Hydrostatic testing is a process used to inspect equipment such as fire extinguishing cylinders, storage tanks, gas cylinders and chemical pipelines, through use of a hydrostatic tester. The equipment is examined for leaks, and the overall integrity of the units are assessed. The hydrostatic tester measures the rate of expansion of the tube under water pressure, which ultimately determines whether the unit can safely hold the amount of pressure it is rated for.
Hydrostatic testing begins with filling a component with liquid, often water, until the pressure reaches a specified level. An amount of pressure greater than the designed working pressure of the equipment is applied and held for a set timeframe, during which the equipment is examined for leaks. By applying fluorescent dye or similar substance to the liquid, the inspection can be more easily performed and analyzed, if necessary.
Hydrostatic testing is often used to quality a piece of equipment that has been repaired or rebuilt, prior to it returning to service. It is commonly used for testing low pressure, stainless steel canisters that are required to be tested by the Department of Transportation (DOT). A hydrostatic test will indicate whether or not there are any leaks in the equipment at the time of the test, as a means of verifying whether it is safe to put back into service.