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Pressure Test Methods For Various Industrial Valves

Under normal circumstances, industrial valves are not used for strength test, but the valve body and cover after repair or corrosion damage to the valve body and bonnet should be strength test. For safety valves, the constant pressure and back pressure and other tests should be consistent with the instructions and the relevant regulations. Before the valve should be installed on the valve hydraulic test bench for valve strength test and valve seal test. Low-pressure valve checks 20%, such as failure should be 100% of the inspection; medium and high pressure valves should be 100% inspection. Valve pressure test medium commonly used water, oil, air, steam, nitrogen, etc., all kinds of industrial valves with pneumatic valve pressure test method is as follows:


1, cut-off valve and throttle pressure test method

Shut-off valve and throttle strength test, usually the assembly of the valve on the pressure test rack, open the valve flap, the media injected to the specified value, check the body and the valve cover is sweating and leakage. Can also be a single strength test. Sealing test only make the globe valve. Test the valve stem of the valve into a vertical state, the valve open, the medium from the valve at one end of the lower end of the introduction to the specified value, check the filler and gasket; to be closed after the valve flap, open the other end to check for leakage. If the valve strength and tightness test to be done, the strength test can be done, and then step down to the tightness test values, check the filler and gasket; and then close the valve flap, open the outlet to check the sealing surface for leakage.


2, gate pressure test method

Gate valve strength test and the same cut-off valve. Gate valve sealing test in two ways.

① gate open, so that the valve pressure rose to the required value; and then close the gate, immediately remove the gate valve to check whether the seal on both sides of the seal leakage or directly to the plug on the valve cap test medium injection to the specified value , Check the seal on both sides of the gate. The above method is called intermediate pressure test. This method should not be less than the nominal diameter of DN32mm valve seal test.

② Another method is to open the gate, the valve test pressure rose to the required value; and then close the gate, open the blind end of the one, check the sealing surface for leakage. Go down again and repeat the test until it is qualified.

Pneumatic valve packing and gasket sealing test should be carried out before the gate seal test.


3, ball valve pressure test method

Pneumatic ball valve strength test should be carried out in the ball half-open state.

① floating ball valve sealing test: the valve is half-open state, one end of the introduction of test medium, the other end is closed; the ball rotates several times, the valve is closed, open the closed end inspection, packing and gasket at the same time check the sealing performance, There may be no leakage. Then introduce the test medium from the other end and repeat the above test.

② fixed ball valve sealing test: Before the test the ball no-load rotation several times, the fixed ball valve is closed, from one end of the introduction of test medium to the specified value; check the pressure gauge seal performance, the use of pressure gauge accuracy of 0 .5 to 1 level, the range of 1.6 times the test pressure. Within the stipulated time, there is no step-down phenomenon qualified; then from the other end of the introduction of test medium, repeat the above test. Then, the valve is half-open state, closed at both ends, the cavity is filled with media, check the packing and gasket under the test pressure, there should be no leakage.

③ three-way ball valve should be carried out in all positions on the tightness test.


4, plug the pressure test method

① plug the strength of the test, the media introduced from one end, the closure of the remaining access, the plug in turn all open to the working position of the test, the valve did not find leakage as qualified.

② tightness test, the straight-type plug should keep the cavity and the access pressure equal to the plug rotated to the closed position from the other end of the inspection, and then the plug rotated 180 ° repeat the above test; three-way or four-way plug valve The pressure in the chamber should be kept equal to the pressure at one end of the passage, and the stopper should be rotated to the closed position one after the other. The pressure should be introduced from the right-angle end and be inspected from the other end at the same time.

Stopper valve test bench in front of the coating surface to allow a layer of non-acid dilute lubricating oil, within a specified time did not find leakage and expansion of the water droplets as qualified. Stopcock test time can be shorter, usually according to the provisions of the nominal diameter of l ~ 3min.

Plug valves for gas should be 1.25 times the working pressure of air tightness test.


5, butterfly pressure test method

 Pneumatic butterfly valve strength test and the same cut-off valve. Butterfly valve sealing performance test should be introduced from the media end of the test medium, the disc should be open, the other end is closed, the injection pressure to the specified value; check the packing and other seals no leakage, close the disc, open the other end, check the butterfly No seal leakage at the board as qualified. As a butterfly valve used to regulate the flow of sealing performance test.


6, diaphragm pressure test method

 Diaphragm valve strength test from either end of the introduction of media, open the valve flap, the other end is closed, the test pressure rose to the specified value, see the valve body and valve cover no leakage as qualified. Then pressure to seal test pressure, close the valve flap, open the other end of the inspection, no leakage of qualified.


7, check valve pressure test method

 Check valve test state: lifting check valve disc axis in a horizontal position; swing check valve channel axis and the valve axis in the horizontal line with the approximate parallel position.

 Strength test, the introduction of test media from the import side to the specified value, the other end of the closed, see the valve body and valve cover no leakage as qualified.

 Leakage test From the outlet end of the introduction of the test medium, check the sealing surface at the inlet, packing and gasket at no leakage as qualified.


8, safety valve pressure test method

① safety valve strength test and other valves, water is used for testing. When testing the lower part of the valve body, the pressure is introduced into the 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 El end and the other end is sealed. Valve body and bonnet within the specified time no leakage of qualified.

 ② sealing test and constant pressure test, the general use of the medium are: steam safety 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 valve with water as a test medium. For some important position of the safety valve commonly used nitrogen as the test medium.

 Seal test Nominal pressure as the test pressure test, the number of not less than twice, within the specified time without leakage as qualified. There are two ways to check the leak: First, the safety valve seal at the junction of the thin paper with butter seal affixed to the El flange, thin tissue bulging for the leak, not up for qualified; the second is the butter thin Plastic plates or other boards sealed in the lower part of the export flange, irrigation valve flap seal, check the water bubble is not qualified. Safety valve pressure and back pressure test number of times not less than 3 times, in line with the provisions of qualified.

  Safety valve performance test see GB / T 12242-1989 safety valve performance test method. "


9, pressure relief valve pressure test method

(1) The strength test of the pressure reducing valve is usually assembled after the single piece test, and can also be assembled and tested. Intensity test duration: DN <50mm lmin; DN65 ~ 150mm greater than 2min; DN> 150mm greater than 3min.

After the bellows and the components are welded, 1.5 times the maximum pressure after the pressure reducing valve is applied, and the strength test is carried out with air.

② sealing test according to the actual working medium. When tested with air or water, the test is to be carried out at 1.1 times the nominal pressure; with the steam test, the maximum working pressure is allowed at the working temperature. Import pressure and export pressure difference of not less than 0.2MPa. The test method is as follows: after the inlet pressure is adjusted, the adjusting screw of the valve is gradually adjusted so that the outlet pressure can change sensitively and continuously within the range of maximum and minimum, without stagnation or jamming phenomenon. On the steam valve, when the inlet pressure transferred away, shut off the valve after the cut-off valve, the outlet pressure is the highest and lowest values within 2min, the outlet pressure rise should meet the provisions of Table 4.176-22 at the same time, the valve after the pipeline Volume compliance with the provisions of Table 4.18 qualified; water, air relief valve, when the inlet pressure is set, the outlet pressure is zero, close the valve for leak test, no leakage within 2min qualified.


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