The objective of this project is to develop a centralized and automated acoustic monitoring system to detect leaks in, and infringements on, high-pressure natural gas pipelines. This system will detect the unique sound waves and vibrations that are generated when a pipeline break releases gas due to landslides, excavations, demolitions, or other sudden disturbances. The system will be designed to monitor background noise inside the pipe and identify any new frequencies that might signal a pipeline rupture or pipeline infringement.
West Virginia University (WVU) – overall project management and research products
Dominion Transmission, Inc. – sensor package design and use of pipeline for tests
Morgantown, West Virginia 26506
Due to the high pressures present in gas pipelines, any rupture or leak resulting from infringement by excavations, blasting, landslides, mine subsidence, or other significant events will produce a sudden high supersonic velocity discharge. Such a discharge also produces a large amplitude rarefaction wave, followed by supersonic jet acoustic noise at unique frequencies. The external jet noise is picked up at the pipe wall openings, transferred to the gas inside and transmitted in the form of longitudinal waves by the gas and transverse vibrations by the pipe wall. In addition, similar signals may be generated by third party infringements (strikes on the pipeline) and the resultant acoustic signature transferred to and carried along in the gas flow.
West Virginia University is developing a Portable Acoustic Monitoring Package (PAMP) to record and identify acoustic signals characteristic of both leaks and third party infringement damage, as well as a number of normal pipeline operations (pump noise, valve and flow metering noise, manual pipeline water and gas blow-off, etc). The system is easily connected to the pipeline by a 0.5 inch National Pipe Thread (NPT) stainless steel fitting and is capable of operating on 1000 psi pipelines with instrumentation designed to measure acoustic waves over the entire frequency range from zero to 16,000 Hz. Four instruments provide the necessary measurements: (1) microphone, (2) three-inch water full range differential pressure transducer with a 0.1 percent of range sensitivity, (3) a novel three -inch to 100-inch water range amplifier, and (4) a line-pressure transducer.
Development of online technology capable of identifying and locating natural gas leaks and infringements in real time will enhance the integrity, operational reliability, safety, and security of the pipeline system and minimize loss of natural gas.
The PAMP has proven to satisfy all the expected requirements. It is easy to carry and install in the field, and has met all safety requirements specified by Dominion Transmission Inc. engineers. The PAMP plumbing tree is very rugged, weatherproof, and fairly inexpensive to build. The laptop data acquisition system allows online data frequency analysis. The newly developed signal range amplifier has proven to be an essential tool, which allows recording over a greatly increased range of measurable pressure pulse amplitudes without loss in sensor sensitivity.
All work specified in the cooperative agreement has been conducted and the project has been successfully completed.