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Pipeline Leak Detection Operational Improvements [Pipeline & Gas Journal](Pipeline & Gas Journal Via Acquire Media NewsEdge) An Overview of Available Leak Detection Technologies (Editor's Note: This article is a summary of a full day training/seminar entitled "Understanding Pipeline Leak Detection Technologies - An Overview of Regulations. Standards, Requirements, Design & Operation." Dr. Shaw was scheduled to present and participate on two of the pipeline leak detection panels at the PHMSA "Improving Pipeline Leak Detection System Effectiveness and Understanding the Application of AutomatidRemote Control Valves " conference on March 27-28 in Washington, DC.) Introduction And References References include the U.S. Department of Transportation PHMSA Pipeline Leak Detection Technology Study Report to Congress as required by Section 21 of the Pipeline Inspection, Protection, Enforcement, and Safety (PIPES) Act of 2006, Public Law 109468 Supplemented by the PRCI current 2011 pending research report and US DOT PHMSA "Advance Notice of Proposed Rulemaking (ANPRM) closed in February 201 1 and formal comments/recommendations to the ANPRM by American Petroleum Institute (API) and Association of Oil Pipe Lines (AOPL). The energy transportation pipeline network of the United States consists of more than 2 million miles of pipelines. A dependable leak detection system (LDS) is important to promptly identify when a leak is occurring in order to shut down the line, isolate the leak, initiate response actions, reduce the volume of the spill, and mitigate safety, environmental, and economic consequences of the release. Recent Pipeline Leak Detection History In The U.S. Pipelines are historically a very safe means of transporting large quantities of oil, natural gas, fuels, and other hazardous materials. However, since 2002, there have been an average of two serious pipeline incidents per year and 1 23 significant pipeline incidents per year. By 2008 PHMSA completed inspections on all of the hazardous liquid pipeline operator's integrity programs. In response to the leak detection issues, PHMSA has initiated enforcement actions, or formally documented its concerns, for approximately 40% of hazardous liquid pipeline operators to date. Inspection Findings And Enforcement Actions Most hazardous liquid operators have some form of instrumented leak detection capability in place. However, PHMSA inspections identified a number of issues related to the operator's evaluation of its leak detection capabilities. Most issues fall into one of the following two categories: * The operator's IM procedures did not adequately require or specify that a leak detection evaluation be conducted. * The operator's IM procedures required that a leak detection evaluation be conducted, but the procedure or process by which the evaluation would be conducted was inadequate in some respect. In response to the enforcement actions, operators are required to submit revised procedures to correct inadequacies related to leak detection evaluations. Operators must then evaluate (or re-evaluate) their leak detection capabilities in accordance with these corrected procedures. Before a case is closed, PHMSA reviews the revised procedures and determines that the revisions satisfactorily address identified issues. The methods used for leak detection cover a wide spectrum of technologies and are based on a number of different detection principles. They vary from intermittent aerial inspections to hydrocarbon sensors to Supervisory Control and Data Acquisition (SCADA)-based, real-time monitoring. Each approach has its strengths and weaknesses. The operational principle, data and equipment requirements, strengths, weaknesses, and the realistic performance limits (size, response time, location, false alarm, etc.) for the leak detection methods listed above are addressed in this presentation. Leak detection systems are varied and uniquely designed for each pipeline application. However, for discussion purposes, leak detection technologies can be classified according to the physical principles involved in the leak detection. Using this type of classification, general categories of leak detection technologies can be divided into the following three groups: visual inspection/observation. instrumented monitoring of internal pipeline system conditions, and external instrumentation for detecting spilled hydrocarbons. Visual Inspection/Observation Simple visual observation is reliable and is part of every pipeline ROW patrolling and monitoring program, as mandated by Federal regulations. However, it cannot ensure timely detection of leaks. Instrumented Monitoring Of Internal Pipeline System Conditions The following list addresses the most commonly used approaches: 1 ) Regular or Periodic Monitoring of Operational Data a) Volume balance (over/short comparison) b) Rate of pressure/flow change c) Pressure point analysis d) Negative pressure wave method 2) Computational Pipeline Monitoring (CPM) a) Mass balance with line pack correction b) Real time transient modeling 3) Data Analysis Methods a) Statistical methods b) Digital signal analysis External Instrumentation For Detecting Spilled Hydrocarbons The following list addresses the most commonly used approaches: 1) Liquid Sensing Cables 2) Fiber Optic Cables 3) Vapor Sensing Tubes 4) Acoustic Emissions Key Considerations For Evaluating Adequacy Of Pipeline Leak Detection Systems Each leak detection system is unique based on the pipeline on which it is used. As such, the capabilities of the system and the degree to which it mitigates risk must be evaluated for each pipeline system. Pipeline size, length, operating parameters and instrumentation design will affect the detection time. Key considerations that should be taken into account include, but are not limited to, the following: (Note that much of the following discussion includes comments on the internal instrumented leak detection method, since it is by far the most widely used technology in the pipeline industry.) Rate of False Alarms and Misses Personnel Training and Qualification System Size and Complexity (Including Batch Line Factors) Leak Size or Leak Flow Rate Response Time Leak Location Estimation Release Volume Estimation Detecting Pre-Existing Leaks Detecting a Leak in Shut-in Pipeline Segments Detecting a Leak in Pipelines under a Slack Condition During Transients Sensitivity to Flow Conditions Multiphase Flow Robustness Availability Retrofit Feasibility Testing Cost Maintenance Integrity Management Program (IMP) Operators are required, by the IM rule, to have a means to detect leaks. Operators must also perform a critical, investigative, risk-based evaluation of their leak detection capabilities. The operator's evaluation of its leak detection capabilities must consider, at a minimum, the following factors: 1. Length and size of the pipeline 2. Type of product carried 3. The pipeline's proximity to the high consequence area 4. The swiftness of leak detection 5. Location of nearest response personnel 6. Leak history; and, 7. Risk assessment results. While the IM rule focuses on additional protections for HCAs, operators also have an obligation to detect and respond to leaks in non-HCAs. Typically, the same leak detection systems and procedures are used to detect leaks on both HCAs and non-HCAs on the same pipeline. Industry Confusion There are at least 80 External LDS vendors (DTS and Acoustic) in the U.S. There are at least 1 8 Computational Pipeline Monitoring (CPM) LDS by vendors in the U.S. There is a very real, and self-confessed, lack of know-how on LDS pipeline operators PHMSA: Operators' choices about methods of leak detection will be as varied as the types of pipeline construction, operation, and the environments in which they operate. Future And Conclusions PHMSA will soon propose additional measures designed to enhance the ability of control rooms and controllers to effectively detect and mitigate the consequences of a leak. A key component of the IM rule is continual improvement. Each operator's IM program is expected to mature and improve over time. LDS should always be selected to be fitfor-purpose. A major component of its cost is continuing training, maintenance, testing and improvement over time. Dual or more backup systems are preferred both for redundancy (no single point of failure) and also to extend the range of effectiveness of the LDS. It is better to have two cheaper LDS that work in synergy, than a single expensive, badly maintained LDS. Detailed engineering design of any LDS is needed to cover: 1) Suitability, sensitivity and requirements of CPM (API RP 1 130 for CPM for liquids); 2) Selection of instrumentation LDS (API 1149 for variable uncertainties and their effects on LDS); and 3) External Leak Detection Technology selection (Naval Facilities Engineering Service Center, UG-2028-ENV). Recommendations Pipeline owner/operators should conduct a comprehensive audit and leak detection system assessment at least once every two years. The audit and system assessment should consider additions and/or modifications to the pipeline network as these changes can severely impact system performance. The audit and system assessment should include a review of new technologies that could be used to enhance performance. The audit and system assessment should include a comprehensive cost/benefit anal- ysis. By Joe Summa and Dr. David Shaw Authors; Joseph Summa is president and CEO of Technical Toobaxes, Inc. in Houston. He studied chemical engineering at Lehigh University where he obtained his Bachelor of Science and later went on for master's degrees in chemical engineering and business. He served in the U.S. Air Force and began his commercial career in 1978 with Procter & Gamble (P&G). From 1985-95 he worked at Scientific Sqftware-Intercomp. Inc. (SSI) where many of the computational pipeline monitoring technologies for pipeline leak detection including but not limited to acoustic sensor technology, mass balance with line pack compensation, real-time transient model based technologies and others were developed and implemented for worldwide pipeline operators. In 1996 he was one of the founders of Technical Toolboxes (TT) a software and training company focused on integrated suites of technical software for the oil and gas industry with a focus on pipelines. He is active in several international not-for-profit research and new technology organizations including the Pipeline Research Council International (PRCI). He can be reached 713630-0505 ext. 203 [email protected]. Dr. David Show is the Managing Director of Technical Toolboxes Consulting LTD. He has more than 25 years of technical and managerial experience in the application of advanced technology and IT concepts to the energy industry worldwide. Following academic appointments in mathematical and engineering disciplines, he has held a wide variety of research, development, consulting, and senior project and executive management positions in the oil and gas and energy sectors. Recent experience involves executive and consulting assignments at major and national oil companies, and with international IT, automation and control suppliers. He holds a Ph.D. from Imperial College, is a past Chairman of Professional Education at the Society of Petroleum Engineers, and a past Royal Society Lecturer. He can be reached at dshaw@ttoolboxes. com. (c) 2012 Oildom Publishing Company of Texas, Inc. |