General Pressure Test Standards for Valves

This standard adopts the national standard GB/T13927 Pressure Tests of Industrial Valves.

1. Subject content and scope of application
This standard specifies the requirements, methods and evaluation indicators for pressure tests of general valves. This standard applies to the pressure test of gate valves, globe valves, check valves, plug valves, ball valves, butterfly valves, diaphragm valves, etc.
 
2. Terminology
2.1 Test pressure
The gauge pressure born by the inner cavity of the valve during the test

2.2 Shell tests
The pressure test is carried out on the entire valve shell formed by the combination of the valve body and the bonnet. The purpose is to check the tightness of the valve body and bonnet and the pressure resistance of the entire shell, including the joint part between the valve body and the bonnet.

2.3 Sealing tests
A test to check the sealing performance of the opening and closing parts and the valve body's sealing pair.
 
2.4 Upper sealing tests
A test to check the sealing performance of the valve stem and the bonnet's sealing pair.

2.5 Time of duration for tests
It is the duration of the test at the test pressure.
 
3. Test items
The items of the pressure test are as follows:
a. Shell tests
b. Upper sealing tests only for valves with upper sealing structure
c. Seal tests
 
4. Experimental requirements
4.1 Pressure tests should be performed for each valve before leaving the factory.
4.2 Before the completion of the shell test, it is not allowed to paint the valve or use other coatings to prevent leakage, but it is allowed to carry out chemical anti-rust treatment without sealing effect and lining the lining valve. For painted inventory valves, the coating doesn’t need to be removed if the user requests that the pressure test should be redone.
4.3 Before the sealing test, the oil stains on the sealing surface should be removed, but a thin layer of protective agent with a viscosity not greater than kerosene is allowed to be applied. For valves sealed by grease, the grease is allowed to be applied according to the design regulations.
4.4 During the test, the valve should not be subjected to external forces that may affect the test results.
4.5 The temperature of the test medium should be between 5 and 40°C if there is no special requirement.
4.6 The following test media shall be selected by the manufacturer, but shall meet the requirements of Table 1 and Table 2.
a. Liquid: water (rust inhibitor can be added), kerosene or other suitable liquids with a viscosity not greater than kerosene
b. Gas: Air or other suitable gas
4.7 When the liquid is used for the test, the gas in the valve cavity should be discharged. When the gas is used for the test, safety precautions should be taken.
4.8 When the sealing and upper sealing tests are conducted, the valve shall be closed in the way given by the design.
4.9 The test pressure shall meet the requirements.
4.9.1 The test pressure of the shell test shall be as specified in Table 1.
 
Table 1

 
Please note that the maximum allowable working pressure value at 20°C is in accordance with the relevant product standards.
 
4.9.2 The requirements for the test pressure of sealing and upper sealing test should be based on those in Table 2.
 
Table 2

 
4.9.3 The test pressure shall remain unchanged for the duration of the test.
4.10 The duration of the test shall comply with the requirements.
4.10.1 The test duration of the shell test shall not be less than that specified in Table 3.
 
Table 3

 
4.10.2 The test duration of the sealing and upper sealing test shall be not less than that specified in Table 4.
 
Table 4

 
4.10.3 The test duration shall not only meet the requirements of Table 3 and Table 4, but also meet the requirements of the specific leak detection method for the test duration.
 
5. Test methods and steps
The upper sealing test and the shell test should be carried out first, and then the sealing test.

5.1 Upper sealing tests
Close the valve inlet and outlet; loosen the packing gland. If the valve is equipped with an upper seal inspection device, and the performance of the upper seal can be reliably checked without loosening the packing gland, it is not necessary to loosen the packing gland. The valve is in a fully open state; the upper seal is closed, and the body cavity is filled with a test medium. Gradually pressurize to the test pressure, and then check the upper seal performance.

5.2 Shell tests
Close the valve inlet and outlet. Press the packing gland to maintain the test pressure, and the opening and closing parts are partially open. Fill the body cavity with the test medium, and gradually pressurize it to the test pressure. The check valve should be pressurized from the inlet end, and then check the shell, including the stuffing box and the connection between the valve body and the bonnet.

5.3 The pressurization method of the main valves shall comply with that in Table 5. However, ressurization should be performed in the specified flow direction for valves whose flow directions are specified, except for check valves. During the test, the pressure should be gradually increased to the specified test pressure, and then the sealing performance of the sealing pair should be checked.
 
Table 5

 
6. Evaluation indicators
6.1 Shell tests
During the shell test, there should be no visible leakage on the pressure-bearing wall and the connection between the valve body and the bonnet, and there should be no structural damage to the shell (including the stuffing box and the connection between the valve body and the bonnet). If there is no special requirement, leakage at the packing is allowed under the shell test pressure. However, when the test pressure drops to the sealing test pressure, there should be no visible leakage.
 
6.2 Upper sealing tests
There should be no visible leakage for the duration of the test.
 
6.3 Sealing tests
See Table 6 for the requirement for the maximum allowable leakage of the sealing test. The leakage amount in Table 6 is only suitable for the discharge amount to the atmosphere. Grade A is suitable for non-metal elastic sealed valves, and grades B, C and D are suitable for metal sealed valves. Among them, Grade B is suitable for more critical valves, and Grade D is suitable for general valves. The maximum allowable leakage of various types of valves should be in accordance with the relevant product standards. If there are no specific requirements for the relevant standards, the non-metallic elastic sealed valve shall meet the requirements of class A, and the metal sealed valve class D. If Grade B or C is required for the user, it should be specified in the order contract.
 
Table 6