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Test methods for various types of valves

The commonly used media for valve pressure testing include water, oil, air, steam, and nitrogen. The pressure test methods for various types of valves are as follows.

(1) Cut-off valve and throttle valve and throttle valve strength test, usually assembled valve in the pressure test frame, open the valve flap, inject medium to the specified value, check whether the valve body and valve cover take Sweat 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, strength tests may be done first, then depressurized to the sealability test value, check the packing and gaskets; then close the valve flap, open the outlet end and check the sealing surface for leakage.
(2) Gate valve
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 cover 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 and increase the valve test pressure to the specified value; then close the gate, open the blind plate at one end, and inspect the sealing surface for leakage. And then down, make the above repeated test until qualified.
Gate valve packing and gasket seal test shall be conducted before the gate seal test.
(3) Ball valve
The strength test of the ball valve should be performed with the ball half open.
1 Floating 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, turn the sphere no-load several times, the valve is in the closed state, introduce the test medium from one end to the specified value; check the sealing performance of the introduction end with a pressure gauge, use the pressure gauge accuracy 0.5 ~ 1st, 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 Three-way ball valves shall be tested for leaktightness at various positions.
(4) Plug Valves
1 When the plug valve is used for strength test, the medium is introduced from one end and the rest of the passage is closed. The plug is rotated to the fully open working positions in sequence to test. The valve body has not been found to be leaky.
2 In the leak test, the direct-flow cock should keep the pressure in the chamber equal to the passage, rotate the plug to the closed position, check from the other end, and then repeat the above test by rotating the plug 180°; three- or four-way plug valve 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.
Prior to the test of the plug valve, a layer of non-acidic dilute lubricating oil was allowed to be applied on the sealing surface. No leakage and enlarged water droplets were 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) Butterfly valve
The strength test of the butterfly valve is the same as the shut-off valve.
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 the flow rate, sealing performance test may not be performed.
(6) Diaphragm valve
Diaphragm valve strength test from the introduction of media at either end, open the valve flap, 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
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.
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
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 use of medium is: steam valve with saturated steam as the test medium; ammonia or other gas valve with air as the test medium; water and other non-corrosive liquid valves with water as the 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 for not less than twice and no leakage shall be qualified within the specified time. There are two methods for leak detection: one is to seal the connection points of the safety valve, and the thin paper seal is attached to the El flange with grease; the thin paper is bulging as a leak, and the bulge is not qualified; and the second is thinning with butter. 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.
For the performance test of safety valve, see GB/T 12242--1989 (Safety Valve Performance Test Method).
(9) Pressure reducing valve
1 The strength test of pressure reducing valve is usually assembled after a single test, and it can also be assembled and tested. 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 assembly were welded, the maximum pressure 1.5 times after the valve was applied and the air was used for the strength test.
2 According to the actual working medium, the sealing performance 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 is not 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 min, the increase of the outlet pressure should meet the requirements in Table 4.176-22, and the valve rear 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.

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