The Valve Has Reliable Sealing Performance

The sealing performance of the valve refers to the ability of each sealing part of the valve to prevent the leakage of the medium, which is the most important technical performance index of the valve. There are three sealing parts of the valve: the contact between the opening and closing parts and the two sealing surfaces of the valve seat; the cooperation between the packing and the valve stem and the stuffing box; the connection between the valve body and the valve cover. The leakage in the former part is called internal leakage, which is commonly referred to as lax closure, which will affect the ability of the valve to cut off the medium. For shut-off valves, internal leakage is not allowed. The leakage in the latter two places is called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve. External leakage will cause material loss, pollute the environment, and even cause accidents in severe cases. For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

When a valve is manufactured in batches of a certain specification, an official agency should be entrusted to carry out the following performance tests: ① the opening and closing torque of the valve under the condition of industrial pressure; ② the detection of the flow resistance coefficient of the valve under the condition of pipeline water delivery.

The valve should be tested as follows before leaving the factory: ① When the valve is open, the valve body should withstand the internal pressure test of twice the working pressure value of the valve; ② When the valve is closed, both sides bear 11 times the working pressure value of the valve, respectively. There is no leakage; however, the leakage value of metal-sealed butterfly valves is not greater than the relevant requirements.

Valve Specification Requirements

1. The model of the valve should indicate the requirements of the national standard number. If it is an enterprise standard, the relevant description of the model should be indicated.

2. The working pressure of the valve is required to be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline.

3. The valve manufacturing standard should indicate the national standard number based on it. If it is an enterprise standard, the enterprise document should be attached to the purchase contract.