Checks to be performed before valve installation

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①Carefully check and verify whether the valve model and specifications meet the requirements of the drawings. ②Check whether the valve stem and valve disc open smoothly, and whether there is any sticking or misalignment. ③Check whether the valve is damaged, and whether the threads of the threaded valve are straight and intact. ④Check whether the valve seat is firmly bonded to the valve body, as well as the connections between the valve disc and the valve seat, the valve cover and the valve body, and the valve stem and the valve disc. ⑤Check whether the valve gasket, packing, and fasteners (bolts) are suitable for the requirements of the working medium. ⑥Old or long-idle pressure relief valves should be removed, and debris such as dust and sand must be cleaned off with water. ⑦Remove the access cover and check the sealing degree; the valve disc must close tightly. Pressure testing of valves: Low-pressure, medium-pressure, and high-pressure valves must undergo strength tests and leak-tightness tests. For alloy steel valves, spectral analysis of the casing must be carried out individually to verify the material composition. 1. Strength test of the valve: The strength test of the valve is conducted with the valve in the open position, in order to check for any leaks on the outer surface of the valve. For valves with PN≤32MPa, the test pressure is 1.5 times the nominal pressure, and the test duration must be at least 5 minutes; the valve is considered qualified if there is no leakage at the shell or the packing gland. 2. The tightness test of valves is conducted with the valve fully closed, in order to check for any leaks in the valve’s sealing surfaces. For valves other than butterfly valves, check valves, foot valves, and throttle valves, the test pressure is generally determined based on the nominal pressure; however, when the operating pressure is known, a test pressure of 1.25 times that operating pressure can also be used. The test is considered successful if there are no leaks in the sealing surfaces of the valve disc.