Precautions for valves

(1) In general, the valve does not unde rgo strength test, but the repaired valve body and valve cover or the valve body and valve cover with corrosion damage shall unde rgo strength test. For safety valves, their constant pressure, return pressure and other tests shall conform to the specifications and relevant regulations. (2) The valve shall be tested for strength and tightness when installed properly. Low pressure valve spot check 20%, such as unqualified should be 100 % inspection; Medium and high pressure valves shall be 100 % inspected. (3) During the test, the valve installation position should be in the direction easy to check. (4) For valves in welded connection, cone seal or O-ring seal can be used for pressure test if the pressure test with blind plate is not feasible. (5) The valve air shall be excluded as far as possible during the hydraulic test. (6) During the test, the pressure shall gradually increase, and sharp and sudden pressurization is not allowed. (7) The duration of strength test and leak tightness test is generally 2 ~ 3 minutes, and important and special valves shall last 5 minutes. The test time for small diameter valves can be correspondingly shorter and that for large diameter valves can be correspondingly longer. During the test, the test time can be extended if there are any doubts. During the strength test, no sweat or leakage is allowed on the valve body and bonnet. For sealing test, the general valve of rotor pump shall be conducted only once, and the safety valve, high pressure valve and other essential valves shall be conducted twice. During the test, minor leakage is allowed for low-pressure and large-caliber unimportant valves and valves with regulations allowing leakage. As the requirements for general valves, power station valves, marine valves and other valves are different, the leakage requirements shall be implemented according to relevant regulations. (8) The throttle valve shall not be subjected to sealing test of the closing part, but shall be subjected to strength test and sealing test at the filler and gasket. (9) During the pressure test, the closing force of the valve only allows one person's normal physical strength to close; Do not use tools such as levers to apply force (except torque wrench). When the diameter of handwheel is larger than 320mm, both of them are allowed to close together. (10) The valve with upper seal shall take out the packing for sealing test. After the upper seal is closed, check for leakage. When testing with gas, fill the stuffing box with water for inspection. The upper seal is not allowed to be in a tight position during packing sealing test. (11) For valves with drive device, the drive device shall be applied to close the valve for sealing test when testing its sealing performance. For manual drive device, sealing test of manually closing valve shall also be conducted.