Commonly used media for valve pressure testing include water, oil, air, steam, and nitrogen. Each type of valve has specific methods for strength and tightness testing. Below are detailed procedures for different valve types. (1) **Globe Valve and Throttle Valve** During the strength test, the fully assembled valve is placed in a testing frame. The valve disc is opened, and the medium is injected to the specified pressure. The valve body and cover are inspected for leaks or sweating. For tightness testing, the valve stem must be vertical, and the medium is introduced from the lower end of the disc. After confirming no leakage, the disc is closed, and the other end is checked. If both tests are required, the strength test is done first, followed by the tightness test at reduced pressure. (2) **Gate Valve** The strength test is similar to that of a shut-off valve. For sealing tests, two methods are used: - **Intermediate Pressure Test**: The gate is opened, and pressure is applied. Then, the gate is closed, and the valve is removed to check for leakage on both sides. This method is not suitable for valves with nominal diameters below DN32mm. - **End-to-End Test**: The gate is opened, pressure is applied, and the blind plate is opened to check for leakage. This process is repeated until the test is passed. Before sealing tests, the packing and gasket should be checked. (3) **Ball Valve** For strength testing, the ball should be partially open. - **Floating Ball Valve**: In a half-open position, one end is pressurized, and the other is closed. The ball is rotated, and the sealing performance is checked. The test is repeated from the other side. - **Fixed Ball Valve**: The ball is rotated before closing, and pressure is introduced from one end. The inlet is checked for leaks, and the same is done from the other side. Finally, the valve is half-open, and the inner cavity is filled for inspection. Three-way ball valves require testing at multiple positions. (4) **Plug Valve** - **Strength Test**: The medium is introduced from one end, and other passages are closed. The plug is rotated to fully open positions for testing. - **Sealing Test**: For straight-type plugs, pressure is kept equal in the cavity and passage. The plug is rotated to the closed position, and checks are made from the other end. For multi-port valves, pressure is introduced from the right-angle end while checking from the opposite side. A thin non-acid lubricant may be applied before testing. Gas valves are tested at 1.25 times working pressure. (5) **Butterfly Valve** The strength test is similar to that of a shut-off valve. For sealing tests, the medium is introduced from the flow end, the disc is opened, and the other end is closed. After confirming no leaks, the disc is closed, and the other end is checked. Flow-regulating butterfly valves may not require sealing tests. (6) **Diaphragm Valve** The medium is introduced from either end, and the valve flap is opened. After reaching the test pressure, the valve body and cover are checked for leaks. The pressure is then reduced to the sealing test level, and the flap is closed for further inspection. (7) **Check Valve** In the strength test, the medium is introduced from the inlet, and the other end is closed. No leaks are allowed. For the sealing test, the medium is introduced from the outlet, and the inlet is checked for leaks. (8) **Safety Valve** - **Strength Test**: Water is typically used. The valve is pressurized from the bottom or top, depending on the part being tested. - **Sealing and Constant Pressure Test**: Steam, air, or water is used as the test medium. Safety valves are tested at nominal pressure, with at least two trials. Leaks can be detected using paper or plastic sheets. The constant pressure test requires at least three cycles. For detailed performance testing, refer to GB/T 12242–1989. (9) **Pressure Reducing Valve** - **Strength Test**: The valve is tested after assembly, with a duration of at least 3 minutes for DN150mm and above. Air is used at 1.5 times the maximum pressure. - **Sealing Test**: The test is performed with the actual working medium. Air or water is used at 1.1 times the nominal pressure, while steam is tested at the maximum allowable operating pressure. The difference between inlet and outlet pressure should be at least 0.2MPa. The valve is adjusted to ensure smooth operation. A qualified valve manufacturer must strictly follow industry standards and ensure product quality. This includes rigorous testing and continuous improvement in production processes. Valve Testing Home Page:
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