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Unformatted text preview: A COST EFFECTIVE ALTERNATIVE TO SYSTEM EXPANSION & PIPELINE MODIFICATION WITHOUT INTERRUPTING THE FLOW Presented by
Gunavel Rathinam Regional Sales Manager T.D.Williamson Asia Pacific Singapore May 10th 2007 INTRODUCTION The purpose of this paper is to provide applications information on the science of hot tapping and plugging with respect to plant piping in the petrochemical & process industry and introduce this cost effective methods for pipeline expansion and modification, while avoiding the costly and time-consuming conventional method which required the Asset owner / operator to depressurize the system, and in many cases, purge the product from the pipeline. The conventional method is known as Shutdown. Today, pipeline and piping systems are very complex and the associated facilities, such as compressors, pumps, and valves achieve optimal operation and longer life if pressure cycles are minimized. In addition, due to the critical demand for the product in the pipeline, the seller is often under contract to supply the product to the buyer without interruption in flow. In these cases, the pipeline owner / operator must seek a method to expand and / or modify their pipeline system without shutdown. This paper will focus on the most proven method to provide economic alternatives to shutdown, i.e.: • hot tapping, or hot tapping and line plugging with a bypass The material contained herein will provide the reader an understanding of the different applications in which hot tapping and plugging can be used while maintaining economy and efficiency of operation. In subsequent sections, the Concept of each option, as well as Examples of the various applications for both methods will be examined. DEFINITIONS Hot Tapping Hot tapping is simply the procedure for cutting an opening into a pipe which is carrying a product under pressure. A "hot tap" allows access to the inside of an operating pipeline without shutdown or spillage. A fitting is welded or mechanically attached to the line and a valve is attached to the fitting. A tapping machine is installed and the tap made through the valve. After the tap is made, the cutter is withdrawn and the valve closed. Hot / Wet / Cold Tapping (Shown: Standard Valve used when tapping to install lateral lines. SANDWICH® Valve Option allows temporary
plugging operation.) 1. A fitting is permanently secured to the line. 2. A permanent valve is installed on the fitting. 3. A TDW Tapping Machine is installed on the fitting, and the valve is opened. After pilot drill penetrates, the tapping machine fills with product, and air is purged from the housing. The tap is make through the line and the coupon is retained. 4. The valve is closed, and the tapping machine is removed. A branch connection is added, and the valve is opened. The new connection is ready to put into service. This field-proven TDW Procedure is quick and precise. Typical TDW Hot Tapping Procedure Materials, Applications and Standard Specifications Materials: Steel , cast/ductile iron, stainless steel, concrete, asbestos cement, plastic and others. Pipelines: Onshore, offshore, transmission, distribution, water/waste water, plant piping, refinery, chemical plants, steel mills, power plants, steam lines, buildings, cooling systems and others. Specs: Diameters - 1/2" through 102" Operating Pressures - Up to 2,200 psi Operating Temperatures - Up to 700° F. Typical Tapping Applications Size-On-Size Taps & Reduced Size Taps Size-On-Size Taps & Reduced Size Taps Angle Taps Welded Fittings Inverted Taps Mechanical Fittings Tank Taps Stopple Plugging After the tap is made, a STOPPLE Plugging Machine is installed on the valve and a plugging head inserted into the line. The plugging head, serving as a block valve, seals the line and retains pipeline pressure. If two plugging machines are used, or one plugging machine and an existing in-line valve, a section of pipe can be isolated and drained, making possible necessary repairs or modifications in the isolated section. A bypass can be installed around the isolated section, keeping the line in service. If a new section of line is being installed, it is possible to use the new section for a bypass while the old section is being removed. TDW Plugging and Completion Plug Systems 1. 2. Plugging Head Lowered. Plugging 3. 4. Seal is Attained. Product Temporarily Stopped Completion When all repairs have been made, the job is completed by installing a LOCK-O-RING Completion plug with scarfed nipple for piggable line, depending on pressure, in the fitting. The plugging head(s) is(are) removed, restoring service through the line. The tapping machine is then fitted with the completion plug, and it is inserted into, and locked into the fitting, providing a seal. The tapping machine, bypass and tapping valve are then removed, and a blind flange installed on the fitting. At a future date, in most cases, the blind flange can be removed, and the line re-entered, after removing the LOCK-O-RING Plug.
TDW STOPPLE® Procedure Options Double STOPPLE® Plugging Using a Spherical Tee Permanent Double STOPPLE® Plugging and Temporary Bypass Temporary Double STOPPLE® Plugging Spool Adapter and Temporary Bypass Temporary Materials, Applications and Standard Specifications Materials: Steel, cast/ductile iron, stainless steel, concrete, asbestos cement, plastic and others. Pipelines: Onshore, offshore, transmission, distribution, water/waste water, plant piping, refinery, chemical plants, steel mills, power plants, steam lines, buildings, cooling systems and others. Applications: New station tie-ins, repair or replacement of damaged lines or defective valves, relocation of lines and a variety of other needs. Specs: Diameters- 1/2" through 102" Operating Pressures - Up to 2,200 psi Operating Temperatures - Up to 700° F. Stopple Plugging / Stopping 1. The four fittings are permanently secured to the line. 2. Temporary SANDWICH® Valves are installed on the fittings, and taps are made through the valves. 3. Two STOPPLE® Plugging Machines are installed. Product is diverted through the temporary bypass. The isolated section is purged. Modifications are made to the isolated pipe section. The new section is purged and equalized, and the plugging heads are retracted. 4. The temporary bypass is removed. LOCK-O-RING® Plugs are installed in the STOPPLE® Fittings with a tapping machine. All equipment is then removed and blind flanges are installed on the fittings to complete the job. Versatility TDW manufactures fittings for 1-1/4" through 60" pipe. Fittings are designed to ANSI Class 150, 300, 400, or 600 specifications (SI PN 20, 50, 64, 100). Standard tapping machines are capable of tapping 1/2" to 102" holes, and are designed to pressures of 1,440 psi and to temperatures of 700 oF. Plugging Machines are capable of plugging 11/4” to 96” pipe in pressures to 1,000 psi and temperatures to 650 Deg F. Higher pressure tapping and plugging equipment can be provided for specific applications. TDW tapping machines and STOPPLE Plugging Machines have been used successfully in crude oil, fuel oil, gasoline, diesel oil, jet fuel, ethylene, butane, liquid propane gas, natural gas, carbon dioxide, flue gas, nitrogen, hydrogen, anhydrous ammonia, acids, steam, water and other products. STOPPLE Fittings A STOPPLE Fitting is a fitting which has been developed for a specific purpose. It is built not only to withstand the internal pressure of the pipeline, but also to take the forces developed by the STOPPLE Plugging Head which holds the line pressure. When the STOPPLE plugging operation is completed, the fitting remains on the pipeline and becomes an integral part of it. The design of the fitting is based on a combination of specifications for the design and construction of transport pipeline systems (for internal pressure) and of the results of many laboratory tests (for the measurement of the actual forces occurring during the STOPPLE plugging operation). These fittings are normally designed according to the rules specified in ASME B-31.41995 Liquid Petroleum Transportation Piping Systems, Chapter II, Part 2, Section 404-31, or in ASME B-31.8-1995 Gas Transmission and Distribution Piping Systems, Chapter III, Section 831.4 and Appendix R. These specifications generally deal with the calculation of the required reinforcement of welded branch connections. STOPPLE Fittings have been supplied according to the standards of such agencies as TUV, Stoomwezen, AIB, and Bureau de Mines, as well as to the requirements of individual customers like Shell DEP Specification, which widely used by various Gasline operators, specified fitting to be made to ANSI B31.4 , B31.8 or B31.3, where applicable. The fitting is provided with a special LOCK-O-RING Flange in which a LOCK-O-RING Plug can be installed. By this method, the tapping valves, as well as the other STOPPLE Plugging Equipment, can be recovered from the pipeline. STOPPLE Fittings are split longitudinally so that they can be installed on the pipeline. They are welded to the pipeline by two longitudinal welds and two circumferential welds so that the fittings become an integral pressure-tight part of the pipeline. First, the two longitudinal welds are completed, then, one of the circumferential welds. After the cooling of the first circumferential weld, the second circumferential weld is completed. The following conditions apply to a STOPPLE plugging job on a 24-inch gas transmission line. Similar procedures apply to gas, as well as other products. Selection of steel for the STOPPLE Fitting was very important because the fittings are welded to pipelines in service with gas flowing. This is extremely critical and must be controlled to assure dependable fillet welds between pipe and fitting. Several studies on hot-tap welding have been done in the past by British Gas, Distrigaz, Ruhrgas, and Gasunie. Transgas obtained approval of the Welding Institute of Bratislava, known for its advanced welding technology. Similar studies on hot-tap welding have been performed by a U.S. research organization sponsored by pipeline companies based in the U.S. and in other countries. All the studies have concluded hot-tap welding can be performed safely as long as the following conditions are met : 1. Pipeline conditions must be known in order to select the correct welding procedures. The product, velocity of the product, temperature of the product, and the atmospheric conditions at the job site all play an important role and can affect the quality of the weld connections. Knowledge of pipeline quality is critical. These factors include steel specification, carbon equivalent, external and internal corrosion, lamination in the pipe wall, and wall thickness. 2. 3. Fitting quality is a necessary ingredient in the weld process. These factors include steel specification, carbon equivalent, fitting-end preparation, defect-free weld bevels, and the gap between pipe OD and fitting internal diameter. Welding parameters must be determined. These include procedures, including type of electrodes and size, heat input (volts, ampere, speed of electrode, angle of electrode), preheat and welding sequence. Inspection before, during, and after installation of fitting is vital. 4. 5. Before : Magnetic particle, inspection of pipe at fitting location, ultrasonic inspection for possible internal corrosion, and verification of wall thickness. During : Ensure that weld procedures are maintained, including precautions for keeping electrodes dry (for hot-tap welding, T D. Williamson, Inc., advises the use of low-hydrogen electrodes). After : Magnetic particle inspection after the welds are completed. It is also recommended that welds be inspected 48 hours after they are completed to detect any possible delayed hydrogen cracking. Some companies are developing ultrasonic test procedures for inspection of the fillet welds. Several other areas of concern need to be taken into account during hot-tap welding, including heat-affected zone cracking, blow-through, and unstable pipeline contents. However, the most important concern may be cracks in the heat-affected zone of the fillet weld caused by hydrogen trapped in the weld metal during the rapid cooling process. Now, two small scarfed nipples (2”) are welded to the pipe. First, these are used to purge the pipe section after it has been isolated, and then they are used to equalize the pressure on both sides of the STOPPLE Plugging Heads before they are retracted from the pipeline. It is essential that all the fittings are welded on the pipeline such that the flange of the fitting is square to, and located on, the center of the pipeline. Some companies prefer a hydrostatic test of the welds; others, a pneumatic test with a pressure of 7 to 10 bars before hot tap is performed. With the latter method, the welds are soaped to indicate any leaks. Each company, of course, has its own specifications; the author recommends the pneumatic method. If the pressure in the pipeline is reasonably low, a safe pressure differential (during hydrostatic testing) should be determined in order to avoid pipe damage. This pressure differential depends on the pipe diameter, the wall thickness, and the length of the fitting. The pneumatic test can be done after installing the SANDWICH® Valve and the tapping machine on the fitting, the test being made through the "bleeder" valve on the machine. In this way, the flanged connections between the tapping machine, SANDWICH® Valve, and fitting, as well as the welds of the fitting, can be tested at one time. Tapping Under Pressure Tapping under pressure (or "hot-tapping") is simply the procedure for cutting an opening into a pipe which is carrying a product under pressure. The first step is to install the SANDWICH Valves/Isolation Valves on the STOPPLE and bypass fittings and to install 2" valves with full 2" bore on the purge-equalization nipples. A 2” size TOR Purge/ Equalisation Fitting are type of most commonly used in Stopple operation. A tapping machine is basically a long tube (the boring bar) inside a pipe (the frame). Inside the tube there is a feed screw which automatically extends the boring bar whenever the latter is rotating. Tapping machines can be driven by air or hydraulic motors, or operated by hand. The lower end of the boring bar is designed to accept a series of cutter sizes. For each size of the cutter, there is an adapter between the tapping machine and the valve. This adapter includes a flange which corresponds to that of the valve. After installing the proper cutter, pilot, and adapter, one is ready to begin the tap. The tapping machine is installed on the closed SANDWICH Valve. Installing with the valve closed ensures that there is sufficient clearance between the cutter/pilot assembly and the valve disc to close the valve after completing the tap. One must also take care that the machine is well centered in relation to the valve bore. The valve is opened and the cutter is lowered by hand until it touches the pipe. Beforehand, the total distance required to complete the tap should have been carefully determined and marked on the measuring rod of the tapping machine. The small bleeder valve on the tapping machine is opened and remains open. The machine is started and the boring bar begins feeding automatically. When the pilot drill has penetrated the pipe wall, the product fills the space inside the adapter, forcing out the air through the bleeder connection. When product starts coming out, all air has been purged, and the bleeder valve should be closed. The rpm of the tapping machine will depend upon the size of the cutter. Regardless of the cutter size, it is necessary that the speed at the cutter teeth ("tool speed") is the same. Each model of tapping machine has a preset feed rate, determined for optimal operation. The time required for the tap depends upon the diameter, the pipe material, etc. The coupon cut from the pipe is retained in the cutter by U-rods in the pilot drill. When the tap is completed, the cutter is retracted into the adapter, the SANDWICH Valve is closed, and the pressure above the valve is relieved. Whether the valve is well closed can be checked by means of the bleeder connection. Then, the tapping machine is dismounted from the SANDWICH Valve, and, after extracting the coupon from the cutter, the machine is ready for the next tap. It is usually more efficient to make the taps at the bypass fittings first so that the bypass line can be installed while the STOPPLE Plugging Machine taps are made. The small purge connections can be tapped after the drilling machine has been assembled and installed. STOPPLE Plugging Machine The STOPPLE Plugging Machine consists of three parts : 1. The hydraulic cylinder which powers the STOPPLE Plugging Head in and out of the pipe. 2. The plugging head and its sealing element. 3. The STOPPLE Housing. The STOPPLE Sealing Element, made from a fabric-reinforced rubber compound, is selected so that its outside diameter is conforms to the same size as the inside diameter of the pipeline, based on ultrasonic wall thickness scan. The plugging machines are installed on the SANDWICH Valves. Then, the valves on the bypass line are opened and the air in the bypass line is purged. Now the bypass is in operation. The SANDWICH Valves are opened and first the downstream plugging head is inserted. By proceeding in this manner, the liquid or gas stream can continue to flow smoothly through the bypass and not create a shock when the first plugging head is set. Now the upstream plugging head is inserted, and the entire stream is going through the bypass. The plugging operation, however, is not yet completed. One of the purge valves is opened and the pressure in the pipe section between the plugging heads is relieved, creating a pressure differential at each plugging head. The sealing element is designed so that this pressure differential will force its lip against the pipewall, thus making a complete seal. A good means of testing the completeness of the seal is by attaching a pressure gauge or a transparent hose (in case of liquid) to one of the purge valves and checking for a pressure buildup. The isolated pipe section can now be cut or repaired while the stream continues through the bypass line. After the repairs, etc., are completed and the new pipe section installed in the line, the pressure must be equalized on both sides of each STOPPLE Plugging Head. This can be done through the purge-equalization connection. When the pressure is equalized, the plugging head are retracted. The main pipeline is now back in operation. The bypass valves can be closed and the bypass line can be dismounted. The equalization valves can be closed and the connection from each to the STOPPLE Housing can be detached. The SANDWICH Valves are now closed and the plugging machines can be taken off. The STOPPLE plugging operation is completed and LOCK-O-RING Plugs and are installed in the special flanges of the fittings so that the SANDWICH Valves can be recovered. Installation of LOCK-O-RING Plugs LOCK-O-RING Plug installed in the LOCK-O-RING Flange forms a seal under the valve so that the latter may be taken off. The tapping machine which has been used to cut the pipe is now used to set the plug into the flange. The plug holder is attached to the end of the boring bar. When specified, LOCK-O-RING Plug are equipped at the factory to accept the coupon cut from the pipe. A LOCK-O-RING Plug with coupon, is attached and retracted into the adapter of the machine. The machine is now installed on the SANDWICH Valve and the valve is opened. The plug is lowered by hand until the groove in the LOCK-O-RING Plug is aligned with the segments of the retainer ring in the flange. Sealing is accomplished by the O-ring installed in a second groove in the plug. The retainer ring segments are extended, holding the plug in place and the tapping machine, and the SANDWICH Valve can now be removed. A blind flange is installed on the fitting, completing the operation. Examples of Hottap & Stopple operations as follows : 1. Record-Breaking 102" Tap T.D. Williamson, Inc., of Tulsa, Oklahoma, completed the largest recorded pipeline tap in Las Vegas, Nevada. The work was part of a large water system improvement project for Southern Nevada Water Authority to double the output of potable water to the fastest growing city in the United States, Las Vegas. Water from Lake Mead is currently drawn to the water treatment facility through a 120-inch steel-reinforced concrete water main. TDW Services was called in to make two taps into the concrete line through two 102-inch fittings. Each tap required approximately 18 hours to accomplish and were done with the line still in service. After completing each tap, the line was temporarily shut down, the tapping machine was removed, blind flanges were installed and the line was put back in service. The taps will permit a subsequent tie-in to a new 120-inch line, which will then feed the untreated water into a 180-inch steel line to the new water treatment plant that will operate alongside the existing plant. 2. Gulf Coast Refinery At a major Gulf Coast refinery, two expansion loops were to be installed in a 48” relief header that led to a flare stack 35 feet above the ground. An existing expansion joint packing gland had developed a leak and needed replacement. Extreme temperature changes caused great expansion and contraction in the pipe, so the decision was made to replace the single expansion joint with two expansion loops about 300 feet apart. The refinery wanted to keep its processing units in service. Shutting down that part of the operating system would have resulted in a significant loss in revenue. TDW Services was able to divert the flow, keeping the refinery up and running while the new expansion loops were installed. Our STOPPLE Plugging Machines remained in place for two weeks under the tough conditions associated with a flare line. The difficult project was completed successfully and shutdown of a major refinery was prevented. 3. TDW Services Taps at 1,000-foot Depth As offshore exploration for oil moves farther offshore, the exploration moves into deeper water, which necessitates deeper pipelines to pump the product ashore. T.D. Williamson, Inc., provides fittings for installation onto undersea pipelines and equipment for tapping through those fittings into the pipeline and stopping flow while necessary work is done. Striving to keep up with deeper and deeper drilling operations, TDW Services completed testing of equipment designed to make up to 16-inch taps in depths to 1,000 feet at 2,220 psi. Pipelines at that depth are constructed to withstand external water pressures of more than 450 psi. Divers working at these depths would require deep-sea diving equipment and a habitat around the work area. At deeper depths, where future work will be required, remotely operated vehicles (ROVs) will be required to perform installation work with the equipment operated remotely. Before TDW Services begins a subsea tapping operation, extensive planning and training take place. Since the equipment is often operated in near zero visibility, divers are trained in every aspect of equipment operation. They learn to operate the equipment by sense of touch while continually receiving instruction from a TDW technician on deck via voice communication. 4. Nuclear power facilities A nuclear power plant faced a challenge when it needed to replace eight 24” control valves in a “safety-related heat exchanger” unit. The control valves were located on a series of 24” carbon steel pipelines that branched off a common 48” header. There were no valves at the junction of the header and each branch. To keep the system in full operation, with a continuous flow of cooling water at approximately 100 psi, the power plant needed to install the valves without shutting down the 48” main line header. TDW Services technicians installed special tapping fittings on each 24” header, then they made hot taps through the fittings and into the lines. Next, they installed a Folding Head STOPPLE Plugging Machine. The folding head permitted the plugging head to enter the line through a smaller opening. The 48” main line header remained in service, feeding seven cells of the heat exchanger as, one by one, the eight 24” valves were replaced. The project was completed on time and within budget! TDW Services, Inc., has been serving the nuclear power industry since 1966. 5. Steam Valve Replaced In Nuclear Power Plant Steam is an essential component in the generation of electricity in any power plant. The loss of steam or a failure in a steam system can create serious operational problems, resulting in reduced production of electricity, or at the worst, a major shutdown. A midwestern nuclear power plant needed to replace a 2-inch control valve in a steam-return line. The valve, stuck in the open position, was discovered after the plant was brought back on line after a maintenance outage. After carefully considering capabilities and experience, the plant operator chose TDW Services, Inc., to isolate the faulty valve. In this case, a plugging fitting was welded and mechanical jackscrew actuator was used to insert the STOPPLE Plugging Head into the line against 250 pounds of pressure to stop flow, isolating the faulty valve. During the next eight hours, the valve was cut out and replaced. The portion of the steam system upstream from the plugging head remained in service while the valve was replaced. 6. 72” Stopple relocation job in Putrajaya, Malaysia To allow for new construction, the Federal Government Administrative Centre of Malaysia found it necessary to reroute two 6.6-kilometer segments of two 72”water mains running 22 kilometers between a reservoir and a water treatment plant outside Putrajaya, Malaysia. Both 72” lines were steel with internal concrete linings. Since the government agency wanted to avoid shutdown of this critical potable water supply, TDW Services, Inc. was contracted to perform the hot tapping and plugging operations. Four 48” hot taps were made in the two original 72” lines, and four 60” taps were accomplished on the new 72” permanent bypass lines. The 48” taps were completed in four hours each, while the 60” taps were finished in six hours each. TDW Services technicians installed double STOPPLE Plugging Machines with 48” x 72” folding heads on the 48” taps. This strategy saved money and time through the use of smaller fittings, shorter tapping times, and resulted in reduced weight on the line. The 48” folding heads were inserted through the 48” taps, then opened up to successfully plug the big 72”water mains. TDW effectively completed its part of this water development supply project without inconvenience to the local Malaysian residents and customers. Summary STOPPLE Plugging Machine operations, of course, are not always routine. Given enough time and technical information, however, practically any plugging operation can be accomplished. For example, in case fire hazard or safety regulations do not permit welding, there are specially designed fittings which do not require welding. For another example, if there is a main line valve conveniently located to the proposed STOPPLE Plugging Machine operation, it can be accomplished using only one set of STOPPLE plugging equipment STOPPLE Plugging Machines have been used successfully in pipelines containing natural gas, crude oil, propane, salt water, nitrogen, benzene, residue gas, fuel oil, ammonia, water, steam, and coke oven gas, with pressures from vacuum to 1,000 psi, to various depths under water, and to 700 Deg F. The Hot Tapping & Stopple plugging has many advantages : • Well proven technique • Solve maintenance problems at minimal cost with no shutdown or spillage • Different system for use both onshore and subsea • On stream repair without disruption of system & operation • Cost-effective method to perform repairing and pipe maintenance or line modification without shutting down your plant process • Done with very little drain down or refill • No loss of expensive process fluids With any application, safety is always the first consideration. T D. Williamson, Inc., has a complete line of equipment whereby all these operations can be accomplished safely. Continuing research and development is providing the equipment for handling new processes, higher pressures, larger pipe diameters, and the development of stronger pipe materials. While pipeline systems are continuously improved, developed, and repaired, pipeline maintenance is becoming more and more important, and under-pressure tapping and STOPPLE Plugging Machines are becoming standard maintenance equipment for most pipelines and process piping systems. Custom designs have been made to include sizes to 56 inches and pressures to 2,200 psi. ...
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This note was uploaded on 03/12/2010 for the course MECHANICAL M768501 taught by Professor Prof.han during the Spring '10 term at Institut Teknologi Bandung.
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