A test in which the soundness of tanks, closed containers or pressure vessels is determined by applying internal pressure. It may be nondestructive or destructive, as required. The pressure is applied hydrostatically, and in this method of testing there is little tendency for the container to disintegrate explosively in case of rupture and sudden release of pressure. The equipment required for hydrostatic testing consists of a pump, pressure gauge, and the pipe necessary to connect to the device being tested.
To conduct a hydrostatic test, the vessel to be tested is completely filled with water and all air bubbles are allowed to escape. After all outlets have been closed, the pump is operated until the desired pressure is obtained. Pressures up to 41 MPa (6000 psi) may be easily obtained.
In some instances specifications call for a hammer test of the pressure vessel while under twice the working pressure. In this case the weight of the hammer in pounds is equal to the shell thickness in tenths of an inch. Blows are struck at 15cm (6 in.) intervals at both sides of the weld for the full length of the seam. A thorough visual inspection follows; then the pressure is increased to three times the working pressure and the seam is again inspected. See TUBE TESTING.