Pneumatic testing is a procedure that utilizes air pressure to test pipelines for leakage. This method not only identifies leaks but also cleans and dries the piping system, allowing the pipeline to go immediately back into service at the end of the test. The pneumatic testing procedure is used when other testing methods are not feasible; for example, when testing with water is prevented by freezing conditions.
While the test is in progress, all station personnel must be kept out of the testing area. Personnel who are involved in testing must stand behind a barrier to ensure their safety, and the testing area must be marked as a dangerous site. Heavy traffic areas and pedestrians must be given notice of impending testing. The section of pipeline being tested must be supervised at all times during the test. Leakage or rupture during testing can result in property damage or serious injury. All piping in the test section must be restrained prior to testing so that no movement occurs. Before testing begins, personnel must also ensure that all testing connections are installed and secure, pipeline end closures are stable, any backfill is in place and compact and heat fusion joints are cooled. Personnel involved in testing are required to wear protective equipment on eyes and ears.
The project engineer determines the maximum test pressure that will be used and pipeline that will be tested. Recommended test length is no longer than 400 feet. All openings that are not closed by valves are covered with a 150-pound blind flange or other selected cover. Plug all drains and vents not required for the test and open all sections not involved in testing to the atmosphere. The project manager determines the opening test pressure, which is typically 25 pounds per square inch (psi), held for a minimum of 10 minutes. Leaks detected during this phase of testing will cause testing to stop. Increase pressure by 25 psi increments for a minimum of five minutes each. When maximum pressure is reached, hold for 10 minutes. Reduce pressure to 100 psi and hold at this pressure for 24 hours. At this time, remove pressure, using caution around escaping steam, debris and noise.
Completing the Procedure
After testing is finished, complete one or both of the following forms according to facility protocol: Pressure/Leak Testing Sheet (EN-MPS-706a) or Pressure and Temperature Log (EN-MPS-706b). The project engineer determines the appropriate place to file the forms. The pipeline is ready for use immediately after testing is complete.