The valve pressure test is to find out the bearing range of the valve, but we will inevitably cause harm during the pressure test of the valve. In order to reduce damage, we should also pay attention. Next, I will explain the principles of valve pressure testing and the matters we should pay attention to. Ensure your own safety as much as possible. The principles and precautions for valve pressure testing are as follows: (1) Under normal circumstances, the strength test is not required for the valve, but the strength test should be performed on the valve body and bonnet or the valve body and bonnet damaged by corrosion after repair. For the safety valve, its constant pressure, reseating pressure and other tests shall comply with the requirements of its manual and relevant regulations. (2) The strength and tightness test of the valve installation shall be carried out. 20% random inspection of low-pressure valves
, 100% inspection if unqualified; 100% inspection of medium and high pressure valves. (3) During the test, the valve installation position should be in the direction that can be easily checked. (4) For valves in the form of welded connections, if the pressure test with the slap plate fails, a conical seal or an O-ring seal can be used for pressure test. (5) The valve air should be excluded as much as possible during the hydraulic test. (6) During the test, the pressure should be gradually increased, and rapid and sudden pressure increase is not allowed. (7) The duration of strength test and tightness test is generally 2~3min, and important and special valves should last for 5min. The test time of small-diameter valves can be correspondingly shorter, and the test time of 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 valve cover are not allowed to sweat or leak. For the sealing test, the general valve is only carried out once, and the safety valve, high-pressure valve and other valves need to be carried out twice. During the test, a small amount of leakage is allowed for unimportant valves with low pressure and large diameter, as well as valves with regulations that allow leakage; due to the different requirements for general valves, power station valves, marine valves and other valves, the leakage requirements are different. It should be implemented in accordance with relevant regulations. (8) The tightness test of the closing parts is not required for the throttle valve, but the strength test and the tightness test of the packing and gasket shall be carried out. (9) During the pressure test, the closing force of the valve can only be closed by the normal physical strength of one person; it is not allowed to use tools such as levers (except torque wrenches) to add force. When the diameter of the handwheel is greater than or equal to 320mm, two people are allowed to work together. closure. (10) For valves with an upper seal, the packing should be taken out for a tightness test. After the upper seal is closed, check for leakage. When testing with gas, check with water in the stuffing box. When doing the packing tightness test, the upper seal is not allowed to be in the tight position. (11) For any valve with a driving device, when testing its tightness, the driving device shall be used to close the valve and conduct a tightness test. For manually actuated devices, a seal test for manually closed valves shall also be carried out. (12) For the bypass valve installed on the main valve after the strength test and the tightness test, the strength and tightness test of the main valve shall be carried out; when the main valve closing part is opened, it shall also be opened. (13) During the strength test of cast iron valves, tap the valve body and bonnet with a copper hammer to check for leakage. (14) When the valve is tested, except for the plug valve that allows the sealing surface to be oiled, other valves are not allowed to be oiled on the sealing surface. (15) When the valve is pressure tested, 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 effect (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 removed in time and wiped clean, and the test record should be made. The above is the content of the valve pressure test and our precautions. The reason for the valve pressure test is to use the valve more proficiently in the future, and the precautions are to find the most effective data for the valve pressure test while ensuring our safety, and get the results we want.
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