[ Valve Industry Network ] Valve is a control component in the fluid delivery system, with functions such as cut-off, regulation, diversion, anti-backflow, voltage regulation, shunt or overflow relief. A control valve for a fluid system, from the most simple shut-off valve to a variety of extremely complex used in the automatic control system valve that quite many varieties and specifications.

　　(1) Under normal circumstances, the valve is not tested for strength, but the valve body and bonnet of the valve body and bonnet or corrosion damage shall be tested for strength after repair. For safety valves , the constant pressure and return pressure and other tests shall comply with the specifications and relevant regulations.

　　(2) The valve installation shall be tested for strength and tightness. Low-pressure valves are checked 20%. If they are not qualified, 100% inspection should be carried out; medium and high-pressure valves should be checked 100%.

　　(3) When testing, the valve installation position should be in the direction of easy inspection.

　　(4) Valves in the form of welded joints, when the test is not possible with the slab, the taper seal or the O-ring seal can be used for the test pressure.

　　(5) The valve air should be excluded as much as possible during the hydraulic test.

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

　　(7) The strength test and the seal test duration are generally 2~3min, and the important and special valves should last for 5min. The test time of the small-diameter valve can be correspondingly shorter, and the test time of the large-diameter valve can be correspondingly longer. During the test, the test time can be extended if in doubt. During the strength test, the body and bonnet are not allowed to sweat or leak. For the sealing test, the valve is generally only used once, and the safety valve, high pressure valve and other raw valves need to be carried out twice. During the test, a small amount of leakage is allowed for low-pressure, large-diameter unimportant valves and valves that are allowed to allow leakage; since general-purpose valves, power station valves, marine valves, and other valves have different requirements, leakage requirements are required. It should be implemented in accordance with relevant regulations.

　　(8) The throttle valve shall not be used for the sealing test of the closing member, but shall be used for strength test and sealing test at the packing and gasket.

　　(9) During the pressure test, the valve closing force only allows one person's normal physical strength to close; it must not be applied by means of a lever or the like (except the torque wrench). When the diameter of the hand wheel is greater than 320 mm, the two are allowed to work together. shut down.

　　(10) For valves with upper seal, the packing should be taken out for sealing test. After sealing the upper part, check for leaks. When testing with gas, check the water in the stuffing box. When using the packing tightness test, the upper seal is not allowed to be in a tight position.

　　(11) Where a valve with a drive device is tested for its tightness, the drive device is used to close the valve to perform a tightness test. For manual drives, a seal test using a closed valve should also be performed.

　　(12) After the strength test and the seal test, the bypass valve installed on the main valve shall be tested for strength and tightness in the main valve; when the main valve closing member is opened, it shall also be opened.

　　(13) When testing the strength of cast iron valves, tap the valve body and bonnet with a copper hammer to check for leaks.

　　(14) When the valve is tested, except that the plug valve has provisions to allow the sealing surface to be oiled, other valves are not allowed to apply oil test on the sealing surface.

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

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