TWI Industrial Member Report Summary 599/1997
K Bell
On completion of manufacture, pressure vessels fabricated to codes must undergo a pressure test to demonstrate as far as possible, their structural integrity. For example, for BS 5500 the stress level during the hydrostatic pressure test must be at least 1.25 times the design stress of the vessel. For vessels designed to operate at below ambient temperatures the hydrostatic test is also a warm prestress or preload event, which has been shown to produce benefits in terms of the vessel's subsequent resistance to brittle fracture.