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Herna Trading (Dalian) Co., Ltd. > Technical Articles > Principle of Valve Pressure Test and Analysis of Related Precautions

technical article

Analysis of the principle of valve pressure test and related matters needing attention

Read: 111 Release time: 1/7/2020
(1) In general, the valve is not tested for strength, but the valve body and valve cover or the valve body and valve cover damaged by corrosion shall be tested for strength after repair. For the safety valve, its constant pressure and return seat pressure and other tests shall comply with its specifications and relevant regulations.
(2) The valve installation shall be tested for strength and tightness. The low-pressure valve should be spot-checked at 20%. If it fails, it should be checked at 100%. The medium- and high-pressure valves should be checked at 100%.
(3) During the test, the valve installation position should be in a direction easy to check.
(4) Valves in the form of welded connections can be tested with conical seals or O-ring seals when pressure testing with a stern plate is not possible.
(5) The valve air should be eliminated as much as possible during the hydraulic test.
(6) During the test, the pressure should be gradually increased, and sudden and sudden pressure increase is not allowed.
(7) The duration of the strength test and leak test is generally 2 to 3 minutes. Important and special valves should last 5 minutes. The test time for small diameter valves can be correspondingly shorter, and the test time for large diameter valves can be correspondingly longer. During the test, if in doubt, the test time can be extended. During the strength test, the valve body and valve cover are not allowed to sweat or leak. For the tightness test, the rotor pump valve is usually performed only once, and the safety valve and high pressure valve are required to be performed twice. During the test, a small amount of leakage is allowed for low-pressure, large-caliber unimportant valves and valves that are allowed to leak; due to the different requirements of general valves, power station valves, marine valves, and other valves, leakage requirements are different. Should be implemented in accordance with relevant regulations.
(8) Throttle valves are not to be tested for tightness of closing parts, but are to be tested for strength and tightness at packings and gaskets.
(9) In the pressure test, the valve closing force can only be closed by one person's normal physical strength; no force can be applied by means of a tool such as a lever (except for a torque wrench). When the diameter of the handwheel is greater than or equal to 320mm, the two are allowed to work together. shut down.
(10) For valves with upper seals, the packing shall be taken out for sealing tests. After the upper seals are closed, check for leakage. When using gas for the test, check the water in the stuffing box. For the tightness test of the packing, the upper seal is not allowed to be in the close position.
(11) For valves with a driving device, when the sealing is tested, the driving device shall be used to close the valve to perform a tightness test. For manual drive devices, a seal test shall also be performed to close the valve manually.
(12) The bypass valve installed on the main valve after the strength test and tightness test, the strength and tightness test is performed on the main valve; when the main valve closing part is opened, it should also be opened.
(13) During the strength test of cast iron valves, use a copper hammer to tap the valve body and bonnet to check for leakage.
(14) When testing the valve, except for the plug valve, the sealing surface is allowed to be oiled, other valves are not allowed to be oiled on the sealing surface.
(15) When the valve is tested for pressure, the pressing force of the blind plate on the valve should not be too large, so as not to deform the valve and affect the test result (if the cast iron valve is pressed too tightly, it will be damaged).
(16) After the pressure test of the valve is completed, the water accumulated in the valve should be eliminated and wiped clean, and the test records should be made.

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