These materials expand under high pressures, a process known as ‘creep’. The flexible nature of these materials makes it difficult to determine whether pressure loss during a test is the result of water leakage or pipe expansion. Other factors such as temperature can also influence the amount of expansion, further complicating the test analysis process.
A Type II pressure test begins by bringing the pipeline up to system test pressure (STP) where it is left for a specified time-period based on the pipe’s ramp-up time. The pressure loss during the test period is recorded and then resolved through a series of algorithms.