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A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks.
Hydrotesting of pipes and/or pipelines are performed to expose defective materials that have missed previous detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system.
Buried high pressure oil and gas pipelines are tested for strength by pressurizing them to at least 125% of their maximum operating pressure (MAOP) at any point along their length. Since many long distance transmission pipelines are designed to have a steel hoop stress of 80% of specified minimum yield (SMYS) at MAOP, this means that the steel is stressed to SMYS and above during the testing, and test sections must be selected to ensure that excessive plastic deformation does not occur.
Leak testing is performed by matching changes in the measured pressure in the test section against the theoretical pressure changes calculated from changes in the measured temperature of the test section.
Noteworthy papers in OnePetro
Kawahara, Y., Umehara, Y., Iizuka, H., & Kikuchi, K. 2006. Development of Sea Water Hydrostatic Test System for LNG Storage Tank on the Ground. NACE International. OnePetro
Powell, D. E., Melancon, B., & Winters, R. H. 2011. Guidelines When Conducting Hydrostatic Pressure Tests And Management of Extended Dwell Times Through Dry/Wet Lay-Ups. NACE International. OnePetro
Texter, H. G. 1951. Internal Hydrostatic Pressure Testing as a Measure of the Performance Values of Oil Well Casing and Tubing. World Petroleum Congress. OnePetro