 86: Inner Tube Decompression ................................................................................................. 103 Figure 87: Inflation of Inner Tube ........................................................................................................ 103 iii Figure 88: Calculating Force ................................................................................................................. 105 Figure 89: Pneumatic Lines Fastened to Hydraulic Line ........................................................................ 106 Figure 90: Area Created by Double-Bellow........................................................................................... 107 Figure 91: Pulling Force Test ................................................................................................................ 107 Figure 92: Spring Scale......................................................................................................................... 108 Figure 93: Vertical Crawling ................................................................................................................. 110 Figure 94: Straight Test Bed ................................................................................................................. 112 Figure 95: 90 Degree Test Bed ............................................................................................................. 112 Figure 96: Crawler Approaching Nozzle................................................................................................ 114 Figure 97: Plug Breaking Under Water Pressure................................................................................... 114 Figure 98: Plug Cleared Out ................................................................................................................. 115 Figure 99: Compressed Length of 9 Inches ........................................................................................... 116 Figure 100: Extended Length of 14 Inches ............................................................................................ 116 Figure 101: Crawler Housing ................................................................................................................ 120 Figure 102: Clearance of Future Crawler Idea ...................................................................................... 123 Figure 103: Conceptual Design of Future Crawler ................................................................................ 124 iii List of Tables Table 1: Photon tenth value thickness in cm for Al, Fe, Pb and concrete [25] ......................................... 16 Table 2: Radiation Damaged Thresholds on Metals [25] ......................................................................... 17 Table 3: Radiation Damage Thresholds on Ceramics [25] ....................................................................... 18 Table 4: Radiation Tolerance of Plastics [25] .......................................................................................... 19 Table 5: Radiation Damages on Coatings [25] ........................................................................................ 19 Table 6: Radiation Damages on Adhesives [25] ...................................................................................... 20 Table 7: Radiation Effects on Lubricants [25] ......................................................................................... 20 Table 8: Project Hours ........................................................................................................................... 53 Table 9: Ansys vs. SolidWorks Results .................................................................................................... 68 Table 10: Cost List of Final Major Components ...................................................................................... 76 Table 11: Labor Costs ............................................................................................................................ 77 Table 12: Parts List ................................................................................................................................ 87 Table 13: Prototype Cost Analysis .......................................................................................................... 91 Table 15: Pulling Forces ....................................................................................................................... 108 Table 16: Prototype Crawler Speed Assessment .................................................................................. 111 iv iv Abstract A self-propelled, pneumatic, peristaltic pipe crawler for unplugging clogged, radioactive waste transport lines and treatment plants at United States Department of Energy sites is proposed. As the name implies, the peristaltic pipe crawler will move forward by a series of contractions and expansions, in a worm-like motion, by inflating and deflating three major air cavities along the crawler s body. The crawler has a front and rear body, each body holds inner tubes that inflate and deflate according to the crawling motion. Supporting these two bodies is a bellow-like body. One bellow is inside the other creating a cavity where air can expand and contract the bellows. To advance the crawler, air is supplied in a sequential manner into the different air chambers of the crawler. The frontal body will hold an abrasion tool to remove blockages in pipes. The crawler will be able to move through 90 degree bends having a turning radius of 4.5 inches. Major design challenges exist not only due to the radioactive environment, but also due to sizing constraints that are involved in designing a crawler for a 3 inch diameter pipe. Proper sizing and pressure values are needed to ensure the crawler can negotiate 90 degree elbows. Further adding to the complexity of the crawler design, an abrasive tool must be affixed to the front of the crawler. The tool must not hinder the crawler s locomotion yet still be effective against removing plugs. Radioactive plugs can be simulated by using simulant plugs that possess similar physical and chemical properties yet remain non-hazardous for safe testing purposes. In order to understand the feasibility of such a crawler, engineering and design analyses will be studied. A prototype will be constructed and tested. 1|Page 1. Introduction 1.1 Problem Statement During World War II between the years of 1942 to 1946, the United States government led what was known as the Manhattan Project. In fear that Nazi Germany had been developing nuclear weaponry, the Manhattan Project s objective was to produce the first nuclear bomb. Since then an estimated 55 million gallons of highly radioactive waste used to form nuclear bombs have been stored in 149 single-shell tanks (SSTs) at the Hanford Site in Washington State [1]. The SSTs are made of a single layer of stainless steel and have stored the high level radioactive waste, composed of sludge, salts and liquids for decades. As of 2008, 68 of the SSTs have shown signs of leaks and the waste needs to be transported to the 28 double-shell tanks (DSTs) [1]. The United States Department of Energy s method for transporting the high level waste has been by way of underground pipelines having an inner diameter of approximately 3 inches. Once the radioactive waste is moved from the aging tanks it will later be transported to pretreatment and treatment facilities. The underground pipelines as well as the pipelines in the treatment facilities are susceptible to clogs while transporting the high level waste mixture of slurry and sludge. Radioactive waste transported in slurry-form can undergo physical, chemical, and changing flow conditions that cause blockages to occur in the pipelines. Currently the Department of Energy is behind schedule in the transfer of waste. The Department of Energy s deadline to empty the SSTs was 2018 but it has been extended to the year 2040 [2]. Clogged underground pipelines as well as clogs in the processing facilities retard the timeline of waste transfer even further, increasing costs and further threaten the environment. 2|Page 1.2 Motivation The Hanford Site s nuclear reactors were cooled by the vast amounts of water supplied by the Columbia River. The Columbia River stretches 1243 miles, from British Columbia, Canada to the border between Washington and Oregon, where it exits to the Pacific Ocean. The Hanford Site is illustrated in Figure 1. According to Hanford officials the radioactive material can reach the river in as little as three years, threatening human life and wildlife [7]. Figure 1: The Columbia River [19] 3|Page The leaks have already accounted for an estimated 270 billion gallons of contaminated soil and ground water in neighboring aquifers [3]. The crawler will provide the technology needed to remove clogs in transfer pipelines and/or treatment facilities which will shorten downtime, thus aiding in the effort to meet crucial deadlines. Previous studies held between the years 2000-2002, at Florida International University (FIU) included the testing and evaluation of several unplugging technologies. Based on the testing, two technologies were identified that could potentially withstand the rigors of operation in a radioactive environment and have the ability to handle sharp 90° elbows. The two technologies, NuVision Engineering s wave erosion technology and AIMM Technology s Hydrokinetic method, were evaluated again in 2007 and 2008 with the intention of understanding the underlying physics of the technologies and determine what limitations they have when operating within the safety constraints imposed by the sites. Results from these tests indicated that NuVision s technology offered promise but required additional phases of testing before it was mature enough for implementation at the sites. Results from the AIMM s testing indicated that the air remaining in the pipeline and a 300 psi maximum pressure limit significantly limited the capability of the technology. The previously tested unplugging technologies failed to achieve satisfying results as their unplugging capabilities drastically reduce as the distance to the plug increases. The crawler will solve this problem as it will crawl to the plug applying abrasive and other techniques to remove the plug. 4|Page 1.3 Literature Survey Robot pipe crawlers have been developed for various duties involved in the industries. A robot construction allows it to work in long lengths of pipes, including many bends, and inclined to vertical sections of piping. A robot can be made up of multiple types of driving unit configurations and a head module that can be fitted according to the job the robot has to perform. Pipe crawlers have been used in various industries to perform specific duties. 1.3.1 Industries use for Pipe Crawlers The areas that the pipe crawlers have been used range from large scale nuclear plants to the food industry, below are some of the industries that use pipe crawlers. · In nuclear power plants there are high safety concerns on the containment of the material being transported throughout the pipe, which entails that the pipes need to be inspected by pipe crawlers. · In conventional power plants robots are used to inspect for defects and faults in the pipes to keep the facilities going through their day by day bases. · Refineries are provided pipe crawlers to improve supply, transportation, processing and distribution of mineral oil; while still thinking about environmental protection. · Chemical plants use the robots to aid in the transport and storage of chemicals by the testing and inspections conducted to avoid the dangers involved in that industry. · Offshore rigs have a major concern in safety and environmental issue that require the inspection of pipe by the use of robots. 5|Page · In long distance city heating pipelines need to be inspected so that the energy and water losses could be minimized through the transportation of the heat from the source to the end user. · The food and drink industry has a high standard in hygiene, the use of inspection robots within the pipe with the appropriate tools ensure that the level of hygiene is appropriate. · Communal waste water pipe systems which are responsible for the collection and transportation of waste water use the robots to inspect the public sewage systems. · Gas pipelines use pipe crawlers for the inspection and maintenance of their pipeline network. 1.3.2 Pipe Crawler Mounted Devices Pipe crawling robots fitted for inspection use a wide array of devices mounted on the head and even throughout the body of the unit for the collection of data the machine is required to retrieve. Robots fitted with video cameras allow the user to visually inspect the conditions the robot encounters. Ultrasonic and eddy current capabilities which are used to check the condition of the pipes wall and thickness can be fitted on the robot. For corrosion and crack detection there are various types of lasers that can also be attached to the robot. The surface of a pipe can be corrected by the use of robots with special cutting tools attached to the head or body of the crawler. A grinding tool can be affixed to the robot for the removal of weld roots within the interior of pipe systems. This is important for certain industries due to the fact that it allows a clean and smooth surface for the flow of material and accurate testing. A milling robot can be used in situations where grooves needed to be grounded down and defects in the pipe can be removed. This allows nuclear power plants the ability to maintain many of their reactors. 6|Page 1.3.3 Pipe Crawler Designs There are a number of driving designs for the pipe crawling robot, below are a few patented designs: · As seen in · Figure 2 and Figure 3, the screw drive, rotary, design was built by a few Florida Atlantic University students for their Senior Report. The design has free-spinning wheels which are angled to provide the forward and reverse motion of the unit, while using a rotary motor to provide the drive of the robot. Figure 2: Rotary Design Robot [9] 7|Page Figure 3: Angled Wheel Concept [9] · Another rotary designed by Dynamic Structures & Materials, LLC (Figure 4) uses a miniature DC brushless motor and locomotion technique. It also uses wheels in a helical configuration, with spring-loaded wheels to keep in contact with the pipe walls. Figure 4: DSM Miniature Pipe Crawler [10] · A pneumatically-operated pipe crawler design, similar in concept to the current proposed design, is illustrated in Figure 5. This unit uses a series of rubber expansion chambers to propel the crawler down the pipe. 8|Page Figure 5: Pneumatic Pipe Crawler [11] · As shown in Figure 6, the extendable pipe crawler design is much simpler; it consists of front and back leg assembly connected by two air cylinders. It moves like an inchworm , the front and back leg assembly wheels engage and disengage simultaneously. Figure 6: Pneumatic Pipe Crawler [12] 9|Page · The pipe crawler tractor seen in Figure 7 and Figure 8, consist of a three wheel sectioned assembly. The first and last wheels contact the pipe wall opposite the middle wheel. The wheels also rotate to allow the unit to spin within the pipe, which uses a control system to allow this function Figure 7: Pipe Crawler Tractor with Forward Motion Wheel Direction [13] Figure 8: Pipe Crawler Tractor with Side-ways Motion Wheel Direction [13] · The pipe crawler with extendable legs is designed to have an inchworm motion, but instead of using wheels it has four legs around to grasp the cylinder walls in four radial sections. It can be seen in Figure 9 and Figure 10, this design uses air cylinders to allow the legs to walk the pipe. This is a pneumatic system with an electronically controlled manifold. There is also a rolling mechanism to reduce friction between the crawler and cylinder wall. Figure 9: Pipe View of Extendable Leg Crawler [14] 10 | P a g e Figure 10: Side View of Extendable Leg Crawler [14] 1.3.4 Previous Unclogging Technologies at ARC Using a crawler to unclog high level waste lines is only one of several techniques available. There have been several trials with other technologies that operate under various principles. Many designs involve the use of water pressure or pulsations and others use tubes or other solid objects that travel along the pipeline and are used to clear-out blockages. These methods have been met with some success, however none has been deemed ideal and it is believed that a crawler could be more efficient at serving this purpose. One of the other technologies tested is the so called Harben Jet which was created by Harben, Inc. The Harben Jet is a trailer that has a water tank and 500 ft of hose mounted to it. There is a nozzle placed on the end of the hose and there are different nozzles available so that the appropriate one may be selected for each task. The nozzles have several openings, including ones in the back which are used to drive the nozzle along the pipe. The overall idea is that the pressurized water coming out of the nozzle will forcefully clean out any clogs in the pipe. The water comes out at a pressure of up to 4000 psi and the system vibrates the hose in order to shake it around bends in the pipe. This technology may be deployed and then retracted within a short period of time and the cost is low. However, this technology uses a lot of water which is not recycled and it is not effective against certain types of clogs [18]. 11 | P a g e Carolina Equipment & Supply has a similar technology called the Aqua Miser. The device consists of a trailer with a water tank and a hose much like the Harben Jet. It also uses the same concept of a nozzle end which propels itself with backward facing openings. However, this device has 400 ft of hose and produces 40,000 psi, ten times the pressure output of the Harben Jet. Another difference is that it pumps lower volumes of water and so less is wasted. The Aqua Miser is low cost, can be deployed quickly, and may be considered a better alternative to using the Harben Jet. However, the device has no provision to vibrate the hose and so it is not as capable of maneuvering around elbows in the pipeline. After travelling 200 ft, the device does not have enough forward thrust to keep moving through elbows and becomes stuck after just two elbows in the pipe [18]. A company called The Atlantic Group developed a device that uses sound waves in order to unclog waste transfer pipes. The device produces up to a maximum frequency of 11,250 vibrations per minute. These sound waves will cause the clogs and the pipes to vibrate and as they will both vibrate at different rates, the clog will come loose from the pipe. A high pressure water pump is used to send water down the pipe at 2,100 ft/s, which serves to amplify the vibrations and to clear away the clog. This device has a large advantage over the others in that it is not hampered by elbows in the pipe or long lengths of pipe. Despite this ability, the device cannot remove certain types of clogs and there are some clogs that the device actually dislodged and then moved further down the pipeline where they became a problem again. Operation of the device also requires the use of large amounts of water which flow away down the pipeline and as such cannot be brought back and used again by the device [18]. Another technology for unclogging pipelines was developed by Ridgid Tool Company. This technology uses a blade which is driven along on the end of a 150 ft flexible metal rod. This technology is also low cost and can be quickly deployed. Unfortunately, the structure of the device has a few inherent limits. The blades themselves cannot clear out the entire clog within a 3 inch waste pipe because of their 12 | P a g e configuration, it has a tendency to break on hard clogs, and it s length limits how far it can travel to reach a clog [18]. Nature inspired another unclogging technology that was developed by NuVision Engineering Inc. This technology simulates the erosion of beaches that is caused by the motion of waves. The device removes most of the air below a clog in a vertical pipe and then allows fluid to enter and fill the pipe. The vacuum that results from the removal of the air is not perfect so some air is left trapped under the clog. The device then provides pulsations which create waves near the clog and are used to erode the material and clear out the clog. This device is capable of dealing with elbows in the pipes, was proven to work at 100 psi which is a lower pressure than used by other technologies, and the water can be replaced with a solvent in order to help eat away the clog faster. The drawback to using this device to unclog pipes is that it is very slow at eroding the clogs, much like waves take a long time to erode a beach. Another problem arises when deploying over extensive lengths of empty pipe where it becomes more difficult to establish the necessary vacuum to fill the pipe and create the waves [18]. 13 | P a g e 1.3.5 Simulating Plugs In short, the Pacific Northwest National Laboratory has extensive documentation on different waste simulants that are non-hazardous to the environment and are formulated to resemble the physical properties of radioactive plugs that occur in the pipelines. Waste simulants are used in the testing and development of waste treatment and handling processes. Simulants are all designed with a specific process in mind. For example, chemical simulants are used when it is necessary to mimic certain chemical properties. Physical simulants are used when the chemical make-up of the plug is of no relevance. There are many factors that contribute to the successful removal of simulants depending on the type of simulant. The mechanical strength, porosity, dissolution rate, solubility and thermal conductivity of the simulant are studied by DOE scientists. Simulants can be grouped into three major categories: sludge simulants, hardpan waste simulants, and saltcake waste simulants. Sludge simulants are thought to be the most prominent plug responsible for pipe clogs. Hardpan simulants resemble sludge-like material that has partially solidified. Saltcake waste simulants are designed to resemble plugs that have completely solidified. Low-pressure and highpressure water jets have both been used to remove blockages in pipes. In some cases mechanical cutting processes have been used. Due to availability, Bentonite Clay, a sludge type simulant was used for testing of the crawler s unplugging tool. Extensive behavior characteristics of this stimulant are well documented in a paper entitled Retrieval Process Development and Enhancements Waste Simulant Compositions and Defensibility. [30] Bentonite plugs as well as many other plugs were all suggested to Florida International University s Applied Research Center by the Department of Energy. They have undergone various tests over the years in different pipe configurations that have been laid out in the field of the Engineering Center. 14 | P a g e These blockages were used to assess the capabilities of the various unclogging technologies developed by different companies. As a result, it became possible to see that despite having certain abilities, these technologies (mentioned in 1.3.4) all had several weaknesses that would make them of limited use in the actual field. A properly designed crawler robot can have all of the desirable qualities of the other technologies and simultaneously have none of their weaknesses. Particularly, the issue of losing potency does not affect the crawler as it can use physical blades to destroy clogs like the Ridgid snake idea. However, it can be designed such that it will not have the limitations in distance that the snake has. Due to these factors, the need for a crawler robot that can unclog pipelines is established. 15 | P a g e 1.3.6 Radiation Effects The biggest threat to robotics in a nuclear environment is from exposure to gamma rays. Gamma rays which are similar to x-rays have short wavelength photons, the difference between them is that gamma comes from nuclear interaction and x-rays from electronic collision. There is protection from these photons by the uses of the tenth value thickness (T.V.T.) of material; this is the amount of material needed to obtain uncollided photons. Below the table shows the T.V.T. for the energy exposed to different material. Table 1: Photon tenth value thickness in cm for Al, Fe, Pb and concrete [25] Alpha and beta particles which can be stopped with the use of light shielding are non-treating to material properties exposed in that environment. When gamma rays are exposed to material they create two effects, ionization and atomic displacement. Ionization is caused in the second reaction from the ejection of electrons from the material due to photoelectric effect, Compton scattering and pair production; this causes a bulk amount of ionized material. In atomic displacement a cluster of defects is form from the kinetic energy causing the atoms to move. These two effects from gamma introduction threw the amount of exposure will change the displacement of certain material. 16 | P a g e 1.3.7 Effects of Radiation on Passive Materials In the following section it will describe the effect of gamma rays has on the following material; these values are only estimation on the effect of the materials. Inorganic Materials: The metallic structure of metals allows it to be resilient to high doses of radiation. Only after long periods of exposure to radiation is it capable to see properties changes in the material. Once the material is annealed it will retrieve its mechanical properties. The table below shows the damaged threshold of the most common metals used. Table 2: Radiation Damaged Thresholds on Metals [25] Ceramics is another material not as durable metal but has a better tolerance then organic material. The effect radiation has on ceramic materials is change in density causing the material to swell. The table below shows the damaged threshold of the most common ceramics used. 17 | P a g e Table 3: Radiation Damage Thresholds on Ceramics [25] Organic Materials: Radiation causes many effects on organic material due to the poor tolerance of the molecule configuration. In polymers the exposure to radiation causes the molecule chains to shorten and/or cross link chains. This reaction causes the polymers to be extremely sensitive to radiation. Most plastics have a degrading effect when exposed to radiation, which causes the material to be sensitive to mechanical stress. There is an amount of polymers banned from the nuclear environment due to the cause of the material to break down causing gases to be released effecting the properties of other materials in the environment or even the material itself. The table below shows the tolerances of plastics in the nuclear environment. 18 | P a g e Table 4: Radiation Tolerance of Plastics [25] A coating of thin polymer film is used in the radiation environment to provide easier decontamination, but like any polymer it also degrades with the amount of exposure of radiation received. The table below shows the coating used on various types of surfaces and the type of damages received with radiation. Table 5: Radiation Damages on Coatings [25] 19 | P a g e Exposure of radiation to adhesive because the damages to the chemical balance which in turn affects the bonding properties. The table below shows the effects radiation has on certain adhesive type. Table 6: Radiation Damages on Adhesives [25] Lubricates, another organic material, is also sensitive to radiation. Synthetic lubricants compared to natural or more resilient to radiation exposure. The exposure causes the lubricant to polymerize into a solid state, ruining the additives found in the lubricant, which results in the change in physical state. The table below shows the radiation tolerances of lubricant. Table 7: Radiation Effects on Lubricants [25] 20 | P a g e 1.3.8 Radiation Hardening When designing a new system for the nuclear environment radiation harden circuitry and material is need to tolerant the radiation effects in that environment. A radiation tolerant device is one that can receive accumulated dose of radiation while staying in stable conditions. Radiation hardening is usually performed to semiconductor devices to make them more tolerant to radiation. The devices compared to their non-harden copy has the same capabilities but the cost to the unit is more expensive. Radiation harden devices are only made by a limited amount of manufactures, which are usually used in military purposes but are provided to nuclear facilities. The advantage of radiation harden components is that they have been designed to be reliable and consistent. The design of a radiation harden device is costly due to the low customer base and limited amount of manufactures in that field. There are several techniques in creating a device that has a system that is tolerant to radiation. Annealing is a common way of allowing a robot to survive the process of radiation doses. With this process the robot can be run in a low dose area for a certain amount of time and then a high dose area for a certain amount of time, this allows the materials within the robot to stabilize. 21 | P a g e 1.4 Discussion With the tremendous responsibility of securing the radioactive remains from the Cold War, the U.S has stored millions of gallons of highly radioactive waste in underground tanks. Over time the radioactive waste has leaked from these single-shelled tanks contaminating soil and groundwater along the Columbia River. The DOE has responded by transferring the highly radioactive waste from the leaking single-shelled tanks into secure double-shelled tanks to prevent the further threat to human life. During the transfer process of nuclear waste, clogs/plugs have formed in the transfer pipelines and treatment facilities. Current technologies prove to be quite ineffective thus a new technology is needed to aid with the timely transfer of radioactive waste. 22 | P a g e 2. Project Formulation 2.1 Overview As the Hanford Site moves into a more active retrieval and disposal program, the site engineers will be encountering increasing cross-site pipeline transfers with a corresponding increase in the probability of a pipeline getting plugged. Not only will there be an increase of plugs in cross-site pipelines but also treatment facilities will experience an increase in pipe clogs. In the past, some of the pipelines have plugged during waste transfers, resulting in schedule delays and increased costs. Furthermore, pipeline plugging has been cited as one of the major issues that can result in unplanned outages at the Hanford Waste Treatment Plants, causing inconsistent operation. As such, the main objective of the peristaltic crawler is to provide a pipeline unplugging tool/technology to ensure smooth operation of the waste transfers and to ensure Hanford tank farm cleanup milestones are met. 2.2 Project Objectives The pneumatic crawler will be capable of applying enough force to pull its own weight, including the tether line, while maneuvering through 90 degree bends at a 4.25 inch radius. The crawler will be agile and be able to crawl through horizontal and up vertical sections of the pipe. An abrasive tool will be mounted to the front of the crawler for removing clogs. 23 | P a g e 2.3 Design Specifications (Final Crawler) 2.3.1 The crawler The crawler uses two rims that serve different purposes and are slightly different in design. For the final design, it is no longer necessary to have thinner sections to allow for mounting of the inner and outer bellows, neither are there any clamps used to attach them. The stainless steel bellows will have flanges on the ends which allow them to be bolted on directly. As a result of this, the two rear step downs were eliminated for the final design of the rims, leaving them at a length of 2.5 inches each. A set of four countersunk bolts on each side will be used to connect the bellows to the rims. Figure 11: Final Rim vs. Prototype Rim Removal of these sections also comes with the added advantage of allowing for a larger hole to be bored through the rims. This will allow for waste to pass through with greater ease and it will also make it possible to move greater amounts of waste through the crawler in shorter periods of time. 24 | P a g e Figure 12: Bore and Ports of Final vs. Original Rim Another difference is in the way the inner tubes for the rims are fed. In the original design, the feeds for the dual inner tubes used on both rims are in series, both output ports are fed by the same air line. For the final design, they are in parallel such that each port has its own air line. The ports on the final rims are offset from each other for this reason. The multiple input ports can be seen in the Figure 12. The offset output ports are shown in Figure 13. Figure 13: Multiple Output Ports 25 | P a g e Both rims of the crawler are made of 516 stainless steel. The prototype rims were for testing the capabilities of the crawler and were made of 6061 aluminum. This material would not survive in the high temperature radioactive environments found within the pipelines. However, 516 stainless steel can resist 1x1011 Gy. This material is considerably harder and tougher than aluminum and takes more time and effort to machine. However, using CNC lathes, the design can be preprogrammed and the time for making each rim is drastically reduced, allowing for these rims to be mass produced. As stated, the crawler will now hold a total of four inner tubes, each of which is independently pressurized or deflated. As proven by previous prototypes, the crawler is perfectly capable of maneuvering through pipelines using just two inner tubes, one per rim. Having four independent inner tubes serves as an added safety measure should an inner tube fail. The material of these inner tubes has changed as well. The prototype s inner tubes were made of rubber; the final tubes will be made of polyurethane. Polyurethane was chosen because of its resistance to high radioactivity and high heat. Polyurethane is also more resistant to puncturing than rubber and thus is more likely to crawl around sharp edges safely. A custom designed c-type clamp has been implemented in order to securely fasten the inner tubes to the crawler bodies without having them tear or puncture while inflating. The c-clamps are shown in the figure below. As seen below the c-clamps have filleted edges to prevent puncture of the inner tube. 26 | P a g e Figure 14: Clamps to Secure Inner Tubes All of these modifications yield a device that is more rugged, will withstand harsher conditions, and is less likely to fail and become stuck in the pipeline. Again, if a crawler were to become stuck in a pipeline, it would become a plug itself. Even with this advanced design, it is possible that all of the inner tubes may rupture or the crawler may become jammed against something within the pipeline. In the event that this happens, the final crawler design would not be stuck. The reason for this is that a reeling system was added to the final design. The rear rim of the crawler has an eyebolt attached to it and a braided stainless steel wire is looped through it. This wire is reeled up onto a winch which allows for the crawler to be forcibly removed from the pipeline if necessary. Another wire runs from the rear to the front rim and this ensures that all of the crawler can be extracted if for some reason the bellows were to sever. The wire from the winch, along with all of the air and fluid lines going to the crawler are going to be contained in a thin sheath of smooth polyurethane such that there is only one line being pulled by the final crawler. All of this line will be on one reel attached to the winch. The idea behind this is that if the lines were left separate, they could bundle up and interfere with removal of the crawler as it is being 27 | P a g e reeled out. This also makes it easier for the crawler to go long distances within the pipelines without the lines becoming a hindrance. The winch will be fastened to the hook shown in the figure below. Figure 15: Rear View of Final Crawler 28 | P a g e Shown in the figure below is the final assembly of the crawler complete with all radiation hardened components. Figure 16: Final Assembly of Crawler Since the crawler is hollowed, as the plug material is set loose, it is driven from the front to the back of the unit by water. This also keeps the passage inside the unit clean. The diameter of passage through the unit can measure 1.25 inches. The figure below shows a cross section of the crawler indicating the passage of loose plug material from the front to the back. Figure 17: Waste Flow through Crawler 29 | P a g e 2.3.2 The Camera In order to aid in finding the plugs, a camera will be mounted on the final crawler. The camera used to help the crawler view any obstacles in front of it would be constrained by its ability to survive in a radioactive environment, and also by its dimensions due to it being mounted to the front of the crawler s rim. Research for adequate radiation hardened camera for this application resulted negatively due to the shapes available in the market. Some of the smallest dimension radiation hardened cameras had a minimum diameter of 2 and length of 4 . This is mainly due to the protection material for the radioactive environment. Not only were the dimensions inappropriate but the cost per unit was extremely high. Regular miniature video cameras units were able to satisfy the dimensioning issue but had a short life span when exposed to a radioactive environment. The size of these units is no bigger than a dime as seen below. Figure 18: Micro Camera [27] 30 | P a g e A camera with similar dimensions could be mounted recessed into the front rim of the crawler. To protect the unit from the outside environment, a clear radiation resistant polymer would be used as a window for the recessed camera. The camera will be functioning in a low lighting environment so for the lighting issue there would be an LED wired in parallel with the cameras power supply. The average cost for these mini cameras is $50 to $150 depending on the picture quality and color. The unit for the crawler unit: would cost $150 and have dimensions of 8mm high, 8mm wide and 8mm thick; weight is about 0.9 grams. The viewing of this specific camera is 240 T.V. lines of resolution with connections that allow the camera to be connected to any household television set or monitor. A power supply of only 7 to 12 volts direct current could be applied to the unit for proper functioning. The camera position on the crawler can be seen in the figure below. Figure 19: Camera Location 31 | P a g e 2.3.3 Basic Principles of Locomotion To understand how the crawler will move forward, a detailed explanation is given below. Note: The crawler illustrated below is not the final design and is meant only for the purpose of understanding how the crawler will move forward. Figure 20: The Crawler s Locomotion (1st Prototype is featured) 32 | P a g e 1: The crawler is in its neutral state. No air pressure or vacuum is supplied to any section. 2: Due to positive pressure, the inner tube mounted on the front of the rim is expanded thus anchoring the front body to the inner walls of the pipe. The inner tube on the rear body is collapsed. 3: Vacuum is supplied to the bellow bringing the rear of the crawler forward. 4: The inner tube on the rear body is then supplied positive pressure to anchor the back rim to the inner walls of the pipe. 5. The inner tube on the front body is contracted by vacuum thus releasing it from a fixed position. 6. Positive pressure is supplied to the bellow thus pushing the front rim forward while the rear rim is held fixed. Steps 2 through 6 are repeated to move the crawler in the pipeline. 33 | P a g e 2.3.4 Bellow/Annular Actuator Design The bellow which serves as an annular actuator can be considered the crawler s abdomen and is responsible for the locomotion of the crawler. As seen in Figure 21, the bellow will consist of an air cavity formed by the inner walls of a two walled bellow. Figure 21: Cross-Section of Bellow The overall pulling force and agility of the crawler is heavily dependent on the bellow section. Both positive and negative air pressures will be supplied to this cavity. Because a higher magnitude of positive pressure can be created within the bellow it will be responsible for pushing the head of the crawler forward as well as the tether line. Negative pressure will only be used to pull the rear body forward. It is vital for the bellow of the crawler to be very rigid, yet flexible in order to meet the project objectives. As per a conference call with Dean DellaCecca, President/Chief Metallurgist, and Brad Schultz, Design Engineer, at Duraflex, Inc. [26], it has been determined that the bellow suitable for this application would be a custom made, edge welded bellow similar to the one seen below. 34 | P a g e Figure 22: Example of an Edge Welded Bellow The bellow will be made from stainless steel, a material that shows excellent resilience in a radioactive environment. The bellow will be rated for both positive and negative pressure. Most importantly it will be designed to have the flexibility needed to negotiate 90 degree bends having a 4.25 turning radius. The collapse ratio will be 8:1. This collapse ratio will give a 12 bellow a 1.5 length when collapsed. Theoretically this means for each sequence of expansion and contraction, of the bellow, the crawler will move 10.5 inches. The length of the bellow is an important factor with relation to its ability to turn corners. In order to feed air to the inner tubes on the front rim, steel braided 1/16 hose will be coiled inside the air cavity of the bellow shown below. Stainless steel woven hose is chosen to prevent the tubes from crushing while the bellow is compressed. Figure 23: Cross-Section of Bellow Showing Air Lines 35 | P a g e 2.3.5 Pneumatic System The pneumatic system s main components will consist of an air tank, air compressor, vacuum source, five solenoid valves, and with tubing. A simple microchip will control the sequencing of pressurization/depressurization of cavities. The changes in pressure result in the translation of the vessel by peristaltic movements. To reduce the weight of the tether, the tubing size should be kept to a minimum, as five air lines will be fed to the crawler. It is recommended that polyurethane tubing with 1/16 ID and 1/8 OD be used, however for the air supplied to the bellow a 1/8 ID is recommended. Polyurethane tubing will be used as it is resistant to gamma rays. Each rim has two separate inner tube type balloons. The inflation and deflation of each inner tube is independent of the other. The benefit of having two independent inner tubes on one rim is not only for maneuverability but it also serves as a safe guard. In the event that one inner tube bursts the crawler can proceed forward with use of just one inner tube. If one inner tube fails to hold pressure and bursts, an alarm will be sent to the operator and the control valve for that air cavity will be closed. The figure below shows a schematic of the pneumatic system. 36 | P a g e Figure 24: Schematic of Pneumatic System 37 | P a g e 2.3.6 Hydraulic System The hydraulic system will be responsible for powering the abrasive tool located in the front of the crawler. The performance of the abrasive tool will depend on the specifications of the selected pressure pump, mainly the pressure per square inch (psi) and gallons per minute (GPM). These parameters will directly affect nozzle selection, as the size of the orifice will change accordingly. Below is a simple hydraulic schematic of the setup. Figure 25: Schematic of Hydraulic System 38 | P a g e 2.3.7 Failure Modes By taking advantage of its various design features, the final crawler design is capable of surviving various failures that the prototype could not. There are a few worst case scenarios that the final crawler should be able to get out of. These are: one or multiple inner tubes rupturing, the crawler becoming jammed in the pipeline against waste, a rim becoming detached from the bellows, or total failure where the air cavity between the bellows ruptures and the crawler can no longer move. There are multiple inner tubes on the crawler in order to provide optimal traction and as a safety mechanism should one of them rupture. If one of the inner tubes ruptures, the operator will know because each air and vacuum line has its own gauge and a sudden loss of pressure or vacuum immediately indicates to the operator that an inner tube has failed. The crawler can move forward and continue operation if one inner tube ruptures. If two rupture, one on each rim, the crawler can still continue its operation as the original design was proven to move with only two inner tubes. However, if three inner tubes fail, or if two fail on the same rim, the crawler will not be able to continue moving. In this situation the operator merely has to activate the winch and remove the crawler from the pipeline. The inner tubes can be replaced and the crawler may be sent back in, or another crawler can be sent in its place. If the crawler were to become jammed, there are a few ways to loosen it. The line going to the crawler will have an encoder on it so that the operator knows how far the crawler has travelled and at what speed it is doing so. Should the speed suddenly hit zero, or if the operator notices the line stops moving in when there is no plug, then it is likely that it is jammed. The operator can then deflate the front inner tubes and make the bellows compress such that the crawler moves back. If the crawler was compressed when it became clogged, then the operator deflates the rear tubes and expands the bellows, again causing the crawler to move back. Should both of these attempts fail, then the operator may activate the winch and remove the crawler by force. Also, in the event that only one rim is jammed and comes 39 | P a g e apart from the bellows when the operator tries to free it, the winch will again be able to remove the crawler from the pipeline. The worst failure scenario is a rupturing of the air cavity between the inner and outer bellows. If this happens, the crawler may completely lose its locomotion. However, if the air leak is not too large, it is possible for the crawler to remain operational and the operator would know this by seeing a small loss of pressure on the bellows gauge. If the crawler continues to draw the line, then the unplugging operation may continue. It should be noted however, that the final bellows will be made of stainless steel and so it is not very likely that anything within the pipelines will be able to rupture them. This sort of failure is more likely to occur after the crawler has been in use for many cycles and over long periods of time at which point the steel may start to wear. In the event that this does take place, again the operator simply resorts to removing the crawler with the winch. Once the crawler is removed, if it is determined that it failed due to wear, a new one will be used in its place. Realistically, it is difficult to determine how long it will take to wear down the stainless bellows until the crawler is actually deployed in the radioactive waste lines and tested. However, it is likely that each crawler will withstand multiple uses. If it were to only make one trip and remove one plug, it would still be worth it as the normal means of removing a single plug costs millions in taxpayer dollars. 40 | P a g e 2.4 Constraints and Other Considerations A few physical constraints exist as the underground pipelines have an inner diameter of approximately 3 inches and a pressure rating of 300 psi. The crawler will be designed within these constraints. Due to the radioactive environment, the crawler s materials and components need withstand radiation. The complexities and expense of radiation hardened electronics will be avoided except for use of a camera. Instead a simpler pneumatic crawler is preferred whose electronic systems will be located outside of the pipeline. 2.5 Discussion A pneumatic crawler has been designed for the purpose of removing radioactive plugs is designed. The pneumatic crawler will need to travel through the rigors of radioactive pipelines having a diameter of approximately 3 inches and possessing multiple 90 degree elbows with the possible occurrence of vertical sections. Through simple geometric evaluation and the aid of SolidWorks it has been proven that the design and length of the rims will be able to go through the narrow 90 degree turns. Also because pneumatics is used as the source of locomotion there is a need for flexible elastic-type materials. Because of this, wear is a major issue, not just radioactive wear, but wear caused by friction due to the constant interaction between the elastic material and the inner surface of the pipe. This project requires proper material selection and coatings that will reduce the issue of wear. Proper material selection for the crawler is done to maintain the workable life of the crawler. After the crawler removes a plug, it will be retracted into a lead garage type compartment to prevent the spread of contamination. The crawler s components can be either properly disposed of or refurbished. 41 | P a g e This project requires that redundancies be implemented to maintain the integrity of the crawler. Fail safe modes must also be established to guarantee a drawback method incase the crawler becomes a plug itself. All data taken from testing will determine the mobility of the crawler, effectiveness of the abrasive tool, and maximum distance the crawler can travel. Data can be used to extrapolate and find the max distance it can travel. The weight of the tether will be kept to a minimum. Stress studies will be done to ensure the crawler is robust and can handle the rigors of the pipeline unplugging task. 42 | P a g e 3. Design Alternatives 3.1 Design Alternate 1 Figure 26: Alternative Crawler 1 This crawler design uses tank style tracks in order to propel itself. Each track is supported by four arms, each of which contains a gear on either end and a belt in between which connects the two gears. Each opposing set of arms has the inner gear connected to that of the other by a shaft such that both sides can be driven by one motor. In this way, each body section contains only two drive motors. Each body section has two sets of tracks with each set at 90° angles to the other. These tracks are placed such that the crawler will easily fit within a three inch diameter. The crawler can be made to turn by having two adjacent tracks spin their wheels in one direction whilst the other two spin in the opposite direction. In between sections, there is a ball joint which allows the device to flex in any direction necessary. This ball joint is covered by a flexible sheath; this sheath is the black piece in Figure 26. Each body section contains the necessary electronics for controlling the motors that drive it, along with wiring that travels out of the section to the adjacent ones in order to connect them all. The front end of the crawler will contain a larger motor in center which will be used to spin a drill head in order to remove clogs in the pipelines. 43 | P a g e 3.2 Design Alternate 2 Figure 27: Alternative Crawler 2 The second crawler alternative consists of multiple body sections shown in Figure 27. Each main section has arms which have wheels on the ends. These wheels are mounted at angles to each other such that when they spin they cause the crawler to twist and move forward in much the same way as a screw. The main internal components of these main sections are motors, gears, and belts for driving the wheels of the crawler. Each of these main sections is connected via a ball joint to cylindrical sections which contain the electronic controls for the system. Much like alternative one, the front main section has a drilling attachment. This requires that the front main section contain a larger motor for powering the drill as well as the small motors and components for driving the wheels. Theoretically, the very twisting motion of this crawler robot will allow it to change directions within the pipe bends. 44 | P a g e 3.3 Design Alternate 3 Figure 28: Alternative Crawler 3 The final alternative crawler seen in Figure 28 uses arms in order to move forward as opposed to the wheels used by the other designs. In order to move forward, the legs on the rear section will open and grab the inside of the pipe. The intermediate section is actually an actuator shaft with a ball joint in the center. The actuator will push the two front sections of the crawler forward, the front legs will then grab the pipe, and the rear legs will close and release the pipe wall. The rear section will then move forward, its legs will grab the pipe wall once more and the procedure will repeat itself. In order to turn at pipe bends, the crawler will employ a set of four rods between the middle and front sections which is capable of pushing the front forward such that it changes its angle with respect to the rest of the body. Each leg has gear teeth cut into the curved portion where it attaches to the body of the crawler. Within, motors will drive gear sets that cause the opening and closing of each leg. A specially designed planetary gear set will drive all four legs at each end such that only one motor is necessary for each set of four legs. As in the other designs, each body section will contain the necessary electronics and components to drive 45 | P a g e the crawler and allow for control of the motion. The front end will have a shaft that goes through the front gearset but does not engage it, such that a motor mounted in the middle can power the drill head without interfering with the functions of the leg system. This gear set will also have a different input location such that the motor that drives it can be offset from the shaft and the drill motor. 3.4 Feasibility Assessment Although there are other designs that can perform the task of traveling through pipes and removing plugs, they all have marked disadvantages as compared to the chosen crawler. The main issues with the other crawler designs are their mechanical complexity, the electronics, and the means they use to propel themselves. All of these factors were taken into consideration when choosing the pneumatic crawler. The pneumatic design is considerably simpler as far as the structure goes, it does not contain any electronics besides a camera, and the means it uses to move through pipes presents less problems. The first of the alternative crawlers has a complex structure which would require sophisticated electronics and mechanisms. It would need to contain an assortment of gears, belts, and motors just to drive the tracks. The arms supporting the tracks would have to be small, yet contain a gear on both ends and a belt running between the two. The belts themselves would have to be made of a strong material and would have to be held in tension. The motors running the tracks would have to provide the appropriate balance of torque and rpm to allow the crawler to pull its own weight at a reasonable velocity and to allow it to push forward as it drills through a plug. This brings up the second issue with this crawler, the track wheels would have to provide enough friction to grab onto the insides of the pipes. Should the crawler lose traction while working against a plug due to a slippery pipe surface, the device would be stuck in the pipe with little means for escape. This crawler also requires complex electronics and programming. It would be necessary for each section to have the means to power its 46 | P a g e motors which would mean batteries or wires coming from outside of the pipe. Each section would likely have to contain motor controllers and circuits to control the directions of motor rotation. Due to the levels of temperature and radiation encountered within the waste transfer pipelines, all of these electronic components would have to be radiation hardened and such components are rather expensive. The second crawler alternative suffers from much the same problems as the first. It would use complex electronic controls and require several motors. This design also uses fewer wheels than the first so there is a higher risk of losing traction and being lost within the pipes. Also, the twisting motion which this crawler uses in order to move forward would mean that it would be easiest to power it with batteries. These present their own problems within a radioactive environment as well as adding an extra risk of losing the crawler. Should the batteries fail, or run out of power, the crawler would be lost. Running the device on batteries would also require electronics for remote control of the device. Obtaining electronics that would allow for remote control of a device within a highly radioactive environment would be very expensive. It is possible to use a slip ring in order to attach a power wire to the crawler. A slip ring is a device that allows for the transfer of electricity from one side to another while allowing for one or both sides to be rotating. This slip ring would have to be custom made for the robot and would take up extra space within the device. Pulling the power wire along with it would also make it harder for this crawler to move through slippery pipe walls. The final crawler alternative solves one of the problems of the first two but creates its own set of issues. This crawler design uses legs to grab the walls of the pipes and push itself forward. These legs have sharp ends which can grab the walls of the pipe quite well and force the device forward regardless of whether the pipes are slippery. However, this way of moving the crawler means that the legs would be subject to wear over time, particularly considering that some of the waste within these pipes can be 47 | P a g e abrasive. Eventually, this would lead to the legs losing their efficiency and leaving the crawler stuck within the pipes as can happen with the other two designs. Also, moving these legs is a challenge in and of its own. If each of these legs was powered by its own motor, the cost of electronics would rise considerably and space constraints could mean that such a means of powering them is altogether impossible. For this reason, it is necessary to design gear sets that would move sets of four legs at a time. Each of these gear sets could become quite complex, and the design of such gear sets could be a senior design project in and of its own. The bending and wear of each gear would have to be calculated, shafts would have to be designed for holding each gear, each of these shafts would require complex analysis and reactions would have to be found in order to choose appropriate bearings for them. Then there is the issue of finding all of these components. Each of the components would have to withstand the load being applied whilst still being small enough to fit within the 0.75 inch diameter of the crawler body. This last issue alone can completely disqualify this crawler design for use within these pipelines. Due to all of these issues, the pneumatic crawler was chosen as the best possible design for the purpose of unplugging waste transfer pipelines. The pneumatic crawler completely eliminates the issues and costs presented by electronics as it does not contain any. All of the electronic devices requires for controlling its mechanisms can be located at the control unit outside of the pipeline. All that would have to run to the crawler from the outside is the lines for air and oil that drive the body and the drill. This design also eliminates traction issues caused by the other crawlers. The pneumatic crawler can grab onto the pipe walls by inflating air bags and then pushes against them in order to move forward. This method easily overcomes slippery pipes and will not suffer from wear like the legs of the third alternative crawler. The final advantage of the pneumatic crawler is cost. All of the crawler alternatives use expensive electronics and as a result it would be ideal to reuse them. This would mean that they would have to be decontaminated and stored in between uses. This process alone would drive up operational costs. The pneumatic crawler is simple enough that it can be produced in large numbers at 48 | P a g e an acceptable cost. Whenever one is needed, it can be used and then disposed of. When the need for one arises on another occasion, another crawler can be sent in. 3.5 Proposed Design The proposed design is a rather simple device that consists of three main parts. These parts are the double bellows in the center and the two end rims. Both of the rims have inner tubes attached to them. These inner tubes can be inflated or deflated via an air cavity that will run through each rim and exit under the inner tube. The inner tubes can expand to a diameter larger than the internal diameter of the pipe which means that once inside, they will easily grab the inside of the pipe wall and provide a secure hold for the crawler- this holds true regardless of how slippery the pipe walls are. Although both rims have this function in common and their overall shape is rather similar, the two rims differ. The rear rim has five air inputs which will be used to provide or remove air from the crawler. Two inputs will feed the rear rim itself, the other will feed the double bellows, and the last two inputs will feed the front rim. These inputs will all be threaded to 1/8 inch NPT such that pressure fittings can be added to them in order to connect the air hoses. The front rim will simply have two air inputs for receiving air from the rear rim. A hydraulic line will be mounted to the front of the crawler. The hydraulic line will be used to power the abrasive tools that will be tested on the crawler. This is another way in which the front rim differs from the rear; it will have provisions for mounting an abrasive tool. There are two different designs under consideration for the front rim. One design simply has threaded holes that allow for brackets to be attached such that various abrasive attachments may be used. These will range from pressure washers to a device similar to a sprinkler head which can spin an auger or other drilling tool. This rim will use a hydraulic or liquid feed for powering these tools. The second rim design incorporates a center ring and an air feed for mounting an air powered die grinder. This grinder has a chuck which allows for the mounting of various drilling tools. The grinder will be offset such that the end of the tool 49 | P a g e mounted to it will be flush with the end of the rim. The rim will have a conical section bored out of it such that the waste material being pushed back by the abrasive tool will slide smoothly into the rim and out towards the rear of the crawler. These rims will provide the traction necessary for the crawler to move through the pipeline. The double bellows will provide the forward motion for the crawler. It consists of a larger, outer bellows which contains a smaller, inner bellows. An air cavity is formed between the two bellows and this cavity will be filled with air in order to expand the bellows and the air will be removed in order to compress the bellows. The feed lines going to the front rim of the crawler will also run through this air cavity such that they do not interfere with the waste material going through the center of the crawler. 3.6 Discussion The basic idea is that the crawler will be inserted into the pipeline and the inner tube on the rear bellows will be inflated. This will give the rear of the crawler a hold on the pipe. From here, the bellows will be expanded. When the bellows reaches full expansion, the front inner tube is inflated in order to give the front of the crawler a hold on the pipe. The rear inner tube is then deflated, the bellows is compressed such that the rear rim is pulled forward, and the process is repeated from here. When a plug is reached, the rear inner tube will be inflated, the abrasive tool will be activated, and the bellows will be expanded. This will cause the crawler to push the abrasive tool forward into the plug material. If the plug is long enough, the crawler can be made to move forward as it continues to drill. As the crawler moves forward, the waste will go through the center of the crawler. The forward motion of the crawler will cause it to scoop the waste into itself and it will then eject the waste from the rear when it compresses. In this way, the crawler can move itself about the pipeline and attack any plugs that it encounters. 50 | P a g e 4. Project Management 4.1 Breakdown of Work into Specific Tasks The following are major aspects of this project · Literature Survey of available crawler s · Manufacturing and construction of prototype · Construction of the pneumatic system · Construction of test bed and simulant plugs · Implementation of hydraulic systems · Test results and data · Engineering design and analysis 51 | P a g e 4.2 Organization of Work and Timeline Figure 29: Gantt Chart 52 | P a g e 4.3 Breakdown of Responsibilities among Team Members Each group member will collaborate in all aspects of the project. These are their main roles: Lee Brady s major contribution was to the overall design of the crawler as well as the pneumatic control operating systems. He also was responsible for the ordering and acquisition of most components. He supported in the construction of the test bed, crawler, and simulant plugs. Jose Matos major contribution was the selection of proper materials and prototype manufacturing. He supported in the construction of crawler and the fabrication of simulant plugs. Brian Posse s major contribution was as that of a test engineer. He recorded and analyzed data. He supported the construction of test bed, crawler, and simulant plugs 4.4 Number of Hours Spent on Project Table 8: Project Hours Task Research and Development Report Writing Prototype Construction Testing Presentation Total Hours Spent on Project Hours Spent By Each Member Lee Brady Jose Matos Brian Posse Total Hours Per Section 100 68 80 248 70 70 70 210 40 70 50 160 50 56 50 156 5 5 5 15 265 269 255 789 53 | P a g e 5. Engineering Design and Analysis 5.1 Kinematic Analysis The device propels itself by the pressurization/depressurization sequence of the flexible cavities (balloons) located at the front, center, and back of the unit. Individual pressurization of the front or back cavities results in anchoring the system to the pipeline. This is a result of the linear relationship between the normal force imposed by the balloon on the inner surface of the pipeline and the resulting friction force governed by the equation: (1) Where: is the force exerted by friction, is the coefficient of friction, which is an empirical property of the contacting materials, is the normal force exerted between the surfaces The sequence of motion starts by inflating the rear cavity of the unit to anchor the device to the pipeline. The center cavity is then inflated to increase its volume which pushes the front end of the unit forward. Finally, the front cavity of the unit is inflated and then the center and rear cavities are deflated to complete once cycle of peristaltic motion. Figure 30 shows a simplified representation of the process previously described. 54 | P a g e Figure 30: Basic finite element analysis (FEA) representation of pressurization sequence on a simplified model 5.2 Finite Element Analysis The numerical modeling of the Peristaltic Crawler was performed using Finite Element Analysis. Analysis of stress distribution around a body can be performed by using a numerical technique that allows finding the solution of partial differential equations. One approach to obtaining an approximate solution to partial differential equation is the Finite Element Method (FEM). By applying the FEM to a problem, its originally constituent differential equations can be replaced with a formulation involving a set of algebraic equations in discrete values of the unknowns at a finite number of degrees of freedom [20]. For the case of a material that exhibits linear elastic behavior, the principle of minimum potential energy can be applied to solve the displacement at each node: [ F ] = [ K ][d ] (2) 55 | P a g e Where, ne [K ] = å éK e ù ëû (3) e =1 And, E [ F ] = å é f (e) ù ë û (4) e =1 Finally the stiffness matrix: é K11 ê ê ê K ij = ê ê ê ê ê ë K12 K 22 K14 K 24 K 34 K15 K 25 K 35 K 44 SYM K13 K 23 K 33 K 45 K 55 K16 ù K 26 ú ú K 36 ú ú K 46 ú K 56 ú ú K 66 ú û (5) In the case of a material that exhibits a non-linear behavior, equations 2 thru 5 need to be coupled with strain energy potential calculations. The derivation of these equations is not included in this report. The next step to solve an elastic problem using the FEM is to prescribe the appropriate boundary conditions. Whereas the boundary conditions can be of the essential or natural type, Prescribing one boundary condition along the entire boundary of the domain is a necessary condition for making the solution unique [21]. Moreover, it is not sufficient to prescribe Neumann conditions on the boundary. To guarantee the uniqueness of the solution at least one Dirichlet boundary condition must be specified. The FEA analysis of the crawler was performed using the ABAQUS version 6.8. Due to the 1,000 nodes cap imposed by the version of the software, a simplified 2-D version of the crawler was modeled. The 56 | P a g e depth of the 2-D model was based on the inside circumferential perimeter of the pipe. The 2.75 in diameter yielded a depth of 8.64 inches. The stainless steel rims were modeled as rigid bodies and the inner tubes and accordion were defined as hyperelastic material. The choice of the constituent equations used to calculate the behavior of the hyperelastic material was based on the availability of data. Hyperelastic materials are described in terms of a strain energy potential, , which defines the strain energy stored in the material per unit of reference volume (volume in the initial configuration) as a function of the strain at that point in the material. There are several forms of strain energy potentials available in Abaqus to model approximately incompressible isotropic elastomers: the Arruda-Boyce form, the Marlow form, the Mooney-Rivlin form, the neo-Hookean form, the Ogden form, the polynomial form, the reduced polynomial form, the Yeoh form, and the Van der Waals form. Based on a study conducted by Sasso [22]on Characterization of Hyperelastic rubber-like material the Neo-Hookean form was selected. The form of the neo-Hookean strain energy potential is 3 where U is the strain energy per unit of reference volume; material parameters; - 1)2 and (6) are temperature-dependent is the first deviatoric strain invariant defined as + 7 57 | P a g e Where the deviatoric stretches and ; J is the total volume ratio; is the elastic volume ratio; are the principal stretches. The initial shear modulus and bulk modulus are given by 2 , (8) & (9) One of the main computational challenges of modeling the unit was establishing stable Dirichlet boundary conditions resulting from friction forces on a dynamic model. In other words, for the model to be numerically determinate at all times, there should at least one completely fixed point of the crawler to the pipeline without defining a pinned control point. The precise timing of the amplitudes of the magnitude of the pressure loads exerted on the balloons and its relationship to the friction forces becomes even more involved by the non-linear behavior of rubber. Figure 31 shows the simulation of the crawler on a straight section of the pipe. The total motion of the unit per cycle was 0.77 in on an 8 sec interval using a 2 in long accordion. The total displacement per cycle can be greatly increased by using a longer center cavity. It is projected that an estimated 6 inches per each 10 second cycle could be achieved (3.0 ft / min). For the modeling of the crawler thru an elbow, the representation of the unit had to be further simplified not to surpass the allowable number of nodes. In this case, the unit was propelled thru the using a differential of pressure from behind the unit. Figure 32 shows a snap-shot of the unit turning. 58 | P a g e Figure 31: Straight Motion of the Crawler Figure 32: Turning of the Crawler on an Elbow 59 | P a g e The evaluation of the ability of the crawler bodies to navigate through 90 degree bends was determined using SolidWorks. In the figure below, it shows the prototype s geometry negotiating the specified 90 degree turn. From SolidWorks it has been determined that in order for the body to pass through the bend having a turning radius of 4.25 with a diameter of 3 , the largest diameter of the crawler body must be 2.5 with a length of 2.5 . However the addition of the bellows requires that the rims be made 2.25 in diameter to insure the crawler bodies can travel through the bend. Figure 33: Validation of Turning Ability with respect to Geometry 60 | P a g e 5.3 Force Analysis 5.3.1 Anchoring Force of the Inner Tubes The next calculation of the capabilities of the crawler was about the maximum anchoring force that it can achieve to drag the tether line inside the pipeline. The maximum anchoring force is defined by the maximum friction force that the inner tubes can achieved against the pipeline. As explained previously, the friction force is a function of normal force resulting for the pressurization of the inner tubes. Figure 34 shows the plot of several pressures to establish a relationship between inflating pressures and drag force. The friction coefficient used to determine the friction force between rubber and steel was 0.7 Maximum pulling force (Lb) [24]. 600 500 400 300 200 100 0 10 20 40 120 300 Balloon pressure (psi) Figure 34: Maximum Pulling Force as a Function of the Balloon Pressure An additional variable that was involved in the modeling of different pressures was the wall thickness of the inner tubes. As the maximum pressure increased so did the thickness of the inner-tube wall to preserve the realistic integrity of the parts and mathematical stability of the model. As seen in the figure below the wall thickness equates to .38 inches. 61 | P a g e Figure 35: Inner Tube Thickness for Anchor Test An important note is that slipping of the unit was recorded for high pulling forces (1.167 in max for 600 Lb). This slipping distance needs to be considered in the total estimated forward velocity of the crawler. Figure 36 shows the set-up used to measure the maximum pulling forces. 62 | P a g e Figure 36: Pulling Force Test As indicated in the figure above, the inner tubes were inflated at 300 psi and a cable was attached and pulled at 600 lbs as indicated by the blue color at the end of the cable. 63 | P a g e 5.4 Stress Analysis 5.4.1 Stress on Inner Tubes Abaqus /Standard Student version was used to evaluate the von Mises stress in the rubber inner tube inflated at 300 psi. Rubber has an ultimate strength of 15 MPa (~2175 psi). It can be seen in the figure below that the von Mises stress is 1008psi, which is well below the ultimate strength of rubber. The final crawler will use polyurethane which has an ultimate strength of 38 MPa (~5511 psi). Figure 37: Inner Tube Stress 64 | P a g e 5.4.2 Stress Analysis on Tool Support The crawler s tool support is possibly one of the largest areas of concern as far as stress goes. This tool support must not only hold up against the shock that is initially applied by the pressure washer going off, but it must also pull the full weight of the crawler s tether. The initial shock applied by the pressure washer nozzle when it is turned on is rather light, a thin plate of 0.117 in thickness can more than withstand this shock. The true issue arises when it comes to pulling the tether. Originally, the idea was to have the rear rim pull the weight of the tether forward; however this would mean that the compressive motion of the crawler would be pulling the tether forward, excluding the pressure washer hose which is attached in the front. The maximum vacuum force that can be generated would eventually be too small if the crawler had a long enough tether. The maximum pressure that can be added to the crawler for the purpose of expanding it is considerably larger and would be capable of pulling the tether forth even over extended distances. For this reason, it was decided to strap the airlines to the pressure washer hose in the rear of the crawler. In this way, the crawler pulls the tether forward when it expands. However, this means that the tool support must be capable of sustaining the full load applied by the tether. An initial study was run using the final rim design loaded with a 50 lb normal force and restraining the rim in the inner tube area. The design was somewhat simplified in order to allow for faster meshing. The study was run using successively smaller mesh sizes until the factor of safety values began to fluctuate near a single value. The results show that the thin plate design was rather weak, never exceeding a factor of safety of 0.63. This value means that the plate would most certainly fail over time and it would not be able to handle the weight of the tether over long distances. It was projected that an ideal plate would be able to pull 345 lbs of tether. By using the results of the initial testing, the plate was modified, making it an inch in thickness and adding fillets where it meets the inner walls inside the rim. Tests were then performed in the same manner as before, except that the tool support was 65 | P a g e now loaded with 350 lbs of force, 5 more than the ideal. Upon completion of testing, a final factor of safety of 5.2 was obtained for the new tool support design. Figure 38: Initial Tool Support, 50 lb load, 0.05 in. Mesh Size 66 | P a g e Figure 39: Initial Tool Support 0.05 in. Mesh Size Figure 40: Final Tool Support, 350 lb Load, .05 in. Mesh Size 67 | P a g e Figure 41: Final Tool Support 0.05 in. Mesh Size Although the results of the analysis performed in Cosmosworks were satisfactory, it is not advisable to simply rely on one program. In order to verify that these results are indeed accurate, the study was repeated within Ansys Workbench. Using the same final mesh size and applying a load of 350 lb, the minimum factor of safety obtained through Ansys was 6.8 which is slightly higher than the factor returned by Solidworks. It is normal for the results of studies performed in different programs to vary, the deciding factor as to their accuracy is whether the results are close to each other. The factor of safety values returned by the two programs are close to each other. Further verification was obtained by comparing results for stress and displacement between the two programs. The results of the stress and displacement plots obtained from both programs are also rather close. Table 9 is a chart of value comparisons between the two programs. Table 9: Ansys vs. SolidWorks Results SolidWorks Min Max Ansys Min Max Stress Displacement FOS (psi) (in) 5.236 1.419 3.94E-32 10 5679 0.0001589 6.8148 5.188 0 15 5320 0.00015695 68 | P a g e Figure 42: Von Mises Stress in Ansys (Exaggerated Deformation Scale) Figure 43: Von Mises Stress in Solidworks (Exaggerated Deformation Scale) 69 | P a g e 5.5 Deflection Analysis Cosmoworks has the capacity to generate displacement charts for parts that stress testing is performed on. Once the stress testing on both the initial and final tool support designs was completed, a displacement chart was generated for the tool supports at the final mesh size. The results show that the first tool support would deflect 2.52x10-3 in under the 50 lb load applied to it. The final tool support design proved to be superior yet again, deflecting only 1.589x10-4 in, under a load of 350 lb. Much like the stress and factor of safety, the values obtained for the deflection test were verified in Ansys. Figure 44: Initial Tool Support Displacement 70 | P a g e Figure 45: Final Tool Support Displacement (True Scale) Figure 46: Ansys Displacement (Deformation Exaggerated Scale) 71 | P a g e 5.6 Material Considerations 5.6.1 Crawler Materials Material selection is a primary concern in the design of a unit that will be exposed to a high level radioactive environment. For the case of hyperelastic material previous research has been conducted to study the decay of their mechanical properties when exposed to radiation. One study by Yakubisin [23], investigated the effect of gamma and neutron radiation on polymers. The threshold for material failure was set on a strength decay of 25%. Of the 15 polymers studied, all show moderate decay of their properties when radiated. Figure 477 shows the dosages imposed on the tested samples of the material. Based on the required performance and shapes that the parts will undergo in the crawler, polyurethane shows to be a potential candidate in the material selection for the flexible bodies. Its rate of exposure before failure is 4 X 109 rad. Once the unit is deployed in the field, it will be necessary to keep a record of hours of operation under HLW environment to establish the maintenance schedule of the unit. 72 | P a g e Material vs. Rad 1.00E+10 1.00E+09 1.00E+08 1.00E+07 1.00E+06 1.00E+05 1.00E+04 1.00E+03 1.00E+02 1.00E+01 1.00E+00 Kel-F Elastomer Neoprene Elastomer Nitrile Rubber Viton A Teflon Kel-F Epoxy Nylon Silicone Resins Epoxy Resins Phenolic Resins Glass Fabric reinforced Glass fabric reinforced Glass fabric reinforced Polyurethane Polystyrene Figure 47: Radiation Dosage Required for 25% Damage Polyurethane is to be used for the expanding inner tubes of the final crawler design; however it will not be used for the bodies. Both of the rims for the crawler and the annular actuator that will serve as the bellows for the final design are to be made of grade 70 516 stainless steel. This material was chosen for the construction of the final design crawler because of its ability to survive in a radioactive, high temperature environment. The US Department of Energy has conducted extensive studies into the use of various materials for the construction of high level waste tanks and decided to use grade 70 516 steel. These include studies to determine how the materials fare against stress-corrosion cracking, the appropriateness of their nil-ductility transition temperature for the environment, and how their other material properties hold up against the environment. The original high level waste tanks built for DOE sites were made of lower grade steels and they eventually leaked, mostly because of cracking. At the DOE Hanford site, tanks are exposed to amounts of gamma radiation below 1000 rad/hr. This amount of 73 | P a g e radiation can alter the properties of materials that are exposed to it by knocking atoms out of their normal sites. After the 1960s, tanks were made of 516 steel and these tanks have never leaked. The tanks have a design life of 50 years and studies performed for the DOE have shown that 516 stainless tanks will not be affected by the radiation over this time period. Further studies have shown that a minimum of 0.2% chromium within the material composition of steel used in this environment can reduce wear and corrosion considerably in the tank environment. 516 meets this requirement and on average its corrosion rates are very low, generally less than 0.5mp in the tank environment. ASME SA 516 was compared to SA 537 and chosen because there were no significant differences in strength and toughness; it met the minimum design requirements for construction of HLW tanks, and was of lower cost by approximately 5%. 516 has a yield strength of 38 kpsi and an ultimate tensile strength of 70 kpsi. At the 250 F temperature of the tanks it has the same maximum allowable stress and design stress intensity at temperature as SA 537. [31] 74 | P a g e 5.6.2 Camera Selection Studies have been performed on the use of charged-couple device (CCD) cameras in a radioactive environment. As specified on the presentation from the ThermoFisher Company a commercial CCD camera could last one hour at 300 Gy/hr [29]. Below it is see how the image is distorted one hour after being in a 300 Gy/hr environment. Figure 48: Images of the CCD Camera in a Radioactive Environment [29] The use of the camera chosen for the crawler is exposed to far less radiation as seen in the previous experiments. At the Hanford site the readings of the gamma radiation within the tanks are 1000 rad/hr [31] which equals 10 Gy/hr. More studies need to be done in order to verify just how long the video camera will last. However, another radiation hardened inspection device can survey where the blockage is in the pipeline. After, the peristaltic crawler can be sent in once the location and distance of the plug is known. 75 | P a g e 5.7 Cost Analysis 5.7.1 Material Cost Many factors contribute to the price of the final crawler i.e. the custom stainless steel bellow, the power of the hydraulic system and pneumatic system. As mentioned before in the report, plugs in a pipe are treated as a case by case basis; some clogs may need more powerful hydraulic systems to free it from a pipe. The materials and equipment below are suggested. Table 10: Cost List of Final Major Components Item No. Part Description Material Unit Price QTY. Total Price 1 Crawler Bodies 516 Stainless Steel 74.67 1 74.67 2 DuraFlex Inc. Custom Bellow Stainless Steel 3000.00 1 3000.00 3 Valve Solenoid 1/8" - 66.55 5 332.75 4 Gauge Manifold - 14.84 5 74.20 5 Simpson 4050V 4000PSI 5GPM - 2999.00 1 2999.00 2130.00 1 2130.00 6 7 Electric Air Compressor 80 GAL 16.5 cfm Welch High Vacuum Pump - 2000.00 1 2207.00 8 Pneumatic Hoses Polyurethane 0.47 2300 1081.00 9 Hydraulic Hose Polyurethane 590.00 8 4720.00 Total 16618.62 76 | P a g e 5.7.2 Labor Cost The labor costs associated with the construction of the prototype crawler is as follows: Table 11: Labor Costs Task Machining Prototype Construction Hours Cost/hr 210 50 50 20 Overall Labor Cost Total Cost 10500 1000 11500 (Note: The hours shown are a summation of hours put in by the all team members) The labor costs associated with the manufacturing of the final crawler design will be considerably lower than this. There are quite a few reasons for this; they include a reduction of labor hours and superior manufacturing processes. The prototype crawler was the first of its kind, and labor costs were increased due to various reasons. It was necessary to design the device without any prior experience in designing a device of this type. Once the design was complete, the rims were turned on a manual lathe. This process alone is rather time consuming, approximately six hours are required just to make the diametral features of each rim. With this completed, it was necessary to drill the various air holes in the rims with the use of an aircraft bit. Brass tubing was ground down and affixed to one hole in each rim to serve as connections for the airline going between the front and rear rims. Airtight putty was applied to the clamp recessions on each rim and the inner tubes and bellows were applied to both and held down with automotive c-v joint boot clamps. Upon completion of the machining and assembly, the crawler was tested and it was discovered that even though the individual rims fit through the 90 degree elbows in the test bed, the entire crawler assembly did not. This was because the bellows would affect the motion of the rims causing them to wedge against the elbow wall. As a result of this, the crawler was disassembled, the rims were turned on the lathe yet again in order to reduce their length and diameter 77 | P a g e and the process of putting the crawler together began yet again. This process added considerably to the labor hours, along with various assembly/disassembly procedures carried out in order to modify the configuration to avoid air leaks. All of these problems are eliminated by the final design. The necessary sizes for the various crawler components have been determined by testing and the final design is made such that it will never have to be disassembled for modifying the size. Also, the time consuming process of applying c-v joint clamps has been eliminated by the use of specially designed inner tube sleeves and clamps that are simply bolted on by a machine. The annular actuator used is bolted to the rims and then welded such that there are no clamps between it and the rims. Finally, the largest reduction in labor hours comes in the use of automated manufacturing processes to produce and assemble the parts that go into the crawler. A large scale CNC lathe can simply be programmed to build the rims in large quantities and an assembly line with robotic arms can accommodate the assembly process. 78 | P a g e 6. Prototype Construction 6.1 Description of Prototype The prototype crawler to be used for testing in this project differs only slightly from the final device which will be deployed at the Hanford site. The main difference between this crawler and the final crawler is the materials and bellow design. The final crawler will have 516 stainless steel rims and all the bellows, hoses, and assorted fittings will also be made from materials that can survive in a radioactive environment. The prototype crawler is made with aluminum rims and uses regular hoses and bellows. This is because the prototype crawler will simply need to serve as a test mule to verify that the design can crawl through a waste pipeline, negotiate 90 degree turns within it, can reach a plug at a desirable rate of speed, and can take on the toughest of plugs once there. The novelty of using peristaltic motion to successfully propel a device inside HLW lines creates the possibility of using the crawler as a vessel to carry unplugging technologies. By reducing the distance between the unplugging tool and the location where the plug formed, the success rate for removing the blockage is greatly increased. The unplugging tool attached to the prototype is a high pressure nozzle. Figure 49 show the crawler assembly with the nozzle attachment and a close-up of the nozzle. Figure 49: Nozzle Attachment 79 | P a g e The hydraulic auger attachment is a conceptual design. It consists of a hydraulic motor bolted to the front rim of the unit and a steel impeller for removing the plug. Since space is critical, a high torque sprinkler-like rotating head was selected to convert the fluid pressure into rotational motion. Also, the design uses the water exiting the head to keep the auger clean during drilling operation. Figure 50: (a) Crawler with Auger Installed, (b) Auger shows the crawler assembly with the auger attachment and a close-up of the auger. Figure 50: (a) Crawler with Auger Installed, (b) Auger Due to time constraints the high pressure nozzle design was implemented on the prototype crawler. Since the crawler is hollowed, as the plug material is set loose, it is driven from the front to the back of the unit by small water jets located along the circumferential perimeter of the pressure hose. This also keeps the passage inside the unit clean. The diameter of passage through the unit can measure between 1.0 to 1.5 inches. Figure 51 shows a cross section of the crawler indicating the passage of loose plug material from the front to the back. 80 | P a g e Figure 51: Cross Sectional View of the Crawler 81 | P a g e 6.1.1 Prototype System Description The complete system schematic of the prototype system is shown in Figure 52. In the prototype, air will be supplied from air ports located in the Applied Research Center (ARC) laboratories. The pressurized air coming from the air supply line will be directed to a manifold. An air pressure sensor will be located between air supply and the manifold to limit the maximum pressure into the line. The manifold controls the valves that are required for controlling the mode of motion of the crawler (back, anchor, or forward). Figure 52: System Configuration 82 | P a g e Figure 53: General Schematic of the Pressure Lines in the Pipeline 83 | P a g e 6.2 Prototype Design The structural design of the crawler incorporates the inner tubes on its outer rim and air tunnels that route air to specific locations. Figure 54 shows the back side of the rear rim. The back side of the rear rim is where the air hoses coming from the compressor enters the crawler. The left most inlet will lead to the inflation of the rear rims inner tubes. The middle inlet will provide an air passage to the bellows. The inlet on the right leads to the inflation of the front rim. Figure 54: Rear Rim - Back Side Figure 55 shows the front side of the rear rim. 84 | P a g e Figure 55: Rear Rim - Front Side Figure 56 is an illustration of the front rim. The front rim has just one inlet feeding the two inner tubes on its rim. Figure 56: Front Rim - Rear Side 85 | P a g e In Figure 577 a SolidWorks representation is shown. Figure 58 illustrates the assembly of the prototype crawler. Figure 57: SolidWorks Modeled Crawler Assembly Figure 58: Physical Crawler Assembly 86 | P a g e 6.3 Parts List Table 12: Parts List Item No. Part Quantity 1 12 Rod @ 2.75 O.D. 1 2 2 Black Air Duct Hose 1 3 Hoover Hose Assembly 1 4 Inner tube 1 5 Valve Solenoid 1/8 In 3 6 Manifold Gauge 3 25 ft 10 1/16 ID Polyurethane Tubing 1/16 x 1/8 NPT Barbed Tube Fitting Pinch Hose and Tube Clamp PICkit 2 Starter Kit 11 2600PSI Pressure Washer 1 12 Motor Head/Nozzle Head 1 13 1 14 Side-Jaw Pinch Clamp Pincer 1/4 Double Barbed Tee 15 Reducing Tee 1/4 x 3/8 x 1/4 2 16 Barbed 1/4 ID x 1/8 MNPT 6 17 Barbed 1/4 x 1/4 MNPT 2 18 Barbed 1/4 x 1/4 FNPT 2 19 Inline Mini Air regulator 2 20 C-v joint clamps 6 21 1/8 Square Plug 4 22 Hose Clamps 20 23 1/4 Tygon Tubing 15 ft 24 1/16 x 1/8 FNPT Adapter 3 25 Barbed Tee for 1/16 3 7 8 9 3 6 1 2 87 | P a g e 6.4 Construction There are several parts necessary in order to construct the crawler. The prototype crawler is composed of two rims, two inner tubes, eight c-v joint clamps, and various feed hoses. Figure 59: Crawler Bodies Unassembled The pressure and vacuum are fed to the crawler via three solenoid valves, each of which has a pressure and a vacuum input. There are three switches connected to the solenoid valves and each one is used to control a part of the crawler: one for the front rim, one for the rear, and one for the bellows. This setup was used to test the crawler motion and insure that it would move as desired. A few measures must be taken in order to assemble the crawler and get it to work as directed. The first issue is to make the front and rear rims. The overall shape and most of the features of the rims are made on a lathe using a metal cylinder. Both rims were designed such that they would have most of their outer shape being the same. The main difference is in the air feeds that must be drilled into each rim and the modifications the front rim requires in order to hold the abrasive tools. Both rims will be 88 | P a g e lathed first, which is the most time consuming and difficult aspect of the crawler s construction. With this part completed, they will be clamped down on a milling machine and the necessary holes will be drilled using an end mill. From here, the holes which required threading in order to allow for pipe fittings and attachments will be tapped to the appropriate thread size. Figure 60: Pneumatic Inputs Once the rims are complete, both will be attached to the inner and outer bellows. The inner bellows will slide over the end of one of the rims and leak proof putty will be applied between the bellows and the rim in order to provide a better seal. C-v joint clamps will then be used to secure the bellows onto the rim. With this part complete, the feed pipes for the front rim will be connected and the outer bellows will then be slipped over the inner bellows and secured to the rim in the same fashion. The inner bellows must then be attached to the other rim using more putty and c-v clamps, the feed pipe will then be connected to this rim, and then the outer bellows will be slipped onto this rim in the same way as the inner. 89 | P a g e Figure 61: a. Outer Bellow Over Inner b. Coiled Hose to Feed Front Rim The next step in the construction of the prototype is the attachment of the abrasive tool. For one of the front rim designs, brackets must be made for attaching the different tools it will use, these being the pressure washer nozzle. This tool must be attached to the brackets and the lines for providing them with fluid must be run through the bellows cavity in advance, before the front rim is attached. Figure 62: Pressure Nozzle Affixed to Crawler 90 | P a g e 6.5 Prototype Cost Analysis Table 13: Prototype Cost Analysis Table 13 lists all the essential materials to construct the prototype. However, several of these items do not need to be purchased as they will be provided by the Applied Research Center (ARC) or are already purchased. 91 | P a g e 7. Testing and Evaluations 7.1 Preliminary Testing This section covers the testing and evaluation stage of the crawler s materials and the feasibility of the design. This stage in the project is meant to understand and correct any issues with the design. A bellow material test was done to ensure the proper selection of bellow material. There were many bellow materials tested and researched for use on the final prototype. A double bellow test was performed to understand the function of the two bellows working in conjunction. A feasibility test was performed on a mock prototype. To understand the motion characteristics of the design, the mock prototype was used. 7.1.1 Preliminary Test Description The Bellow Material Test: During this test both positive and negative pressure was supplied into the bellow to test how the material contracts, expands, and holds pressure. The bellow is fixed to a jig and capped off on the other end. A bellow chosen for this application should expand and contract uniformly. The double Bellow Test: During this test two different sized bellows will be mounted one inside the other. A jig will hold the two bellows so that positive and negative pressure can be supplied in between the two bellows. The interaction between the two bellows will be noted. 92 | P a g e The Feasibility Test: During this test a mock prototype will be constructed to test whether the crawling concept works. The function of the valve operation and motion of the pneumatic crawler will allow us to understand and perfect the final design. 7.2 Preliminary Test Results 7.2.1 Results: Bellow Material Test: The first material tested was a hard plastic bellow used for household plumbing as seen below. Figure 63: Contracted View of the Hard Plastic Bellow Figure 64: Expanded View of the Hard Plastic Bellow 93 | P a g e This material performed well under vacuum and pressure but started to show material defects along the corrugated material as seen in the figure below. Figure 65: Defects on Hard Plastic Bellow The next material tested was the soft neoprene bellow. This material seems lose its integrity under pressure and vacuum. Figure 66: Neoprene Bellow Defect 94 | P a g e The best material tested is the thermo plastic air duct hose. As seen in the figures below this material was able to expand and contract without any flaws. Figure 67: Expansion of the Thermo Plastic Bellow Figure 68: Contraction of the Thermo Plastic Bellow The second best material found was the clear PVC air duct hose. This material was able to expand and contract semi uniformly. The only issue with this material is when contracted it didn t seem to hold its integrity quite well. Figure 69: Contraction of the Clear PVC Bellow 95 | P a g e Figure 70: Expansion of the Clear PVC Bellow The thermo plastic ducting hose provided the best performance to use on the final prototype; it provided the cleanest expansion and contraction of the material while still keeping its reliability and shape. 7.2.2 Results: Double Bellow Test: The bellows used where the 2.5 inch, 2 inch thermo plastic hose, and a 1.5 inch Hoover vacuum hose. The Hoover vacuum hose was considered because it has a very small diameter yet is very flexible; unlike all other 1.5 bellows purchased. The three different bellows can be seen below. Figure 71: Double Bellow Test Samples 96 | P a g e The testing jigs for the double bellow tests are seen below. Figure 72: Test Jig for the Double Bellow Test Figure 73: Modified Air Passage for the Third Combination Test The first tested double bellows configuration is the 2.5 inch thermo plastic hose with the 2 inch thermo plastic hose. They expanded as anticipated, but came across some problems of interference due to clearance issues within the two bellows. 97 | P a g e Figure 74: Contraction of the First Bellow Configuration Test Figure 75: Expansion of the First Combination of the Double Bellow Test Figure 76: Clearance Issue between the Bellows 98 | P a g e The second combination tested, was the 2.5 inch thermo plastic hose with the Hoover 1.5 inch vacuum hose. This configuration had a satisfactory outcome due to the excessively large clearance between the bellows. Figure 77: Contraction of the Second combination Bellow Test Figure 78: Expansion of the Second Combination Bellow Test Figure 79: The Clearance of the Second Combination Test 99 | P a g e The third combination was the 2 inch thermo plastic hose with the Hoover 1.5 inch vacuum hose. This combination also satisfied the test of expansion and contracting uniformly. The final prototype will use this combination as it allows for more space around the exterior of the crawler while still possessing enough clearance between the two bellows. Figure 80: Contraction of the Third Combination Bellow Test Figure 81: Expansion of the Third Combination Bellow Test 100 | P a g e Figure 82: Clearance of the Third Combination Bellows 7.2.3 Results: Design Feasibility Test Performed on the 1st prototype, the design feasibility test was conducted to test the function of the crawling motion of the unit. The pneumatic controls have been temporarily set up so that the basic function of the mock prototype can be performed. The front and rear rims share lines for both the vacuum and air pressure to the solenoids, while the bellow has its own supply. The solenoids are control by on-off switches allowing us to switch from vacuum to air pressure in sequence. Pressure is adjusted through the use of a gauged valve on the main air pressure line. 101 | P a g e Figure 83: Solenoid Setup with Plumbing and Controls Figure 84: Expansion of the 1st Prototype Figure 85: Contraction of the 1st Prototype 102 | P a g e Figure 86: Inner Tube Decompression Figure 87: Inflation of Inner Tube 103 | P a g e 7.3 Design of Experiments Description of Experiments for Final Prototype The testing of the unit will focus on studying the reliability of the device and validating its capabilities. To test the reliability of the peristaltic motion, the crawler will be put through scenarios in which it needs to perform successfully. The following are the key objectives for the testing phase: · Functionality: Checking proper functioning of the systems and principles of motion presented in the design. The crawler will be placed inside a clear pipe and will be operated using different pressure levels. Variables such as proper programming sequencing of inflation/deflation, proper time interval for each cycle, mitigation of any leaks of pressurized fluid will be controlled in this stage. · Agility: Since the DOE transfer and cross-lines are include turns and elevation changes, the crawler must be able to successfully navigate thru these obstacles. Using a test-bed consisting of straight sections and an elbow, the unit will be tested for clearing turns in its path. Measurements will be taken on the time it takes the crawler to turn across an elbow. · Force: The crawler uses pressurized air to power its propelling mechanism and pressurized water to power the unplugging tool. This requires dragging a two line tether of pressurized air and water as it crawls its way inside the pipeline. As the length of the tether increases inside the pipeline, so will the force required by the crawler to pull the tether. For this test, seen in Figure 85 the crawler will be hooked to a fish weighing device which will record the maximum pulling force it can achieved. Several pressure settings for the air pressure will be tested to record experimental data that can allow accurate calculations of the friction conditions between the 104 | P a g e crawler and the pipeline. Figure 88: Calculating Force · Speed: The crawler will be tested on its capability to travel distances that will go from an access point to the target location. This test will provide the estimated time that will take for the unit to reach a plug located straight down the pipeline. · Unplugging Ability: The effectiveness of the abrasive tool attachments to unplug simulant plugs will be studied. 105 | P a g e 7.4 Test Results and Data 7.4.1 Pulling Force The pulling force of the crawler is determined by the positive pressure cycle of the bellow. Since the double bellow is responsible for pulling the tether line its pressure values are paramount. Although the pneumatic lines are attached to the rear rim they will be fastened to the hydraulic line, which is secured to the front of the rim, in order to be pulled forward seen in the figure below. There is a great advantage of pulling the tether with positive pressure rather than negative pressure, as higher magnitudes of positive pressure can be achieved. Figure 89: Pneumatic Lines Fastened to Hydraulic Line The theoretical force can be calculated by the equation: The area that the two bellows create can be calculated by taking the area of the larger diameter bellow and subtracting the area of the smaller diameter bellow. See figure below. 106 | P a g e Figure 90: Area Created by Double-Bellow The test was conducted using a wench cable with one end attached to the bracket at the front of the crawler and the other on a spring scale. The figure below shows one trial taking place. Figure 91: Pulling Force Test 107 | P a g e Figure 92: Spring Scale The table below compares theoretical values to experimental values. A maximum pressure of 21 psi was attained on the prototype without compromising integrity. Table 14: Pulling Forces Pressure (psi) Theoretical Force (lbs) 10 17 21 40 50 100 150 200 250 300 11.51 19.56 24.17 46.03 57.54 115.07 172.61 230.15 287.69 345.22 Ave. Experimental Force (lbs) Error % 12.2 23.2 27.3 6.018 18.592941 12.97 108 | P a g e The difficulty of accurately measuring the bellows diameters may be responsible for these errors. However, if the bellows were inflated to 300 psi (maximum allowed for pipeline specifications) the theoretical pulling force would be approximately 345 lbs. 109 | P a g e 7.4.2 Vertical Crawling To prove that the crawler is able to crawl up vertical pipe sections, a pipe was held in the vertical position and the crawler was tested. Figure 93: Vertical Crawling 110 | P a g e 7.4.3 The Crawler s Speed Table 15: Prototype Crawler Speed Assessment Trial 1 2 3 4 5 Average Six feet (sec) 107 148 151 136 146 137.6 Six Feet w/ elbow(sec) 343 332 351 340 342 341.6 Elbow Clearance Time (sec) 236 184 200 204 196 204 Five trials were run to assess the prototype crawler s speed. This test was performed by placing the crawler into two different test beds. The first was a straight line consisting of two sections and the second consisted of two sections divided by an elbow. A measurement was taken from the front of the front rim of the crawler out to the end of the pipeline. The crawler was then run through the two test beds, with five trials performed for each test bed. A stop watch was set to measure the amount of time that this procedure took. An average time was calculated for each; also a time difference was taken in order to assess the average time it takes the crawler to maneuver a 90 degree bend. On average, the prototype can crawl 6 feet of pipe in 2.5 minutes. On average, it takes 3.4 minutes to maneuver through an elbow. Knowing that the straight test bed is six feet long and taking the average time that it takes to crawl through this length of pipe, it was found that the prototype crawler attains an average speed of 0.04 ft/s which translates to 2.4 ft/min. 111 | P a g e Figure 94: Straight Test Bed Figure 95: 90 Degree Test Bed 112 | P a g e 7.4.4 Unplugging Ability The prototype crawler was tested against Bentonite clay plugs. Two nozzles were used for this purpose. The first was a sewer nozzle with backward facing jets as well as a forward facing one. These are designed to propel themselves through pipelines, however it was hoped that the rear facing jets would serve to move waste back through the crawler. In test of the nozzle by itself, it pushed its way between the plug and the wall, creating a hole in part of the plug. Ideally, when mounted in the crawler, it would make such a hole in the center of the plug and then blast away at the parts of the plug against the walls by means of the rear jets. However, when the nozzle was tested on the crawler, it was found to be ineffective. The reason it had bored its way in before was actually because the rear facing jets physically forced it into the plug while also washing away some of the plug around it. With the crawler holding the nozzle in place, the nozzle was not able to do this and its forward pressure is lowered by the rear facing jets. A traditional 15 degree pressure washer nozzle was also tested individually on a sample plug. This nozzle destroyed the plug with relative ease when compared to the other one. When mounted on the crawler, the results remained the same. The nozzle quickly loosened up large chunks of the plug and then dissolved them. Some chunks of the plug remained stuck to the walls; however enough was cleared out to allow fluid flow. By moving the crawler back and forth and attacking with the front rim inflated or deflated, the angle of attack was changed. As a result all of the waste was cleared out of the way and the crawler was able to go through. The unplugging tests also revealed how well the waste would flow through the center of the crawler. The water pressure actually dissolved the plug and the dirty water would then flow out through the center of the crawler. The inner tube would actually form a watertight seal against the pipe wall such that the chamber formed in between the crawler and the plug would flood and the waste would only be able to escape through the center of the crawler. Whenever the front rim was released, a large amount 113 | P a g e of waste water would then flow backwards. This test further revealed just how effective the adhesion of the inner tubes is to the pipe walls. Not only were the inner tubes able to seal in the water, once they were released and wet with the dirty water, the crawler was still able to crawl through the slippery pipe walls. In fact, the crawler was able to crawl forth even when fully submerged. Figure 96: Crawler Approaching Nozzle Figure 97: Plug Breaking Under Water Pressure 114 | P a g e Figure 98: Plug Cleared Out 7.5 Evaluation of Experimental Results 7.5.1 Pulling Force The maximum pulling force is responsible for how far the crawler can travel in a pipeline. Table 13 shows the maximum force achieved by the prototype is 27.3 lbs. The prototype s tether consisted of three components: the air lines (3), the hydraulic line and the wench line. After weighing the three components separately and summing them the total weight of a 100ft prototype tether line was equal to 10.7 lbs. Furthermore, if the pulling force of the prototype (27.3 lbs) is divided by the weight of 100 ft of tether line (10.7 lbs) this equals 2.55. Multiplying 2.55 by 100 ft will equal the total length that the prototype can pull (neglecting friction effects) equaling 255 ft. The variation to the final crawler s tether will include two additional air lines. A 100ft tether will weigh approximately 15 lbs. Following similar procedure as above from Table 13 the theoretical force created by the final crawler will reach magnitudes of 345 lbs. A pulling force of 345 lbs will allow the crawler to travel 2300 feet (neglecting frictional forces). 115 | P a g e 7.5.2 Crawler Speed Figure 99: Compressed Length of 9 Inches Figure 100: Extended Length of 14 Inches 116 | P a g e The speed of the crawler is dependent upon two factors, the distance that it travels with every expansion and the speed at which it can expand or contract the rims and bellows. With the dimensions of the prototype, the difference between the collapsed and extended lengths is 5 inches. This means that regardless of how fast the crawler expands or contracts, it can only gain five inches per movement. The rates of expansion and contraction determine how quickly those five inches can be gained. This is dependent on the flow rates of air in and out of the various air cavities. Some leakages in the prototype crawler may have slowed it down somewhat. The speed of the crawler can be increased considerably by addressing concerns in both of these areas. A longer bellows can be used, or simply a bellows with a superior collapse ratio such that more distance is gained per movement. As far as flow rates, increasing the thickness of the lines somewhat and using a compressor and vacuum that can provide a higher cfm value can provide improvements in that area. The final crawler design incorporates these improvements, specifically by using a superior bellows which has a collapse ratio of 8:1, meaning that an eight inch bellow can collapse to 1 inch when compressed. This also means that the crawler can gain seven inches per motion if the bellows were 8 inches in length. 7.5.3 Unplugging Ability Some of the problems with the sewer nozzle may be attributed to the orifice size of the nozzle. The sewer nozzle used for testing on the crawler used the smallest available orifice size for this type of nozzle. However, this orifice is still rather large for the pressure washer which was used. With a larger washer, this nozzle could prove effective in future testing. However, a traditional nozzle with a smaller orifice and the same pressure washer machine proved to be effective enough. Besides the unplugging tool validation, this test was vital in learning about the movement characteristics of the waste water. There were some initial concerns as to whether the waste would flow through the center as desired. The 117 | P a g e test revealed that it would flow through the center satisfactorily. However, it was found that larger quantities of waste could flow around instead of through the crawler. One of the final crawler designs takes advantage of the way that water flows out around the crawler by using pistons to grab the pipe walls, thereby allowing the waste to flow out around the body. This means of grabbing the pipe walls would allow for the crawler to move forward and also stay in place without ever sealing the pipe walls. This also eliminates the center hole and as such the dual bellows can be replaced by a single bellow. 7.6 Improvement of the Design The most challenging task of the crawler is to travel through a 90 degree angled elbow. Individually, the original design rims were found to fit through the elbows quite well. However, with the crawler assembled, the bodies would wedge up against the elbow walls and become stuck. This was alleviated by modifying the rims in order to reduce the areas that tended to become wedged. The crawler bodies were shortened and reduced in diameter as compared to the original design to allow the bodies to pivot through the corner. The final prototype rims have thinner ends and their narrower bodies allow them to turn through the bends with more ease. 7.7 Discussion As the crawler approaches the 90 degree elbow the front body eases through, however, the rear has a bit more difficulty. This may be due to the way each body is pulled/pushed when inside the pipe. The front of the crawler is pushed through by positive pressure, equal to 20 psi. The rear body of the crawler is pulled through with negative pressure equal to 20 inHg or 9.82 psi. The difference in pressure is responsible for the rear of the crawler to make it through a 90 degree elbow. 118 | P a g e 8. Design Considerations 8.1 Assembly and Disassembly The bellow is attached by flanges located on its ends which allow it to be bolted directly to the front and rear bodies. The camera is mounted in the recess of the front body and its wires run between the walls of the double bellow. The pneumatic lines will feed the designated air cavities and hydraulic tool will mount firmly in position in the front of the crawler. The final assembly will be constructed in a similar manner to the prototype however assembly time will be drastically reduced. Custom c-clamps that are fastened by screws replace the time consuming process of the clamping procedure done on the prototype. 8.2 Maintenance of the System The crawler and its tether are designed for a one time unplugging use. However, regular maintenance is needed for components outside of pipeline. These include the required maintenance for air compressor vacuum, and hydraulic system. The pneumatic plumbing specifically the vacuum lines will need to be replaced as they will be contaminated with polluted air existing in the radioactive pipelines. 8.3 Environmental Impact The result of the crawler s unplugging capability has a very positive influence on the environment. The crawler will aid the United States Department of Energy to transport highly radioactive waste in a timely and efficient manner. The accelerated transport of radioactive waste from leaking single-shelled tanks will reduce the total amount of contaminated soil and ground water. The crawler and the process of crawling through a radioactive pipeline do pose some potential negative environment impacts that will be addressed. While the crawler is in a vacuum stage it is possible that it 119 | P a g e may pull contaminated air out into the atmosphere. An air filter used in the nuclear industry will be used to prevent contaminated air from expelling into the environment. The crawler and tether will be radioactive the instant it is introduced to the pipeline. To prevent the contamination of objects outside the pipeline, the crawler will be contained in a lead housing with a reeling system, see figure below. The crawler will be reeled in by a winch while the tether line is spooled alongside it. The crawler will be stored inside this unit and removed from the site safely. Figure 101: Crawler Housing 8.4 Risk Assessment When dealing with radioactive environments there is an obvious hazard to human life. Although components have been added to ensure the safety of crawler operation (air filters and the crawler housing), proper personal Protective Equipment (PPE) should be worn when operating crawler in radioactive environments. 120 | P a g e 9. Conclusion 9.1 Conclusion and Discussion The United States DOE is faced with the daunting task of high level waste transfer between two underground tanks. To prevent the further contamination of radioactive material into neighboring soil and ground water, including the Columbia River, the DOE must move millions of gallons into secure tanks by 2040. During the transfer process of nuclear waste, clogs/plugs have formed in the transfer pipelines and treatment facilities. Current technologies prove to be quite ineffective thus a new technology is needed to aid with the timely transfer of radioactive waste. There is a vast amount of crawlers that exist, most of which are for inspection purposes. The peristaltic crawler for the removal of radioactive plugs is different. It has an abrasive tool at the end to remove the plug. The crawler is able to navigate around 90 degree bends and up vertical pipe sections. The crawler has radiation hardened material that maintains integrity during the duration of unplugging. The final crawler is modeled to be able to apply enough force to carry the crawler and its tether 2300 ft; theoretically. The distance of 2300 ft was calculated by neglecting friction and therefore it is improbable that the crawler can crawl this distance. The actual distance the crawler can travel will be based on the frictional forces inside the pipeline and how the 90 degree elbows affect the force required to pull the tether. The crawler would be more feasible for the unplugging of pipes in treatment facilities, where pipelines don t stretch 7 miles, but are a few hundred feet. The crawler has a hydraulic abrasive tool attached to the front drastically simplifies the crawler s design in a radioactive environment. With no circuitry or actuators there is no concern for effects of radiation on circuits. Since the peristaltic is pneumatic by design it can work in an aqueous environment. Air vessels are air tight; therefore they are water tight as well. 121 | P a g e The locomotion of the crawler is suitable for pipeline applications that include vertical sections and 90 degree bends. The unplugging ability of the crawler is dependent on the type of unplugging tool used. 9.2 Commercialization Prospects of the Product Although the crawler was designed for the unplugging of radioactive plugs the design can be used in a wide variety of other areas. The simplicity of the design allows the crawler to be slim in size and has no major electronic components. With the abrasive tool removed it can become an inspection device. The crawler as an inspection robot will only need pneumatic controls. Depending on the crawler s alternative applications, materials will need to be selected based on the pipeline s nature. Unlike the expensive radiation hardened radioactive unplugging robot, the crawler will be less expensive to operate and maintain when in less hazardous environments. 9.3 Future Work Although the crawler is successful at maneuvering in a pipeline, further abrasive tools need to made for the successful removal of radioactive plugs. The successful removal of a plug is based on two things: tool effectiveness and a sufficient path for removed plug debris to travel to the back of the crawler. A hydraulic pressure nozzle was used in the project and as mentioned before may not be the most effective tool against certain types of plugs. Therefore future work will include the implementation of a mechanical type abrasive tool. The mechanical abrasive tool can be powered by hydraulics as to avoid the use of circuitry. Whether the abrasive tool is a pressure nozzle or a mechanical auger, the sizing of the tool is extremely limited by the dimensions of the pipe. The main obstacle is the 4.25 turning radius that limits the abrasive tools dimensions. Optimization of the abrasive tools size and power output will need to be studied to ensure the most efficient successful plug removal tool. 122 | P a g e In the process of plug removal, plug material that dislodge will be transported to the back of the crawler. The current design implements a double bellow to allow the waste to travel through the center of the bellow. However, the hydraulic line runs through the center of the crawler and restricts the area to which the debris can pass. Many other variations exist that may improve the movement of loose debris. If the inner tubes were replaced by four piston type parts, the clearance area will be increased and the debris will travel around the crawler instead of through the center. The figure below shows the new path for debris to travel through. Figure 102: Clearance of Future Crawler Idea With the use of the four-piston type mechanism mounted on the perimeter of the front rim, the nozzle will be able to adjust the aim of the trajectory of the nozzle plume. By using pneumatics the individual pistons can be adjusted to aim the crawler head left, right, up or down. 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Detailed Engineering Drawings of Final Crawler Bodies Note: All Dimensions in inches Front Rim (Final) Front Rim Side View 129 | P a g e Front Rim Front View 130 | P a g e Front Rim Rear View 131 | P a g e Front Rim Detailed View 132 | P a g e Rear Rim (Final) Rear Rim Side View 133 | P a g e Rear Rim Rear View 134 | P a g e Rear Rim Front View 135 | P a g e Rear Rim Detailed View 136 | P a g e Appendix B. Detailed Engineering Drawings of Prototype Crawler Bodies Front Rim (Prototype) Front Rim Side View 137 | P a g e Front Rim Front View 138 | P a g e Front Rim Rear View 139 | P a g e Front Rim Detailed View 140 | P a g e Rear Rim (Prototype) Rear Rim Side View 141 | P a g e Rear Rim Front View 142 | P a g e Rear Rim Rear View 143 | P a g e Rear Rim Detailed View 144 | P a g e Appendix C: US Department of Energy Material Evaluation Charts [31] 145 | P a g e 146 | P a g e Appendix D: Raw Design Calculations 147 | P a g e 148 | P a g e 149 | P a g e Appendix E: Catalogs 150 | P a g e 151 | P a g e 152 | P a g e 153 | P a g e ...
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