Hydrostatic and Performance Tests

Finding Leaks And Verifying Durability

Hydrostatic (Hydro) Testing also known as a Leak Test, which provides a method for finding leaks or verifying performance and durability in pressure vessels. The hydrostatic test is classified as a nondestructive testing techniques, meaning the sample is typically not harmed during the test. Hydro Testing is commonly used to test the strength and leakages  of piping systems, gas cylinders and boilers.

Hydrostatic testing is a type of pressure test that works by completely filling the component with water, removing the air contained within the unit, and pressurizing the system up to 1.5 times the design pressure limit the of the unit. The pressure is then held for a specific amount of time to visually inspect the system for leaks. Visual inspection can be enhanced by applying either tracer or fluorescent dyes to the liquid to determine where cracks and leaks are originating.

Standard hydrostatic testing procedures entail filling the test vessel with liquid, bleeding out air and then pressurizing the piece. The NDE inspector thoroughly examines the vessel for leaks or permanent changes in shape. The hydro test is performed with a nearly incompressible (compressible only by weight, not air pressure) liquid, usually water or oil, because it will only expand by a very small amount should the test piece fail and not pose a danger to the technician. The hydrostatic pressure test can also be performed with pressurized air, but this leak test is generally carried out with the vessel under water for safety reasons.

The pressure used in hydrostatic pressure testing is always considerably more than the operating pressure to give the customer a margin for safety. Typically the test is performed at 150 percent of the design or working pressure. For example, if a pipe was rated to a working pressure of 2000 PSI, it would be tested at 3000 PSI to ensure reliability. A sample that does not meet performance or durability specifications may fail and become unusable during the leak test.

AQSS has trained inspectors to independently observe the hydro test and to make sure that the test vessel does not have any leaks and will perform as per the design specifications.