Recognizing the importance of leak detection, the U.S. Department of Transportation (DOT), Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS) has included leak detection provisions and considerations in several sections of 49 CFR parts 192 and 195.
The provisions include requirements for maintaining installed Computational Pipeline Monitoring (CPM) systems.
Section 195.134, CPM Leak Detection, applies to each hazardous liquid pipeline transporting liquid in single phase (without gas in the liquid). On such systems, each new computational pipeline monitoring (CPM) leak detection system and each replaced component of an existing CPM system must comply with section 4.2 of API 1130 in its design and with any other design criteria addressed in API 1130 for components of the
CPM leak detection system.
Section 195.444, CPM Leak Detection, requires each computational pipeline monitoring (CPM) leak detection system installed on a hazardous liquid pipeline transporting liquid in single phase (without gas in the liquid) to comply with API 1130 in operating, maintaining, testing, record keeping, and dispatcher training of the system.
In addition to regulations, PHMSA also issued an Advisory Bulletin, ADB-10-01, issued on January 26, 2010. The advisory bulletin goal was to advise and remind hazardous liquid pipeline operators of the importance of prompt and effective leak detection capability in protecting public safety and the environment.” The bulletin reminded operators of the importance of leak detection and their responsibilities to determine whether a computer-based leak detection system was appropriate for their pipeline.
The Pipeline Inspection, Protection, Enforcement, and Safety (PIPES) Act of 2006 explicitly drew attention to leak detection as part of an overall Integrity Management and Safety Program of a Pipeline. Under Sec. 21, PHMSA was required to produce a periodic leak detection technology study. The Leak Detection Study – DTPH56-11-D-000001 was released on December 10, 2012.
This study analyses past incidents to determine if additional LDS may have helped to reduce the consequences of the incident. The study reviews installed and currently available LDS technologies and examined existing LDS Standards to determine what gaps exist.
The study claims a recurring theme of false alarms. “The implication is that an LDS is expected to perform as an elementary industrial automation alarm, with an on/off state and six-sigma reliability. Any alarm that does not correspond to an actual leak is, with this thinking, an indicator of a failure of the LDS system.
The study finds that multiple technical studies confirm that far more thought is required in dealing with leak alarms, and the solution may be multiple redundant independent LDS, and training controllers to understand the physical principles causing the alarm in more detail. The study states that an LDS intended for rupture mitigation need not be very sensitive, but should be very fast.
The study also found that leak detection systems are engineered systems and that precisely the same technology, applied to two different pipelines, can have very different results.
The performance of a leak detection system depends critically on the quality of the engineering design, care with installation, continuing maintenance and periodic testing.
The study found that the emergence of “Hybrid” systems that incorporate more than one individual technology will improve leak detection.
The study confirms that selecting the correct leak detection for a pipeline depends on a variety of factors, including pipeline characteristics, product characteristics, instrumentation and communications capabilities, and economics. Pipeline systems vary widely in their physical characteristics and operational functions, and no one leak detection method is universally applicable or possesses all the features and functionality required for perfect leak detection performance. Perhaps worse, exactly the same leak detection method or system, applied to two different operating pipelines, will perform in different ways and with different measures of performance.
The study confirms that there is no technical reason why several different leak detection methods cannot be implemented at the same time. In fact, a basic engineering robustness principle calls for at least two methods that rely on entirely separate physical principles.
The study found that as leak detection is the first line of defense that triggers other impact mitigation, a leak detection system that prioritizes rapid detection and high sensitivity is particularly valuable. The study emphasizes that too many false alarms for standard operating practices can mask a leak by conditioning the operator over time to assume an alarm is false. This has been the case in too many real pipeline leaks. This can substantially degrade the mitigation value of leak detection, especially for larger leaks.
References
U.S. Department of Transportation, Pipeline and Hazardous Materials Safety Administration, Final Report No. 12-173, “Leak Detection Study – DTPH56-11-D-000001”, Dr. David Shaw, Dr.Martin Phillips, Ron Baker, Eduardo Munoz, Hamood Rehman, Carol Gibson, Christine Mayernik, December 10, 2012