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Principles and precautions of valve pressure test

  • Categories:Industry news
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  • Time of issue:2019-12-23 09:46
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Principles and precautions of valve pressure test

(Summary description) In general, the valve is not tested for strength, but the repaired valve body and bonnet or corrosion-damaged valve body and bonnet should be tested for strength. For the safety valve, its constant pressure and reseating pressure and other tests shall comply with the specifications of its instructions and relevant regulations.

  • Categories:Industry news
  • Author:
  • Origin:
  • Time of issue:2019-12-23 09:46
  • Views:0

(1) In general, the valve is not tested for strength, but the repaired valve body and bonnet or corrosion-damaged valve body and bonnet should be tested for strength. For the safety valve, its constant pressure and reseating pressure and other tests shall comply with the specifications of its instructions and relevant regulations.

(2) The installation of the valve shall be tested for strength and tightness. Spot check of low pressure valves is 20%, if it fails, it should be 100% checked; medium and high pressure valves should be 100% checked.

(3) During the test, the installation position of the valve should be in the direction where it is easy to check.

(4) For valves with welded connection, if the pressure test is not possible with the slab plate, a cone seal or O-ring seal can be used for pressure test.

(5) During the hydraulic test, remove the valve air as much as possible.

(6) The pressure should be gradually increased during the test, and it is not allowed to increase pressure suddenly and suddenly.

(7) The duration of strength test and leak test is generally 2 ~ 3min, and important and special valves should last 5min. 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, the test time can be extended if in doubt. During the strength test, the valve body and bonnet are not allowed to sweat or leak. For the tightness test, the general valve is only performed once, and the safety valve, high-pressure valve, etc. are required to be performed twice. During the test, a small amount of leakage is allowed for low-pressure, large-diameter unimportant valves and valves with specified allowable leakage; due to the different requirements for general valves, power station valves, marine valves and other valves, the requirements for leakage Should be implemented in accordance with relevant regulations.

(8) Throttle valves are not tested for the tightness of the closing parts, but they should be tested for strength and the tightness at the packing and gasket.

(9) During the pressure test, the closing force of the valve is only allowed to be closed by one person's normal physical strength; it is not allowed to use force such as a lever (except for torque wrench). When the diameter of the hand wheel is greater than 320mm, two people are allowed shut down.

(10) For valves with an upper seal, the packing should be taken out for the tightness test. After the upper seal is closed, check for leakage. When using gas as a test, check with water in the stuffing box. When performing the packing tightness test, the upper seal is not allowed to be in a dense position.

(11) For valves with actuation device, when testing the tightness, the actuation device should be used to close the valve to conduct the tightness test. For manual drive devices, a sealing test for closing the valve by force shall also be carried out.

(12) After the strength test and the tightness test, the bypass valve installed on the main valve is tested for strength and tightness at 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, tap the valve body and bonnet with a brass hammer to check for leaks.

(14) When the valve is tested, except for the plug valve that allows oiling of the sealing surface, other valves are not allowed to be oiled on the sealing surface.

(15) During the pressure test of the valve, the pressing force of the blind plate on the valve should not be too large, so as to avoid deformation of the valve and affect the test effect (if the pressure of the cast iron valve is too tight, it will be damaged).

(16) After the pressure test of the valve is completed, the accumulated water in the valve should be removed and wiped off in time, and the test record should also be made.

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