How to check and test the valve when purchasing the valve?
1, inspection scope
If the buyer does not specify other additional items in the order contract, the inspection shall be limited to the following:
a) inspect the valve during the assembly process using non-destructive inspection tools and methods as specified in the order contract ;
b) The visual inspection of castings shall comply with the provisions of JB/T 7929;
c) “mandatory” and “optional” stress tests;
d) other supplementary tests;
e) Review processing records and non-destructive testing records (including prescribed radiographic records).
Note: All inspections should be carried out in accordance with written procedures prepared by the corresponding standards.
2, inspection
2.1 The valve manufacturer shall perform visual inspection of all castings of valve bodies, bonnets and seals to ensure compliance with JB/T 7929.
2.2 The valve manufacturer shall inspect each valve to ensure compliance with the requirements of this standard and related product standards.
Pressure test
1 Test location
The pressure test should be carried out by the valve manufacturer at the valve manufacturer.
2 test equipment
Equipment used for pressure testing shall not have an external force applied to the seal of the seat during the test.
3 test requirements
3.1 Each valve shall be pressure tested in accordance with Table 1 or Table 2.
3.2 Valves with a nominal diameter less than or equal to 100mm, a nominal pressure less than or equal to 25.0MPa and a nominal diameter greater than or equal to 125mm and a nominal pressure less than 10.0Mpa shall be tested in accordance with Table 1.
3.3 Valves with a nominal diameter less than or equal to 100mm, a nominal pressure greater than 25.0Mpa and a nominal diameter greater than or equal to 125mm and a nominal pressure greater than 10.0Mpa shall be tested in accordance with Table 2.
Table 1 pressure test
Pilot projects | Valve gate type Type | |||||
Gate valve | Shut-off valve | Plug valve | Check valve | Floating ball valve | Butterfly valve and fixed ball valve | |
Shell body | have to | have to | have to | have to | have to | have to |
Upper seal 1 ) | have to | have to | Not applicable | Not applicable | Not applicable | Not applicable |
Low pressure seal | have to | Optional | Must 2 ) | Choose 3 ) | have to | have to |
High pressure seal 4 ) | Optional | Must be 5 ) | Optional 2 ) | have to | Optional | Optional |
1) All valves with upper sealing performance shall be subjected to an upper sealing test, except for bellows sealing valves. 2) For oil- sealed plug valves , high-pressure seal test is required, and low-pressure seal test is optional; 3) If the consent of the purchaser agrees, the valve manufacturer may replace the high pressure seal test with a low pressure seal test; 4) After the high-pressure sealing test, the elastic sealing valve may reduce its sealing performance under low pressure conditions; 5) For power-driven shut-off valves , the test pressure for the high-pressure seal test shall be 110% of the design differential pressure used for the selected power drive . | ||||||
Table 2 pressure test
Pilot projects | Valve gate type Type | |||||
Gate valve | Shut-off valve | Plug valve | Check valve | Floating ball valve | Butterfly valve and fixed ball valve | |
Shell body | have to | have to | have to | have to | have to | have to |
Upper seal 1 ) | have to | have to | Not applicable | Not applicable | Not applicable | Not applicable |
Low pressure seal | have to | Optional | have to | Choose 2 ) | have to | have to |
High pressure seal 3 ) | Optional | Must be 4 ) | Optional | have to | Optional | Optional |
1) For valves with upper sealing performance, the upper sealing test shall be performed, except for bellows sealing valves. 2) If the consent of the purchaser agrees, the valve manufacturer may replace the high pressure seal test with a low pressure seal test; 3) After the high-pressure sealing test, the elastic sealing valve may reduce its sealing performance under low pressure conditions; 4) For power-driven shut-off valves, the test pressure for the high-pressure seal test shall be 110% of the design differential pressure used for the selected power drive . | ||||||
3.4 Unless otherwise stated in the order contract, for the valve with the upper sealing performance, the upper sealing test may be a high pressure sealing test or a low pressure sealing test, which is selected by the manufacturer.
4 high pressure seal test
In Tables 1 and 2, there are several types of valves that must be subjected to high pressure seal tests. Some types of valves have optional high pressure seal tests, but these valves should pass the high pressure seal test (as a test for valve seal structures). ).
5 test medium
5.1 The test medium for shell test, high pressure seal test and high pressure seal test shall be water, air, kerosene or a non-corrosive liquid with a viscosity not higher than water. The temperature of the test medium does not exceed 52 °C. The test medium temperature of the cryogenic valve can be specified in the order.
5.2 Low pressure seal and low pressure upper seal test, the test medium should be air or inert gas.
5.3 When performing shell test, seal test and upper seal test with air or other gases, the manufacturer shall color the correct leak detection method. When testing with water or liquid, the air inside the valve should be removed.
5.4 The water used for each test may contain water-soluble oil or rust inhibitor. When required by the purchaser, the water may contain lubricant. For austenitic stainless steel valves, the amount of chloride in the water used should not exceed 100 mg/L.
6 Shell test of high pressure gas
6.1 When the shell test for high pressure gas is required as specified in the order contract, the test shall be carried out after the shell liquid test and corresponding safety measures shall be taken.
6.2 The test pressure of the shell of high-pressure gas is 1.1 times of the maximum allowable working pressure at 38 °C or according to the contract of the order, no visible leakage is allowed during the test.
7 test pressure
7.1 The test pressure of the shell is 1.5 times the maximum allowable working pressure at 38 °C.
7.2 The high pressure seal test and the high pressure upper seal test pressure are 1.1 times the maximum allowable working pressure at 38 °C.
7.3 Low pressure seal test and low pressure upper seal test pressure is 0.4~0.7MPa.
7.4 According to the butterfly valve specified by the user's procurement specifications, the sealing test pressure is 1.1 times the design pressure difference.
7.5 The sealing test pressure of the check valve is the nominal pressure at 38 °C.
8 test duration
For each test, the minimum time for the test to maintain the test pressure is as specified in Table 3.
Table 3 maintains the duration of the test pressure
Valve specification DN Mm | Keep test pressure for the shortest duration t | ||||
Shell body | Upper seal | Tight seal | |||
Check valve | Other valves | Check valve | Other valves | ||
≤50 | 60 | 15 | 15 | 60 | 15 |
65~150 | 60 | 60 | 60 | 60 | 60 |
200~300 | 60 | 120 | 60 | 120 | |
≥350 | 120 | 300 | 120 | 120 | |
Note: Keeping the test pressure for the shortest duration is the minimum time to maintain the specified test pressure after the test medium pressure in the valve rises to the specified value. | |||||
9 leakage
9.1 No visible leakage is allowed for shell fatigue and upper seal tests. If the test medium is liquid, there shall be no visible droplets or surface moisture. If the test medium is air or other gas, there should be no air bubbles leaking out. There should be no structural damage during the test.
9.2 For the low-pressure seal test and the high-pressure seal test, obvious visible leakage is not allowed to pass through the valve, the valve seat and the valve body contact surface, etc., and there is no structural damage. During the test duration, the test medium passes through the sealing surface. The allowable leak rate is shown in Table 4.
Table 4 Maximum allowable leak rate for seal test
Valve specification DN Mm | All elastic sealing valves Drop /mm Bubble /min | All metal seal secondary valves except check valves | Metal seal secondary check valve | ||
Liquid test 1) Drop /min | Gas test Bubble /min | Liquid test mL/min | Gas test m 3 /h | ||
≤50 | 0 | 0 2) | 0 2) | (DN/25)*3 | (DN/25)*0.042 |
65~150 | 12 | twenty four | |||
200~300 | 20 | 40 | |||
≥350 3) | 28 | 56 | |||
1) For the liquid test, 1 mL (cm 3 ) is equivalent to 16 drops. 2) No leakage during the specified minimum test time ( see Table 3) . For liquid tests, “ 0 ” drops indicate no visible leakage during each specified minimum test time. For gas tests, “ 0 ” bubble indicates The amount of leakage is less than 1 bubble in each specified minimum test time . 3) For check valves with a diameter greater than DN600mm , the allowable leakage should be agreed between the supplier and the buyer . | |||||
9.3 For valves such as ceramics and non-metallic sealing pairs, the allowable leakage rate of the sealing test shall be as specified in Table 4 for metal sealing valves of the same type and specification.
Pressure test method
1 General requirements
1.1 For special structural valves (except for oil-sealed plug valves) that allow for the injection of emergency seal grease to the sealing or packing area, the injection system shall be empty and inoperative during the test.
1.2 When testing with liquid, the air in the chamber should be drained.
1.3 Prior to shell testing, the valve shall not be painted or coated with other coatings that may obscure surface defects (for phosphating or similar chemical treatment to protect the valve surface, use prior to testing is permitted, but should not mask voids, Defects such as stomata and blisters).
1.4 When the gate valve , plug valve and ball valve seal test are carried out, the body cavity between the valve cover and the sealing surface should be filled with medium and pressurized to the test pressure to avoid sealing due to the gradual filling of the medium and pressure into the above part during the test. The leak was not detected.
1.5 When performing the sealing test, no external force affecting the leakage of the sealing surface should be applied at both ends of the valve. The operating torque of the closing valve should not exceed the closing torque of the valve design.
2 shell test
2.1 Pressurize the installed valve body cavity, both ends of the valve are closed, and the opening and closing parts are partially opened. During the test, there should be no leakage at each joint. Except for the bellows sealing valve, the packing gland is pressed enough to maintain the test pressure, so that the stuffing box part is tested, and there should be no leakage at the stuffing box during the test.
2.2 Valves that are not adjustable for the stem seal (such as “O” rings, single-layer seals or similar packings) should be leak-free at the seal of the housing.
3 Valves with upper sealing performance (except bellows valves) shall be subjected to an upper sealing test.
During the upper seal test, both ends of the valve are closed, and the valve body is pressurized in the assembled valve body. The valve should be fully opened to release the packing gland. The test is carried out after the shell test. The valve manufacturer shall not use the valve with the upper seal test as the basis for the recommended valve to add or replace the packing when the pressure is applied.
4 low pressure seal test
4.1 During the test, the sealing surface shall be kept clean and free of oil (but not applicable to valves with lubricating oil as the main sealing function). In order to prevent the sealing surface from being scratched, an oil film not thicker than the kerosene film may be applied.
4.2 Low pressure seals shall be carried out in one of the following ways:
a) For two-way sealed valves (except for multi-channel valves and shut-off valves), pressurize each end of the closed valve and open the other end to the atmosphere to check for leakage at the sealing surface at the outlet end.
Valves that are sealed in one direction and marked with a direction of media flow should be pressurized at the inlet end. For check valves, pressurize at the outlet end.
Fill the sealing surface of the open end of the valve with water or apply soapy water and other similar solutions. Observe the air bubbles to check the leakage between the seat and the seat and the valve body contact surface and the valve seal. It can also be inspected according to the test equipment specified in the order contract, but it should be converted into the unit of leakage specified in Table 4.
b) For multi-channel sealed valves, the test medium shall be introduced with pressure from the sealed passage port in turn, from the packing box (in this case, there should be no packing) or other open passage ports to check the leakage rate of the inlet end sealing surface. . During the test, the leakage rate of each sealing surface shall not exceed the leakage rate specified in Table 4.
Note: For wedge type single gate (rigid or flexible) gate valves , the following test methods are not allowed: such as sealing the test medium on two sealing surfaces, pouring water or applying soapy water on the two sealing surfaces, etc. method.
4.3 For elastomer-sealed butterfly valves, whether one-way or two-way, simply pressurize the test at the end of the most unfavourable seal.
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