Hydrostatic (High Pressure) Test
A hydrostatic test is a way in which valves can be tested for strength and leaks which involves filling the valves with liquid and pressurization of the vessel to the specified test pressure.
Low Pressure Seat Test
Some valve styles and seating styles will seal better at higher pressures and not so great at low pressures, and vice-verse. This specification ensures that the design is capable of sealing to the required extent at a wide range of pressures.