nace-cp-interference-january-2008.pdf - CP Interference...

This preview shows page 1 out of 320 pages.

Unformatted text preview: CP Interference January 2008 ©NACE International, 2006 IMPORTANT NOTICE Neither the NACE International, its officers, directors, nor members thereof accept any responsibility for the use of the methods and materials discussed herein. No authorization is implied concerning the use of patented or copyrighted material. The information is advisory only and the use of the materials and methods is solely at the risk of the user. It is the responsibility of the each person to be aware of current local, state and federal regulations. This course is not intended to provide comprehensive coverage of regulations. Printed in the United States. All rights reserved. Reproduction of contents in whole or part or transfer into electronic or photographic storage without permission of copyright owner is expressly forbidden. Acknowledgements The scope, desired learning outcomes and performance criteria of this course were developed by the CP Task Group under the auspices of the NACE Education Administrative Committee. The time and expertise of several members of NACE International have gone into the development of this course—and its task analysis, course outline, student manual, classroom lab manual, presentation slides, and examinations. Their dedication and efforts are greatly appreciated. On behalf of NACE, we would like to thank the task group for its work. Their efforts were extraordinary and their goal was in the best interest of public service—to develop and provide a much needed training program that would help improve corrosion control efforts industry-wide. We also wish to thank their employers for being generously supportive of the substantial work and personal time that the members dedicated to this program. CP Interference Course Development Task Group Paul Nichols, Task Group Chairman Brian Holtsbaum Kevin Parker David A. Schramm Steven R. Zurbuchen Steven Nelson Donald R. Mayfield Shell Global Solutions, Houston, Texas CC Technologies Canada, Ltd., Calgary, Alberta CC Technologies, Mt. Pleasant, Michigan EN Engineering, Woodridge, Illinois EN Engineering, Topeka, Kansas Columbia Gas Transmission, Charleston, West Virginia Dominion Transmission, Delmont, Pennsylvania CP Interference Daily Course Outline DAY ONE Introduction, Welcome, Overview Chapter 1 Stray Current Interference DAY TWO Chapter 2 DC Interference (Includes Experiment 2-1) DAY THREE MORNING Chapter 2 DC Interference AFTERNOON Chapter 3 AC Interference (Includes experiments 3-1, 3-2, and 3-3) DAY FOUR Chapter 3 AC Interference DAY FIVE MORNING Chapter 3 AC Interference AFTERNOON Chapter 4 Telluric Current Interference DAY SIX MORNING Exam CP Interference Course Manual © NACE International, 2006 January 2007 Introduction Introduction The Cathodic Protection (CP) Interference course is a six-day course focusing on alternating current (AC) and direct current (DC) interference. The course includes in-depth coverage of both the theoretical concepts and the practical application of identifying interference and interference mitigation techniques. Students will learn to identify the causes and effects of interference as well as conduct tests to determine if an interference condition exists and perform calculations required to predict AC interference. The course is presented in a format of lecture, discussion and hands-on, in-class experiments, case studies and group exercises. There is a written examination at the conclusion of the course. Who Should Attend This course is designed for persons who have extensive CP field experience, a strong background in mathematics, and a strong technical background in CP. Prerequisites • CP 3–Cathodic Protection Technologist certification recommended • Minimum of 3 years CP work experience Length The course begins at 1 p.m. on Sunday and concludes Friday afternoon. Daily class hours: 8 a.m. to 6:30 p.m. Monday through Thursday and 8 a.m. to 3 p.m. Friday. Reference Book Students will receive the CP Interference Course Manual prior to the start of the course. A course manual on CD-ROM will be provided to students on-site. CP Interference Course Manual © NACE International, 2006 July 2007 1 Introduction Quizzes and Examinations There will be four (4) quizzes distributed during the week and reviewed in class by the instructors. This course has a written final examination. The final examinations will be given on Friday. The written final examination is open-book and students may bring reference materials and notes into the examination room. Non-communicating, battery-operated, silent, non-printing calculators, including calculators with alphanumeric keypads, are permitted for use during the examination. Calculating and computing devices having a QWERTY keypad arrangement similar to a typewriter or keyboard are not permitted. Such devices include but are not limited to palmtop, laptop, handheld, and desktop computers, calculators, databanks, data collectors, and organizers. Also excluded for use during the examination are communication devices such as pagers and cell phones along with cameras and recorders. A score of 70% or greater on the examination is required for successful completion of the course. All questions are from the concepts discussed in this training manual. You will receive written notification of your exam results as quickly as possible. Your results will not be available on Friday. Introductions We would like for each of you to stand, one at a time and introduce yourself to the class. Tell us: • Your name • Your company’s name and location • Your job function • Your experience related to CP Interference. CP Interference Course Manual © NACE International, 2006 July 2007 2 CP Interference Course Manual Table of Contents General Course Information Daily Course Outline Introduction Chapter 1–Stray Current Interference 1.1 Historical Background ........................................................... 1:1 1.2 Typical Stray Current Circuit Arising from a Transit System Operation ................................................................. 1:5 1.3 Stray Current Charge Transfer Reactions on a..................... Metallic Structure 1:6 1.4 Effects of Stray Current on Metallic Structures ..................... 1:9 1.4.1 1.4.2 1.4.3 At the Current Discharge Location...................................... At Area of Current Pick-Up ................................................. Along the Structure ............................................................. 1:9 1:15 1:19 1.5 Summary .............................................................................. 1:21 Summary of Equations.................................................................. 1:22 Figures Fig. 1-1 Fig. 1-2 Fig. 1-3 Fig. 1-4 Fig. 1-5 Fig. 1-6 Early Electric Trolley.............................................................. Pipe-to-soil Potential Changes due to Transit System Stray Current Activity were Recorded on Smoked Charts.. Co-efficient of Corrosion at Different Frequencies for Iron Electrode Denoted as Average Electrode Loss........... Typical Stray Current Paths Around a DC Transit System .... Typical Stray Current Interference on a Metallic Underground Structure ....................................................... Simplified pH Pourbaix Diagram For Iron in Water at 25ºC Showing Potential Shift Direction for Current Pick-up and Discharge at Low pH ................................................... CP Interference Course Manual © NACE International, 2006 June 2007 1:1 1:3 1:4 1:6 1:6 1:8 Fig. 1-7 Fig. 1-8 Fig. 1-9 Fig. 1-10 Fig. 1-11 Fig. 1-12 Fig. 1-13 Fig. 1-14 Fig. 1-15a Fig. 1-15b Fig. 1-16 Simplified pH Pourbaix Diagram For Iron in Water at 25ºC Showing Potential Shift Direction for Current Pick-up and Discharge at High pH................................................... Current Discharge from a Metal Structure to Earth via an Oxidation Reaction ........................................................ Superposition of a Stray Current and a Cathodic Protection Current at a Metal/Electrolyte Interface .............................. Randle’s Electrical Circuit Model of a Metal/Electrolyte Interface.............................................................................. Theoretical Conditions of Corrosion, Immunity and Passivation of (a) Aluminum at 25ºC and (b) Lead at 25ºC ................................................................. Comparison of Zn and Al Coatings for Corrosion Resistance as Functions of pH ........................................... Typical Section Through a Joint in Two Types of PCCP ....... Cathodic Blistering/Disbondment of Protective Coating ........ Stray Current Discharge and Pick-Up Around an Electrically Discontinuous Joint Though the Earth.............. Stray Current Discharge and Pick-Up Through the Internal Aqueous Medium Around an Electrically Discontinuous Bell and Spigot Joint on Cast Iron Piping.... Stray Current Circuit in an AC Electrical Distribution System................................................................................ 1:9 1:10 1:10 1:14 1:16 1:17 1:18 1:19 1:19 1:20 1:20 Tables Table 1-1 Theoretical Consumption Rates of Various Metals and Substances .................................................................. 1:12 Table 1-2 Electrochemical and Current Density Equivalence with Corrosion Rate.................................................................... 1:13 Chapter 2–DC Interference 2.1 Introduction ........................................................................... 2:1 2.2 Detecting Stray Current ........................................................ 2:23 2.2.1 Mitigation of Interference Effects from Impressed Current Cathodic Protection Systems ..................................... 2:24 a. Source Removal or Output Reduction .......................... 2:25 b. Installation of Isolating Fittings...................................... 2:26 c. Burying a Metallic Shield Next to the Interfered-with Structure .................................................................... 2:27 d. Installation of Galvanic Anodes on Interfered-with Structure at Point of Stray Current Discharge............ 2:28 e. Installation of an Impressed Current Distribution System on the Interfered-with Structure at Point of Stray Current Discharge................................................................... 2:33 f. i. Installing a Bond Between the Interfered-with and CP Interference Course Manual © NACE International, 2006 June 2007 Interfering Structures................................................ ii. Calculation of Bond Resistance ............................... g. Use of Coatings in the Mitigation of Interference Effects 2.2.2 2:33 2:35 2:40 Other Sources of DC Stray Current .................................... 2:41 a. DC Transit Systems ...................................................... 2:42 i. Analysis of Transit System Stray Currents ............... 2:44 ii. Mitigation of Transit System Stray Currents ............. 2:51 b. High Voltage Direct Current (HVDC) Electrical Transmission Systems ..................................................................... 2:55 c. DC Welding Operations ................................................ 2:57 Experiment 2-1: To Demonstrate DC Interference and Its Mitigation........................................................ 2:59 ………………………………………………………. ….. 2.64 Summary of Equations ............................................................................ 2:65 Case Study Figures Fig. 2-1 Fig. 2-2 Fig. 2-3 Fig. 2-4 Fig. 2-5 Fig. 2-6 Fig. 2-7a Fig. 2-7b Fig. 2-8 Fig. 2-9 Fig. 2-10 Fig. 2-11 Fig. 2-12 Fig. 2-13 Fig. 2-14 Fig. 2-15 Fig. 2-16 Parallel Current Paths in the Earth .................................... Parallel Current Paths in a Pipeline Cathodic Protection Section................................................................................ Parallel Current Paths in Vertically Stratified Soil Conditions Parallel Current Paths in Horizontally Stratified Soil Conditions........................................................................... Polarization Test Results....................................................... Stray Current in a Metallic Structure Parallel to a Cathodically Protected Structure ........................................ Voltage vs. Distance from a Vertically Oriented Anode ......... Multiple Vertical Anodes Connected to a Common Header Cable ..................................................................... Multiple Horizontal Anodes Connected to a Common Header Cable ..................................................................... Hemispherical Electrode........................................................ Cathodic Protection Circuit Model with Foreign Structure Intercepting the Anode Gradient......................................... Potential Profile along the Interfered-with Structure .............. Electrical Model for Interfered-with Pipe ................................ Attenuation Model.................................................................. Voltage Gradient in the Earth Around a Cathodically Protected Bare Pipeline ...................................................... Cathodic Protection Circuit Model ......................................... Cathodic Protection Circuit Model with Foreign Structure Intercepting the Anode Gradient......................................... Stray Current in a Foreign Metallic Structure that Intercepts both the Anodic and Cathodic Voltage Gradient................. CP Interference Course Manual © NACE International, 2006 June 2007 2:1 2:2 2:3 2:3 4:5 2:5 2:6 2:7 2:8 2:9 2:11 2:14 2:14 2:15 2:18 2:18 2:19 2:20 Fig. 2-17 Cathodic Protection Circuit Model with Foreign Structure Intercepting both Anodic and Cathodic Voltage Gradient... Fig. 2-18 Stray Current in a Foreign Metallic Structure that Intercepts the Cathodic Protection Gradient........................................ Fig. 2-19 Cathodic Protection Circuit Model for Foreign Structure Intercepting the Cathodic Voltage Gradient........................ Fig. 2:20 Typical Potential Profile on an Interfered-with Structure that Intersects both Anodic and Cathodic Voltage Gradient with the Current Source Interrupted..................... Fig. 2-21 Current Changes In and Near an Interfered-with Structure ... Fig. 2-22 Stray Current Arising from Installation of Isolating Fittings .... Fig. 2-23 Using a Buried Metallic Cable or Pipe as a Shield to Reduce Stray Current Interference..................................... Fig. 2-24 Cathodic Protection Current Model for a Buried Metallic Shield Connected to the Negative Terminal of the Transformer-Rectifier.......................................................... Fig. 2-25 Interference Mitigation using Galvanic Anodes at Stray Current Discharge Location ................................................ Fig. 2-26 Electrical Circuit Model for Mitigating Stray Current Interference at a Stray Current Discharge Site Using Galvanic Anodes................................................................. Fig. 2-27 Potential Profile Changes on a Pipeline where Stray Current is Discharging in an End-Wise Pattern .................. Fig. 2-28 Interference Mitigation Using a Resistance Bond.................. Fig. 2-29 Measurements Required to Determine Size of Resistance Bond Re .............................................................................. Fig. 2-30 Use of a Dielectric Coating to Mitigate Interference .............. Fig. 2-31 Typical Stray Current Paths Around a DC Transit System .... Fig. 2-32 Typical Structure-to-Soil Potential Recording with Time Caused by Interference from a DC Transit System ............ Fig. 2-33 Current Clamp Used to Measure Pipeline Currents .............. Fig. 2-34 Line Current Survey to Locate Source of Interference Using IR-Drop Test Stations ............................................... Fig. 2-35 Line Current Plots for Example in Figure 2-34 ...................... Fig. 2-36 Exposure Survey to Locate Point of Maximum Exposure...... Fig. 2-37 Exposure Survey Plots for Example in Figure 2-36 ............... Fig. 2-38 Mutual Survey to Confirm Source of Interference.................. Fig. 2-39 Pipe-to-Soil Potential Versus Pipe-to-Rail Potential for Example in Figure 2-38....................................................... Fig. 2-40 Exposure Survey Conducted Without the Measurement Of Pipeline Currents ........................................................... Fig. 2-41 Exposure Survey Plots for Example in Figure 2-40 ............... Fig. 2-42a Typical Embedded Track Installation..................................... Fig. 2-42b Typical Direct-Fixation Isolating Fastener ............................. Fig. 2-43 Typical Utilities Drainage System at a Transit Substation ..... Fig. 2-44 Schematic Showing Circulating Current between Transit Substations Through Direct Bonds to Utilities .................... Fig. 2-45 Forced Drainage Bonds Using a Potential Controlled Rectifier............................................................................... Fig. 2-46 Electrical Schematic for a HVDC System .............................. CP Interference Course Manual © NACE International, 2006 June 2007 2:20 2:21 2:22 2:23 2:24 2:26 2:27 2:28 2:29 2:30 2:33 2:34 2:36 2:41 2:42 2:43 2:44 2:45 2:46 2:47 2:48 2:48 2:49 2:50 2:50 2:52 2:52 2:52 2:53 2:54 2:55 Fig. 2-47 Potential-Time Plot for a Metallic Structure being Interfered-with by a HVDC System..................................... Fig. 2-48 Stray Current Caused by DC Welding Operations ................ 2:57 2:58 Experiment Schematic No. 1................................................................... Experiment Schematic No. 2................................................................... Experiment Schematic No. 3................................................................... 2:59 2:60 2:61 Table 2-1 Specific Leakage Resistances and Conductances in 1000 Ω-cm Soil or Water ....................................................... Table 2-2 Types of Reverse Current Switches ...................................... 2:13 2:54 Tables Chapter 3–AC Interference 3.1 Introduction ........................................................................... 3.1.1 3.1.2 3.1.3 Experiment 3-1: 3:1 Electrostatic (Capacitive) Coupling..................................... 3:2 Electromagnetic (Inductive) Coupling ................................. 3:11 Conductive Coupling (Resistive Coupling) During Powerline Fault Conditions........................................................................... 3:14 To Demonstrate the Effects of Electrostatic Induction ............................................................................. 3:16 3.2 Basic Theory of Electromagnetically Induced Voltages ........ 3:19 3.2.1 3.2.2 Experiment 3-2: AC Circuit Theory ............................................................... The Nature of Induced AC Pipeline Voltages ..................... 3:19 3:34 To Demonstrate the Effects of Electromagnetic Induction ............................................................................. 3:42 3.3 Induced AC Voltages ............................................................ 3:44 3.3.1 3.3.2 Experiment 3-3: Factors that Affect the Longitudinal Electric Field............... Factors that Affect the Pipeline Voltages............................ 3:44 3:48 To Further Investigate the Effects of Electromagnetic Induction ............................................................................. 3:57 3.4 Deleterious Effects of AC Interference.................................. 3:60 3.4.1 3.4.2 3.4.3 Electric Shock Hazards....................................................... AC Corrosion ...................................................................... .1 Theory........................................................................... .2 AC Corrosion Case Histories........................................ .3 AC Corrosion Field Test Proc...
View Full Document

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture