What is Hydrostatic Testing and its Work Principle ?

Work principle

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.

Hydrostatic test requirements:

During the hydrostatic test, the water pressure should rise or fall slowly. When the working pressure is reached, the pressure boost should be suspended to check whether there is leakage or abnormal phenomenon, and then the pressure rise to the test pressure. The pressure remained constant during the inspection. Hydrostatic test should be carried out when the ambient temperature is higher than 5℃, otherwise there must be anti-freezing measures, to choose clean water, when the requirements are not high, industrial water can be used to replace clean water, water temperature should be higher than the surrounding dew point to prevent condensation on the surface of the boiler, but should not be too high, generally 20~70℃.

The test usually adopts the stepped-up method to check the deformation and leakage of the equipment while testing, and maintain the pressure for a certain time after the test pressure. There is no water drop or mist on the metal wall and weld seam of the pressure element. When the pressure is reduced to work pressure, there is no beads of water at the expansion mouth, After hydrostatic test, no residual deformation was found.

1. Pre-test phase:

(1) Raise the water pressure inside the pipe to the specified test pressure and stabilize the pressure for 30min. During the period, if the pressure drops, fill the pipe with water and the fill pressure shall not be higher than the test pressure;

(2) Check whether there is water leakage or damage in pipe joints, fittings and other places;

(3) In case of water leakage or damage, the pressure test shall be stopped in time, and the cause shall be found out and corresponding measures shall be taken before the pressure test is repeated.

2. Main test phrase:

stop filling pressure by water injection and stabilize it for 15min. When the pressure drop after 15min does not exceed the allowable pressure drop value, reduce the test pressure to the working pressure and keep the constant pressure for 30min, inspect appearance, If there is no water leakage, the hydrostatic test on this pipe is qualified.

Applicationns

Hydrostatic test is widely used in daily life, hydraulic flaw detection, pressure and blasting test of small valves, pressure vessels, all kinds of metal and non-metal pipe, testing hydraulic strength and sealing performance of various petroleum tools, pressure detection and revision of pressure instruments,fire hose and fire extinguisher and other fire equipment pressure and blasting test.