Under normal circumstances, industrial
VALVES are not used for strength tests when they are used, but the valve body and valve cover of the valve body and bonnet or corrosion damage should be tested for strength after repair. For safety valves, their constant pressure and seatback pressure and other tests shall comply with the specifications of their instructions and related procedures. The valve strength test and valve sealing test should be performed on the valve hydraulic test bench prior to valve installation. Low-pressure valve checks 20%, if unqualified should be 100% inspection; medium and high pressure valves should be 100% inspection. Valve pressure test commonly used media are water, oil, air, steam, nitrogen, etc., all kinds of industrial valves with pneumatic valve pressure test method is as follows:
1. Check valve and throttle valve pressure test method
For the strength test of the shutoff valve and the throttle valve, the assembled valve is usually placed in the pressure test frame, the valve flap is opened, the medium is injected to the specified value, and the valve body and the valve cover are checked for sweating and leakage. It is also possible to carry out strength tests in one piece. Sealing test only as a stop valve. During the test, the valve stem of the stop valve is in a vertical state, the valve flap is opened, the medium is introduced from the bottom end of the valve flap to the specified value, and the filler and the gasket are inspected; after the passage, the valve disc is closed, and the other end is opened to check for leakage. If the valve strength and sealability tests are to be done, the strength test can be done first, then depressurized to the sealability test value, check the packing and gasket; then close the valve flap, open the outlet end and check the sealing surface for leakage ( Shanghai Yonglong Valve Factory's J41B-40C liquid ammonia shut-off valve is also tested for pressure seals.)
2, the valve pressure test method
The strength test of the gate valve is the same as the shut-off valve. There are two methods for sealing the valve.
1 The gate is opened, so that the pressure in the valve rises to the specified value; then, the gate is closed, the gate valve is immediately taken out, and the leakage at the seals on both sides of the gate is checked or the test medium is directly injected into the plug on the valve cap to the specified value. Check the seals on both sides of the gate. The above method is called intermediate pressure test. This method is not suitable for sealing tests on gate valves with a nominal diameter of DN32mm or less.
2 Another method is to open the gate, so that the valve test pressure rises to the specified value; then close the gate, open the end of the blind, check the sealing surface leakage. And then down, make the above repeated test until qualified.
Pneumatic gate valve packing and gasket seal test shall be conducted before the gate seal test.
3, ball valve test method
The strength test of the pneumatic ball valve shall be performed with the ball valve sphere half opened.
1Floating ball valve sealing test: The valve is in a half-open state, one end is introduced into the test medium and the other end is closed; the ball is rotated several times, the closed state is opened when the valve is closed, and the sealing performance at the packing and the gasket is checked at the same time. There must be no leakage. The test medium is then introduced from the other end and the above test is repeated.
2 Fixed ball valve tightness test: Before the test, the ball is rotated several times without load, the fixed ball valve is in the closed state, the test medium is introduced from one end to the specified value, and the sealing performance of the introduction end is checked with a pressure gauge, and the accuracy of the pressure gauge is used. .5 to 1, the range is 1.6 times the test pressure. Within the prescribed time, no depressurization is acceptable; the test medium is then introduced from the other end and the above test is repeated. Then, the valve is in a half-open state, both ends are closed, the inner cavity is filled with the medium, and the filler and the gasket are checked under the test pressure without leakage.
3 The three-way ball valve shall be tested for hermeticity at various locations.
4, pressure test method of plug valve
When a plug valve was used for the strength test, the medium was introduced from one end, and the remaining passages were closed. The plug was rotated to the fully open working positions in sequence to test. The valve body was found to be acceptable.
2 In the sealing test, the through-flow cocks should keep the pressure in the chamber equal to the passage, rotate the stopper to the closed position, check from the other end, and then repeat the above test by rotating the stopper 180°; three-way or four-way stopcock. The pressure in the chamber and the end of the passage should be kept equal, and the stoppers are rotated to the closed position in turn, the pressure is introduced from the right-angle end, and the inspection is performed from the other end at the same time.
A non-acidic, dilute lubricating oil is allowed to be applied to the sealing surface before the plug valve test stand. No leaks and enlarged water droplets are found to be acceptable within the specified time. The plug valve test time can be shorter, generally regulated by the nominal diameter of l ~ 3min.
Gas plug valves shall be tested for air tightness at 1.25 times the working pressure.
5, the same
pressure test method pneumatic valve
BUTTERFLY VALVE and shut-off valve strength test. The sealing performance test of the butterfly valve shall be introduced from the medium end to the test medium. The butterfly plate shall be opened and the other end closed. Fill the pressure to the specified value. After checking the packing and other seals for no leakage, close the butterfly plate and open the other end to check the butterfly. No leakage at the seal of the board is acceptable. As a butterfly valve for adjusting flow rate, sealing performance test may not be performed.
6. Diaphragm valve pressure test method
Diaphragm valve strength test from the introduction of media at either end, open the valve, the other end closed, the test pressure rose to the specified value, see the valve body and valve cover no leakage is qualified. Then step down to the leak test pressure, close the disc, open the other end of the inspection, no leakage is acceptable.
7, check valve pressure test method
Check valve test state: The lift check valve spool axis is in a horizontal and vertical position; the swing check valve passage axis and the valve flap axis are in a position approximately parallel to the horizontal line. (Shanghai Yonglong produced by the swing-type liquid ammonia check valve seat soft seal, test pressure has reached zero leakage effect)
In the strength test, the test medium is introduced from the inlet end to the specified value, and the other end is closed to see if the valve body and the valve cover have no leakage.
Sealing test The test medium was introduced from the outlet end, and the sealing surface was inspected at the inlet end. No leakage at the packing and gaskets was acceptable.
8, safety valve pressure test method
1 The strength test of a safety valve, like other valves, is tested using water. When the lower part of the valve body is tested, the pressure is introduced from the inlet I=I end and the sealing surface is closed. When the upper part of the valve body and the valve cover are tested, the pressure is introduced from the outlet end El and the other end is closed. No leakage of valve body and bonnet in the specified time is qualified.
2 Sealing test and constant pressure test, the general medium is: steam safety valve with saturated steam as test medium; ammonia or other gas valve with air as test medium; water and other non-corrosive liquid valves with water as test medium. Nitrogen is commonly used as a test medium for safety valves in some important locations.
The sealing test shall be conducted with the nominal pressure value as the test pressure, and the number of times shall not be less than twice. No leakage shall be qualified within the specified time. There are two methods for leak detection: one is to seal the joints of the safety valve, and the thin paper seal is attached to the El flange with grease, the thin paper bulges as a leak, and the bulge is not qualified; the second is using butter to thin The plastic plate or other plate is attached to the lower part of the outlet flange, and the valve is sealed with irrigation water to check that no bubbling occurs in the water. The number of safety valve constant pressure and seat back pressure tests shall not be less than 3 times and meet the regulations as qualified.
Yong Long A42F-25C ammonia safety valve performance test see GB/T12242-1989 safety valve performance test method.
9, Pressure Reducing Valve test method
1 The strength test of pressure reducing valve is generally assembled after a single test, and it can also be tested after assembly. Duration of strength test: lmin for DN <50mm; DN65 ~ 150mm for more than 2min; DN> 150mm for more than 3min.
After the bellows and the components were welded, the maximum pressure was 1.5 times after the application of the pressure reducing valve and the air was used for the strength test.
2 According to the actual working medium for sealing test. When tested with air or water, the test is performed at 1.1 times the nominal pressure; with the steam test, it is performed at the highest working pressure allowed at the operating temperature. The difference between the inlet pressure and the outlet pressure shall not be less than 0.2 MPa. The test method is: after the inlet pressure is set, the adjustment screw of the valve is gradually adjusted so that the outlet pressure can be sensitively and continuously changed within the range of the maximum and minimum values, without stagnation or jamming. For the steam pressure reducing valve, when the inlet pressure is removed, the valve is closed after the valve is closed, and the outlet pressure is the highest and lowest values. Within 2 minutes, the increase of the outlet pressure should comply with the requirements in Table 4.176-22. Meanwhile, the valve after the pipeline Volume compliance with the provisions in Table 4.18 is qualified; for water, air relief valve, when the inlet pressure is set, the outlet pressure is zero, close the valve to seal the test, no leakage within 2min is qualified.
A1BEST International Corporation
September 28, 2021
