Manual cast iron gate valve
Working principle
The gate plate of the wedge gate valve can be made into a whole, called a steel gate plate; it can also be made into a gate plate that can produce slight deformation to improve its craftsmanship and compensate for the deviation of the sealing surface angle during the processing. This kind of The gate is called resilient gate.
Soft seal gate valves are divided into two types: open stem soft seal gate valves and concealed stem soft seal gate valves. Usually there is a trapezoidal thread on the lifting rod. Through the nut in the middle of the gate plate and the guide groove on the valve body, the rotational motion is changed into linear motion, that is, the operating torque is changed into the operating thrust. When the valve is opened, when the lift height of the gate plate is equal to 1:1 times of the valve diameter, the fluid channel is completely unobstructed, but during operation, this position cannot be monitored. In actual use, the top of the valve stem is used as a mark, that is, the position that does not open, as its fully open position. In order to consider the locking phenomenon caused by temperature changes, the valve is usually opened to the top position and then retracted 1/2-1 turn as the fully open valve position. Therefore, the fully open position of the valve is determined by the position of the gate (i.e. stroke). This type of valve should generally be installed horizontally in the pipeline.
Applications
General requirements
1. The specifications and categories of soft seal gate valves should comply with the requirements of the pipeline design documents.
2. The model of the soft seal gate valve should be indicated with the national standard number requirements. If it is an enterprise standard, the relevant description of the model should be indicated.
3. The working pressure of the soft-sealing gate valve is required to be ≥ the working pressure of the pipeline. Without affecting the price, the working pressure that the valve can withstand should be greater than the actual working pressure of the pipeline. Either side of the soft-sealing gate valve should be able to withstand it when it is closed. 1.1 times the valve working pressure without leakage; when the valve is open, the valve body should be able to withstand twice the valve working pressure.
4. The soft seal gate valve manufacturing standard should indicate the national standard number it is based on. If it is an enterprise standard, the enterprise document should be attached to the purchase contract.
Standard quality
1. The valve body material should be mainly cast iron, cast steel, stainless steel, and 316L, and the grade and actual physical and chemical testing data of the cast iron should be indicated.
2. The valve stem material should be made of stainless steel (2CR13). Large-diameter valves should also have stainless steel embedded stems.
3. The nut material is cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than the valve stem.
4. The hardness and strength of the valve stem bushing material should be no greater than that of the valve stem, and it should not cause electrochemical corrosion with the valve stem and valve body when immersed in water.
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