Valve Maintenance (NZ) 2017 Ltd (VMNZ) are IANZ accredited to carry out hydrostatic testing of all types of industrial valves up to a maximum of 700 barG in accordance with standard API 527.
In a hydrostatic test, the valve body is filled with testing fluid and the pressure is applied for a specified length of time. The valve is then inspected for any leakage. The testing fluid can be water, water with a corrosion inhibitor, or another liquid whose viscosity is not greater than that of water. The testing pressure depends on what material the valve is made of: steel, nickel-base alloy, cast iron, and so on. The test duration depends on the nominal valve size and valve class.
Three conditions can cause a valve to be rejected:
- There is visible leakage in the valve body assembly.
- There is leakage through static seals and gasketed joints (unless allowed by design).
- The hydrostatic test causes any distortion that impairs the valve operation.