A hydrostatic test involves filling a portion of the pipeline with water and using pumps to add additional water in order to pressure test the pipeline for a specified period of time. Hydrostatic testing is used to strength test new pipe at the completion of pipeline installation in the field prior to placing the line in service.
Hydrostatic testing is also used for integrity assurance after a line is in operation. The hydrostatic test establishes the pressure carrying capacity of a pipeline and identifies defects that might affect integrity during operation. Should a defect be discovered, Marathon Pipe Line LLC (MPL) would repair the pipeline and perform the test again.
The purpose of a hydrostatic test is to test the integrity of the pipeline under environmentally safe conditions and to ensure the safe operation of the pipeline, both of which benefits the pipeline company, the public, and the environment.