This paper will combine the pressure test standard requirements and step procedures of the famous imported valve brand German Lite LIT valve to analyze the pressure test related problems of the valve.
First, the import valve pressure test requirements:
1. Each valve should be pressure tested before leaving the factory. The famous imported valve brand Germany Lite LIT strictly enforces this standard.
2. It is not allowed to paint the valve or use other leak-preventing coatings before the shell test is completed, but it is allowed to perform chemical anti-rust treatment without sealing and lining the lining valve. For lacquered stock valves, if the user representative asks to redo the pressure test, there is no need to remove the coating.
3. Before the sealing test, the oil stain on the sealing surface should be removed, but it is allowed to apply a thin layer of protective agent with a viscosity no greater than kerosene. The grease-sealed valve allows the application of grease selected according to the design specifications.
4. The valve should not be subjected to external forces that may affect the test results during the test.
5. Unless otherwise specified, the temperature of the test medium should be between 5 and 40 °C. However, in some valves that require high temperature media conditions, it is also possible to use a medium for test sealing.
6. The following test media are selected by the manufacturer, but should meet the requirements of Tables 1 and 2; a liquid: water (can be added with rust inhibitor), kerosene or other suitable liquid with viscosity not greater than; b gas: air or other Suitable gas.
7. When testing with liquid, the gas in the valve chamber should be excluded. Safety measures should be taken when testing with gas.
8. When performing the sealing and upper sealing tests, it shall be closed in the manner given by the design.
9. The test pressure should be in accordance with the regulations.
Second, the inlet valve pressure test method and steps should first carry out the upper seal test and shell test, then carry out the seal test on the seal test to close the valve inlet and outlet, and relax the packing gland (if the valve is equipped with an upper seal inspection device, and not When the packing gland is relaxed, the performance of the upper seal can be reliably checked, and the packing gland is not required to be loosened. The valve is fully open, the upper seal is closed, the body cavity is filled with the test medium, and the pressure is gradually pressurized to the test pressure, and then Check the upper sealing performance 2, the shell test closes the valve inlet and outlet, presses the packing gland to maintain the test pressure, and the opening and closing member is 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 inspect the housing (including the stuffing box and the valve body and bonnet joint).
3. Understanding of the terminology of the relevant pressure test pressure The test pressure is divided into two types: the shell test pressure and the seal test pressure. The pressure specified when the valve is tested in the housing is referred to as the excess dispensing test pressure. The pressure specified when the valve is subjected to the seal test is called the seal test pressure.
The "Test and Inspection of Valves" standard states:
1. The test pressure of the shell is 1.5 times the nominal pressure at 38 °C. For example, Germany Lite LIT's nominal pressure 1.6Mpa imported ball valve, its shell test pressure is 2.4Mpa, 2.5Mpa inlet shut-off valve, its shell test pressure is 3.75Mpa
2. The high pressure seal test and the high pressure upper seal test pressure are 1.1 times the nominal pressure at 38 °C. For example, Germany Lite LIT's nominal pressure 1.6Mpa imported gate valve, imported solenoid valve, his high pressure seal test and high pressure upper seal test pressure is 1.76Mpa
3. The low pressure seal test and the low pressure upper seal test pressure are 0.5~0.7MPa.
4. The sealing test pressure of the butterfly valve is 1.1 times the rated pressure difference.
5. The sealing test pressure of the check valve is the nominal pressure at 38 °C.
The specific pressure test methods for different types of valves are analyzed next.
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