A complete set of pressure test methods for industrial valves
Generally, industrial valves are not subject to strength test in use, but after repair, the valve body and bonnet or the valve body and bonnet damaged by corrosion shall be subject to strength test. For safety valve, its constant pressure, reseating pressure and other tests shall conform to the specifications and relevant regulations. Before valve installation, valve strength test and valve sealing test shall be conducted on the valve hydraulic test bench. Spot check 20% of low-pressure valves, 100% of unqualified ones; 100% of medium and high-pressure valves.
- Pressure test method of stop valve and throttle valve
- Pressure test method of gate valve
- Pressure test method of ball valve
- Pressure test method of plug valve
- Pressure test method of butterfly valve
- Pressure test method of diaphragm valve
- Pressure test method of check valve
- Pressure test method of safety valve
- Pressure test method of pressure reducing valve
- Management regulations for valve pressure test
The commonly used media for valve pressure test are water, oil, air, steam, nitrogen, etc. the pressure test methods for various industrial valves including pneumatic valves are as follows:
01. Pressure test method of stop valve and throttle valve
For the strength test of stop valve and throttle valve, the assembled valve is usually placed in the pressure test frame, the disc is opened, the medium is injected to the specified value, and the valve body and bonnet are checked for sweating and leakage. The strength test can also be carried out on a single piece. Only stop valve is used for sealing test. During the test, the valve stem of the stop valve is in a vertical state, the valve disc is opened, and the medium is introduced from the bottom end of the valve disc to the specified value, and the packing and gasket are checked; after the valve disc is qualified, close the valve disc, and open the other end to check whether there is leakage. If the strength test and sealing test of the valve are to be done, the strength test can be done first, then the pressure can be reduced to the specified value of the sealing test, and the packing and gasket can be checked; then the valve disc can be closed, and the outlet end can be opened to check whether the sealing surface leaks.
02. Pressure test method of gate valve
The strength test of gate valve is the same as that of stop valve. There are two methods for sealing test of gate valve.
- ① Open the ram to make the pressure in the valve rise to the specified value; then close the ram, take out the gate valve immediately, check whether there is leakage at the seals on both sides of the ram or directly inject the test medium into the plug on the valve cover to the specified value, and check the seals on both sides of the ram. The above method is called intermediate pressure test. This method is not suitable for sealing test of gate valve with nominal diameter less than dn32mm.
- ② Another method is to open the ram to raise the test pressure of the valve to the specified value; then close the ram and open the blind plate at one end to check whether the sealing surface leaks. Turn over the head again and repeat the above test until it is qualified.
The sealing test of packing and gasket of pneumatic gate valve shall be conducted before the sealing test of gate valve.
03. Pressure test method of ball valve
The strength test of pneumatic ball valve shall be carried out under the condition that the ball is half open.
- ① Sealing test of floating ball valve: put the valve in a half open state, one end is led into the test medium, and the other end is closed; turn the ball several times, open the closed end when the valve is in a closed state, and check the sealing performance of the packing and gasket at the same time, without leakage. Then introduce the test medium from the other end and repeat the above test.
- ② Sealing test of the fixed ball valve: before the test, turn the ball several times without load, and the fixed ball valve is in the closed state, and lead the test medium from one end to the specified value; check the sealing performance of the lead-in end with the pressure gauge, and the accuracy of the pressure gauge is 0.5-1 level, and the range is 1.6 times of the test pressure. If there is no pressure drop within the specified time, it is qualified; then introduce the test medium from the other end and repeat the above test. Then, the valve is half open, both ends are closed, and the inner cavity is filled with medium. Under the test pressure, check the packing and gasket, and there is no leakage.
- ③ Three way ball valve shall be subject to sealing test at all positions.
04. Pressure test method of plug valve
- ① During the strength test of the plug valve, the medium is introduced from one end, the rest channels are closed, and the plug is rotated to the fully open working positions in turn for the test. If no leakage is found in the valve body, it is qualified.
- ② During the sealing test, the straight plug shall keep the pressure in the cavity equal to that in the passage, rotate the plug to the closed position, check from the other end, and then rotate the plug 180 ° to repeat the above test; the three-way or four-way plug valve shall keep the pressure in the cavity equal to that at the passage end, rotate the plug to the closed position in turn, and introduce the pressure from the right angle end to the other end at the same time. Line check.
It is allowed to apply a layer of non acid thin lubricating oil on the sealing surface before the test bench of the plug valve. If no leakage or enlarged water drop is found within the specified time, it is qualified. The test time of plug valve can be shorter, generally 1-3min according to the nominal diameter.
The plug valve for gas shall be tested for air tightness at 1.25 times the working pressure.
05. Pressure test method of butterfly valve
The strength test of pneumatic butterfly valve is the same as that of stop valve. For the sealing performance test of butterfly valve, the test medium shall be introduced from the end of medium flow, the butterfly plate shall be opened, the other end shall be closed, and the injection pressure shall be up to the specified value; after checking that there is no leakage at the packing and other sealing places, close the butterfly plate, open the other end, and check that there is no leakage at the sealing place of butterfly plate, it is qualified. As the butterfly valve for regulating flow, the sealing performance test is not required.
06. Pressure test method of diaphragm valve
In the strength test of diaphragm valve, medium is introduced from either end, the disc is opened, and the other end is closed. When the test pressure rises to the specified value, it is qualified if there is no leakage in the valve body and bonnet. Then reduce the pressure to the sealing test pressure, close the valve disc, open the other end for inspection, no leakage is qualified.
07. Pressure test method of check valve
Check valve test status: lift check valve disc axis is at a position perpendicular to the horizontal; swing check valve channel axis and disc axis are at a position approximately parallel to the horizontal.
During the strength test, the test medium shall be introduced from the inlet end to the specified value, and the other end shall be closed to see if there is no leakage in the valve body and bonnet.
The sealing test shall be conducted by introducing the test medium from the outlet end and checking the sealing surface at the inlet end. If there is no leakage at the packing and gasket, it is qualified.
08. Pressure test method of safety valve
- ① The strength test of safety valve is the same as that of other valves, and it is tested with water. When testing the lower part of the valve body, the pressure is introduced from the I = I end, and the sealing surface is closed; when testing the upper part of the valve body and the bonnet, the pressure is introduced from the El end, and the other ends are closed. The valve body and bonnet shall be qualified if there is no leakage within the specified time.
- ② For tightness test and constant pressure test, the commonly used medium is: saturated steam is used as test medium for safety valve for steam; air is used as test medium for valve for ammonia or other gases; water is used as test medium for valve for water and other non corrosive liquids. For some important safety valves, nitrogen is often used as the test medium.
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 two, and it is qualified if there is no leakage within the specified time. There are two methods for leakage inspection: one is to seal the joints of the safety valve, seal the thin paper on the outgoing El flange with butter, if the thin paper is bulging, it is leakage, if it is not bulging, it is qualified; the other is to seal the thin plastic plate or other plates on the lower part of the outlet flange with butter, seal the valve disc with water, and if there is no bubble in the inspection water, it is qualified. The times of constant pressure and reseating pressure test of safety valve shall not be less than 3, and it is qualified if it meets the requirements.
See GB / T 12242-1989 safety valve performance test method for performance test of safety valve.
- ① The strength test of pressure reducing valve is generally assembled after single piece test, or after assembly test. Duration of strength test: 1min for DN < 50mm; 2min for DN 65-150 mm; 3min for DN > 150 mm.
- After the bellows is welded with the components, the strength test shall be carried out with air at 1.5 times of the maximum pressure after the application of the pressure reducing valve.
- ② The sealing test shall be conducted according to the actual working medium. When testing with air or water, the test shall be conducted at 1.1 times of the nominal pressure; when testing with steam, the test shall be conducted at the maximum allowable working pressure under the working temperature. The difference between the inlet pressure and the outlet pressure shall not be less than 0.2MPa. The test method is: after the inlet pressure is set, gradually adjust the adjusting screw of the valve so that the outlet pressure can change sensitively and continuously within the range of maximum and minimum values, without stagnation or jamming. For the steam pressure reducing valve, when the inlet pressure is adjusted away, close the block valve behind the valve, and the outlet pressure is the highest and lowest value. Within 2min, the appreciation of the outlet pressure shall meet the requirements of table 4.176-22, and the volume of the pipeline behind the valve shall meet the requirements of table 4.18, which is qualified. For the water and air pressure reducing valve, when the inlet pressure is adjusted and the outlet pressure is zero, close the pressure reducing valve for sealing. The test is qualified if there is no leakage within 2min.
- 1. Visual inspection shall be carried out for all valves after unpacking, including complete nameplate on valve body, product quality certificate documents, valve in closed state, no blue surface and other damages, no dirt, protective covers at both ends, etc.
- 2. The operator shall be familiar with the operation of the test bench.
- 3. JHA of valve pressure test is perfect. Operators shall be familiar with and have corresponding preventive measures for safety hazards in the process of valve pressure test and transportation.
- 4. Valve pressure test process: valve shell strength test, upper sealing test and sealing test.
- (1) The valve shell strength test medium is water, the pressure is 1.5 times of the nominal pressure of the valve, the pressure holding time is 5min, and it is qualified if there is no leakage or moisture.
- (2) Water is used as the sealing test medium on the valve, the pressure is 1.5 times of the nominal pressure, the pressure holding time DN ≤ 50 is 15s, 65 ≤ DN ≤ 300 is 60s, DN ≥ 350 is 120s, no leakage is qualified.
- (3) Low pressure sealing test shall be carried out for valve sealing test. Air (gate valve) shall be used as test medium, with pressure of 0.6MPa, pressure holding time of 15s for DN ≤ 50, 60s for 65 ≤ DN ≤ 150, 120s for DN ≥ 200, and qualified if the permeability meets the requirements.
- (4) After the pressure test is qualified, the water in the valve chamber shall be dried with compressed air in time.
- (5) Mark √ on the valve body for the qualified valve in pressure test, and mark × on the unqualified valve.
- (6) After pressure test, the valves shall be stacked separately according to the model and specification of the device, and the unqualified products shall be stacked separately; each stacking area shall be provided with obvious signboards. After the pressure test, the valve shall be covered back and protected with colored strip cloth in the stacking area.
- (7) After the valve pressure test, fill in the valve / pipe fitting test record according to the device in time, and fill in the purchase contract number on the valve body in the model column.
- (8) For the distribution of qualified valves, the valve distribution record shall be filled in and signed by both parties.
- (9) Information account of unqualified valves shall be established separately for unqualified valves.
Source: China Valve Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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