Valve pressing precautions
The principle and matters needing attention of valve pressure test are as follows:
(1) in general, the valve does not do strength test, but repair after the body and valve cover or valve cover corrosion damage should be done strength test.For safety valve, its fixed pressure and back seat pressure and other tests shall be in accordance with the specification and the relevant regulations.
(2) the valve installation should be strength and sealing test.Low pressure valve spot check 20%, if unqualified should be 100% inspection;Medium and high pressure valves should be inspected 100%.
(3) during the test, the valve shall be installed in a direction that is easy to check.
(4) for the valve in the form of welding connection, tapered seal or o-ring seal can be used for pressure test when pressure test cannot be done with huang plate.
(5) hydraulic test will be the valve air as far as possible.
(6) the pressure should be increased gradually during the test, sharp and sudden pressurization is not allowed.
(7) the duration of strength test and sealing type test is generally 2~3MIN. Important and special valves should last for 5MIN.Small diameter valve test time can be relatively short, large diameter valve test time can be relatively long.During the test, if in doubt, the test time can be extended.During the strength test, the valve body and bonnet are not allowed to sweat or leak.Sealing test, the general valve can only be carried out once, the safety valve, high pressure valve and so on need to be carried out twice.During the test, minor leakage is allowed for low-pressure and large-diameter unimportant valves and those with regulations that allow leakage.Because of the general valve, power plant valve, Marine valve and other valve requirements vary, the leakage according to the relevant provisions.
(8) after the completion of pressure test of the valve, the water inside the valve should be removed in time and cleaned, and the pressure test record should be made.