Implementation of specifications and testing standards for three precision valves

The valve is the control part of the fluid transportation system, which has the functions of cut-off, regulation, diversion, prevention of counterflow, stabilization, diversion or overflow The valves used in the fluid control system, from the simple stop valve of Zui to the various valves used in the extremely complex automatic control system, have many varieties and specifications (1) generally, the strength test shall not be carried out for the valve, but after repair, the strength test shall be carried out for the valve body and bonnet or the valve body and bonnet damaged by corrosion For safety valve, its constant pressure, reseating pressure and other tests shall conform to the specifications and relevant regulations (2) strength and sealing test shall be conducted for the valve installation Spot check 20% of low-pressure valves, 100% of unqualified ones; 100% of medium and high-pressure valves (3) during the test, the valve shall be installed in the direction easy for inspection (4) for valves with welded connection, if the blind plate pressure test fails, the conical seal or O-ring seal can be used for pressure test (5) during the hydraulic test, the valve air shall be removed as much as possible (6) during the test, the pressure shall be increased gradually, and it is not allowed to increase sharply and suddenly (7) the duration of strength test and sealing type test is generally 2-3min, and important and special valves shall last for 5min The test time of small diameter valve can be shorter, and that of large diameter valve can be longer During the test, if there is any doubt, the test time can be extended During the strength test, no sweat or leakage is allowed on the valve body and bonnet Generally, the sealing test is only conducted once for valves, and twice for safety valves, high-pressure valves, etc During the test, small amount of leakage is allowed for low-pressure and large-diameter unimportant valves and valves with allowable leakage according to regulations; because 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 subject to the sealing test of the closing part, but shall be subject to the strength test and the sealing test of the packing and gasket (9) during pressure test, the valve closing force is only allowed to be closed by one person's normal physical strength; it is not allowed to apply force by means of lever or other tools (except for torque wrench) When the diameter of hand wheel is greater than or equal to 320mm, two people are allowed to close together (10) for the valve with upper seal, the packing shall be taken out for sealing test After the upper seal is closed, check whether there is leakage When testing with gas, check with water in the stuffing box During the packing sealing test, the upper seal is not allowed to be in the tight position (11) for the valve with driving device, the sealing test shall be carried out by closing the valve with driving device For the manual driving device, the sealing test of the valve closed by the action shall also be carried out (12) for the bypass valve installed on the main valve after the strength test and sealing test, the strength and sealing test shall be carried out on the main valve; when the closing part of the main valve is opened, it shall also be opened accordingly (13) during the strength test of cast iron valve, tap the valve body and bonnet with a copper hammer to check for leakage (14) when the valve is tested, except that the sealing surface of the plug valve is allowed to be oiled as specified, other valves are not allowed to be oiled on the sealing surface for test (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 the deformation of 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, the accumulated water in the valve shall be removed in time and wiped clean, and the test records shall be made.