Pipelines are an integral part of our energy infrastructure, delivering fuel to homes and businesses across the country. To ensure the safety and reliability of pipelines, it is important to have a robust leak detection system in place. This article will discuss the best practices for selecting a pipeline leak detection system, including performance requirements, the selection of field instrumentation, and the use of remote terminal units (RTUs).
Performance Requirements
The selection of a pipeline leak detection system should be based on performance requirements. The following table outlines the performance measures required for each class of pipeline applications:
G Sweet gas (treated gas, i.e., sale gas with specification A-120 (Hydrogen Sulfide, grains/100 SCF (grains/100 CM))
GS Sour gas (gas concentration H2S >1% Hydrogen Sulfide)
L Sweet liquid (stabilized crude or treated condensate <300 ppm Hydrogen Sulfide) LS Sour liquid (untreated hydrocarbon) >300 PPM Hydrogen Sulfide
LV Volatile sweet liquids <300 ppm Hydrogen Sulfide) LVS Volatile sour liquids >300 ppm Hydrogen Sulfide)
Leak Detection Requirements for Pipelines
Pipelines are highly regulated, and the requirements for leak detection vary depending on the type of pipeline and its purpose. The US Department of Transportation has established a set of minimum performance standards for pipeline leak detection systems. These standards are divided into four classes, based on the amount of liquid the pipeline can carry and the frequency of leak occurrence.
Class Requirements for Pipeline Leak Detection
The following tables (9 through 12) state the minimum performance measure requirements for each corresponding class of pipeline applications:
Class 1:
Class 1 pipelines are designed to carry lower volumes of liquid and are expected to have a low frequency of leaks. The minimum performance requirement for Class 1 pipelines is to detect a leak of 0.25 gallons per hour.
Class 2:
Class 2 pipelines are designed to carry higher volumes of liquid and are expected to have a medium frequency of leaks. The minimum performance requirement for Class 2 pipelines is to detect a leak of 0.5 gallons per hour.
Class 3:
Class 3 pipelines are designed to carry higher volumes of liquid and are expected to have a high frequency of leaks. The minimum performance requirement for Class 3 pipelines is to detect a leak of 1 gallon per hour.
Class 4:
Class 4 pipelines are designed to carry higher volumes of liquid and are expected to have a very high frequency of leaks. The minimum performance requirement for Class 4 pipelines is to detect a leak of 5 gallons per hour.
Leak Monitoring Package-Software Engine
Leak monitoring software provides continuous operator alert and logging functions for pipelines, including real-time simulation capability for diagnostics. It also provides a history archive of actual leak detected and suspected or filtered events. The software should also provide a report to indicate leak details with the capability to print or display on the designated operator workstation. The system should announce the location of the leak within a time frame that does not exceed twice the Pipeline Leak Detection time specified in Table 2. The report should include topographical locations coordinates, etc.
Field Instrumentation Selection Criteria
The selection and installation of field instrumentation for pipeline leak detection should meet the reliability and robustness measures for the pipeline class. This includes conventional instruments such as pressure, temperature, and other instruments recommended by the leak detection system.
Remote Terminal Units (RTUs)
Field devices may be dedicated for the application or shared with a distributed control system (DCS) or supervisory control and data acquisition (SCADA). The selection of either approach will depend on the performance measures of the application. Additionally, the use of dedicated communication media and operator interface subsystems should be considered.
Conclusion
Pipeline leak detection systems are essential for ensuring the safety and reliability of pipelines. This article discussed the best practices for selecting a pipeline leak detection system, including performance requirements, the selection of field instrumentation, and the use of remote terminal units (RTUs). By following these best practices, pipeline operators can ensure the proper leak detection system is in place for their application.