4.7　Inspection of Valves

4.7.1　The following requirements shall be met before valve installation:

1　The switches shall work well and the indications shall be correct.

2　There is no obvious manufacturing defects on the appearance of valves.

3　The inside of valve chest shall be cleaned.The valve sealing surface and flange surface shall be intact and have no burrs or run-through grooves.

4　The actuator and gearing shall be tested and adjusted according to the design requirements.It shall work well and the indications shall be correct.

4.7.2　High pressure valves and valves for transporting inflammable,explosive,poisonous,and harmful medium shall be subjected to 100% leak test.

4.7.3　Not less than 10%(at least one piece)of every lot of the medium and low pressure valves(same manufacturer,same specification,and same type)shall be subjected to leak test.If there are unqualified products,another 20% shall be spot tested.If there are still unqualified products,this lot of valves are forbidden to use.

4.7.4　The methods and requirements of hydraulic leak test for valves shall meet the manufacturer's requirements.If the manufacturer has no requirements,the pressure of leak test is 1.25 times of the design pressure and at least 1.1 times of the valve's maximum allowable working pressure at 20℃.If the maximum working pressure difference marked on valve nameplate or the actuator fitted with the valves are not suitable for the leak test,the test pressure shall be 1.1 times of the maximum working pressure difference marked on valve nameplate.Water shall be introduced from the upward side of valve disc for globe valve leak test.For the gate valve test,the valves shall be closed to check each sealing surface.

4.7.5　Safety valves and the large caliber valves which are not smaller than DN600mm can adopt oil leakage or water seepage method to replace hydrostatic leak test.

4.7.6　Cold condition test report of safety valves shall be provided by the manufacturer.The setting of safety valve in hot condition as well as the valid report shall be carried out and issued by the certified inspector.

4.7.7　Before the leak test of valves,the coating such as the greasing on the joining surface must be cleaned up.

4.7.8　After the acceptance of valve leak test,the water in valve chest shall be totally discharged and marked obviously.The valves shall be tightly plugged temporarily at the end and stored properly according to classification.