Pressure test methods for various valves

Pressure test methods for various valves

 

Under normal circumstances, industrial valves are not tested for strength during use, but the valve body and bonnet or corrosion damped valve body and bonnet should be tested for strength after maintenance.

 

For safety valves, tests such as set pressure and return pressure should comply with specifications and relevant regulations.

 

Valve installation should be tested for strength and leak tightness.

 

Low pressure valve check 20%. If it fails, it should be checked 100%; medium and high pressure valves should be checked 100%.

 

Common valve pressure test media are water, oil, air, steam, nitrogen and so on. The pressure test methods of various industrial valves with pneumatic valves are as follows:

 

 1. Ball pressure test method

 

The strength test of the pneumatic ball valve should be carried out when the ball is half open.

 

 1Float ball valve tightness test: The valve is in half position-open state, the test medium is introduced at one end, and the other end is closed; the ball valve is rotated several times, and the closed end is opened when the valve is closed. Check the sealing performance of the packing and gasket.

 

No leakage needed.

 

Then introduce the test medium from the other end and repeat the test.

 

 2 Fixed ball valve tightness test: Before the test, the ball idles several times. After the fixed ball valve is closed, the test medium is introduced from one end to the specified value; the pressure at the inlet is used to check the sealing performance of the front end and the accuracy of the pressure gauge is used.

 

. 5 to 1 level, the range is 1.5 times the test pressure.

 

Decompression cannot be performed within the specified time; then the test medium is introduced from the other end and the above test is repeated.

 

Then, the valve is in a half-open state, the end is closed, the inner cavity is filled with the medium, and the packing and gasket are checked under the test pressure, and there is no leakage.

 

 3 Three-way ball valves should be leak tested at various locations.

 

 2. Pressure test method of check valve

 

Check valve test status: The lift check valve disk axis is located perpendicular to the horizontal position; the swing check valve channel axis and the baffle axis are located approximately parallel to the horizontal line.

 

In the strength test, the test medium is introduced into the specified value from the inlet end, and the other end is closed, and the valve body and the valve cover do not leak.

 

The sealing test introduces the test medium from the outlet end. Check the sealing surface at the inlet end for no leakage of packing and gaskets.

 

 3. Pressure test method of pressure reducing valve

 

 1 The strength test of the pressure reducing valve is generally assembled after a single piece test, and the test can also be performed after assembly.

 

Strength test duration: lmin of DN × 1mm; DN65-150mm exceeds 2min; DN \\ u003e150mm exceeds 3 minutes.

 

After the bellows and components are welded, the pressure of the pressure reducing valve is applied 1.5 times, and the strength test is performed with air.

 

 2 Seal test according to the actual working medium.

 

When testing with air or water, the test is performed at 1.1 times the nominal pressure; when using the steam test, the higher working pressure allowed at the operating temperature.

 

The difference between the inlet pressure and the outlet pressure is not less than 0.2MPa.

 

The test method is as follows: After setting the inlet pressure, gradually adjust the adjusting screw of the valve to make the outlet pressure change continuously and sensitively within a range of larger and smaller values ​​without stagnation or interference.

 

For steam pressure reducing valves,

 

When the inlet pressure is removed, the valve closes after the valve is closed, and the outlet pressure is higher and lower. Within 2 minutes, the outlet pressure should increase according to Table 4.176-22. At the same time, the volume of the pipeline behind the valve meets the requirements of Table 4.18.

 

For water and air pressure reducing valves, when the inlet pressure is set and the outlet pressure is zero, the pressure reducing valve is closed for a seal test, and there is no leakage within 2 minutes.

 

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 4, butterfly valve pressure test method

 

The strength test of the pneumatic butterfly valve is the same as that of the globe valve.

 

The test of the sealing performance of the butterfly valve shall be introduced from the test medium at the end of the flow of the medium. The disc should be open and the other end should be closed. The injection pressure should be the specified value. After checking that the packaging and other seals are not leaking, close the disc and open the other end to inspect the butterfly.

 

It is acceptable for the plate seal to leak free.

 

As a butterfly valve that regulates flow, it may not be possible to perform a seal performance test.

 

 5. Pressure test method of plug valve

 

 1 When testing the strength of the valve when plugging in, introduce the medium from one end, close the remaining passages, and rotate the plug to the fully open working position for testing. No body was found to be acceptable.

 

 2 In the sealing test, the straight plug should keep the pressure in the cavity equal to the channel pressure, rotate the plug to the closed position, check from the other end, and then rotate the plug 180 ° to repeat the above test; three-way or four-way plug valve

 

The pressure in the chamber should remain equal to the end of the channel. The plugs should be rotated to the closed position in turn, pressure is introduced from the right-angled end, and inspection is performed simultaneously from the other end.

 

Prior to the plug valve test, non-acid allowed the application of thin lubricating oil on the sealing surface, and no leaks and increased water droplets were found for a specified period of time.

 

The test time of the plug valve can be shorter, usually 1 to 3 minutes according to the nominal diameter.

 

Gas stopcocks should be tested for airtight pressure at 1.25 times operation.

 

 6. Pressure test method of diaphragm valve

 

Diaphragm valve strength test introduces medium from both ends, opens the flap, and closes the other end. After the test pressure rises to the specified value, the valve body and bonnet will not leak.

 

The pressure was then reduced to the seal test pressure, the disc was closed, and the other end was opened for inspection. No leakage was acceptable.

 

 7. Pressure test methods for globe and throttle valves

 

For the strength test of the shut-off valve and the throttle valve, the assembled valve is usually placed on a pressure test stand, the valve flap is opened, the injected medium reaches the specified value, and the valve body and the valve cover are checked for sweating and leakage.

 

The strength test can also be performed in one piece.

 

The seal test is used only as a stop valve.

 

During the test, the stem of the shut-off valve is in the vertical state, the valve disc is opened, the medium introduces the specified value from the lower end of the valve disc, packing and inspection gasket; after passing, close the valve disc and open the other end to check for leaks.

 

If you want to perform the valve strength and tightness test, you can perform the strength test first, then reduce the pressure to the specified value of the seal test, and check the packing and gasket; then close the valve flap, open the outlet end, and check whether the sealing surface is leaking.

 

 8. Pressure test method of gate valve

 

The strength test of the gate valve is the same as that of the stop valve.

 

There are two ways to seal the gate valve.

 

 1 Open the gate and increase the pressure in the valve to the specified value; then close the gate and immediately remove the gate valve to check whether there are leaks or straight lines on the seals on both sides of the gate.

 

Inject the test medium into the plug on the bonnet to the specified value and check the seal on both sides of the plunger.

 

The above method is called a medium voltage test.

 

This method is not applicable to the sealing test of gate valves with a nominal diameter below DN32mm.

 

 2 Another method is to open the gate and increase the valve test pressure to the specified value; then close the shutters and open the blind plate at one end to check whether the sealing surface is leaking.

 

Then go back and repeat the test until it passes.

 

Pneumatic gate valve packing and gasket sealing tests shall be carried out before the sealing test. ## #9. Pressure test method of safety valve

 

 1 The strength test of the safety valve is the same as other valves, and the test is performed with water.

 

When testing the lower part of the valve body, pressure is introduced from the I = I end and the sealing surface is closed. When testing the upper part of the valve body and bonnet, pressure is introduced from the E1 end and the other end is closed.

 

The valve body and bonnet did not leak within the specified time.

 

 2 Sealing test and constant pressure test, the general medium used is: steam safety valve with saturated steam as the test medium; ammonia or other gas valves with air as the test medium; water and other non-corrosive liquid valves with water as the test

 

medium.

 

For some important positions of the safety valve, nitrogen is usually used as the test medium.

 

The sealing test is carried out with the nominal pressure value as the test pressure, the number of which is not less than two, and no leakage is allowed within the specified time.

 

There are two types of leak detection methods: one is to seal the joint of the safety valve, the thin paper is sealed with butter on the El flange, the tissue swells to leak, and the protrusion is unqualified; the second is to dilute with butter

 

A plastic plate or other plate is sealed at the lower part of the outlet flange, and the valve disc is filled with water. Check for water bubbles.

 

The number of constant pressure and back pressure tests of the safety valve is not less than 3, and the requirements are qualified.

 

For the performance test of the safety valve, refer to GB / T 12242-1989 Safety valve performance test method.

 

Valve pressure management regulations

 

 1. After opening the box, all valves should be checked, including the complete nameplate on the valve body, product quality certification, whether the valve is closed, and no other damage, such as blue surface, no stains, and protective covers at both ends. \\ r \\?

 

 2. The operator should be familiar with the operation of the test bench.

 

 3. Valve pressure test JHA is good. Operators should be familiar with the safety hazards of valve pressure test, reverse transportation and other processes. Valve pressure test process: valve shell strength test, upper seal test, seal test.

 

(1) The strength of the valve casing is water, the pressure is 1.5 times the nominal pressure of the valve, the residence time is 5 minutes, and there is no dripping or damp conditions.

 

(2) The sealing test medium on the valve uses water, the pressure is 1.5 times the nominal pressure, the residence time DN≤50 is 15s, 65≤DN≤300 is 60s, and DN≥350 is 120s. No leakage is qualified.

 

(3) Valve sealing test Perform low pressure sealing test. The test medium is air (gate valve), the pressure is 0.6 MPa, the residence time DN ≤ 50 is 15 s, 65 ≤ DN ≤ 150 is 60 s, and DN ≥ 200 is 120 s. The penetration force is the same.

 

Qualified.

 

(4) It should be used in time after the test pressure is passed.

 

The compressed air blows out dry water from the valve chamber.

 

(5) Valves with valve pressure test are marked on the valve body, and unqualified valves are marked with ×.

 

# ## (6) After the pressure test, the valves should be stacked separately according to the model and specifications, and the unqualified products should be stacked separately; each stacking area should have obvious signs.

 

After the pressure test, the valve shall be covered with a cover and covered with colored bands in the storage area.

 

(7) After the valve pressure test, fill in "valve" / installation test record "in time according to the equipment, and fill in the purchase contract number on the valve body in the model column.

 

(8) Valves issued for testing shall be filled in the valve "valve release record" and signed by both parties.

 

(9) Unqualified valves need to be established