The opening and closing member of the dark rod gate valve is a gate. The direction of movement of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully open and fully closed, and cannot be adjusted and throttled. The gate has two sealing faces. The two sealing faces of the most common mode gate valves form a wedge shape. The wedge angle varies with the valve parameters, usually 50, and is 2°52''' when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processability and compensate for the deviation of the sealing surface angle during the machining process. The board is called a resilient shutter.
The dark rod gate valve is also called a rotary rod gate valve (also called a dark rod wedge gate valve). The stem nut is arranged on the gate plate, and the rotation of the hand wheel drives the valve stem to rotate, so that the shutter is lifted, usually has a trapezoidal thread at the bottom end of the valve stem, and the rotary motion is adopted through the thread at the bottom end of the valve and the guide groove on the valve flap. It becomes a linear motion, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lifting height of the gate is equal to 1:1 times the diameter of the valve, the passage of the fluid is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where the valve is opened, as its fully open position. In order to consider the temperature change, the lock phenomenon is usually turned on to the apex position, and then back 1/2~1 turn as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the shutter (ie, stroke).
common enquiries
1.1 The specifications and categories of the dark rod gate valve shall comply with the requirements of the piping design documents.
1.2 The model of the dark rod gate valve should indicate the national standard number requirement. If it is an enterprise standard, the relevant description of the model number should be indicated.
1.3 The working pressure of the dark rod gate valve requires ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the valve should be greater than the actual working pressure of the pipeline; any side under the closed condition of the elastic seat sealing gate should be able to withstand 1.1 times the valve pressure value without leakage; the valve body should be able to withstand twice the valve pressure requirements when the valve is open.
1.4 The manufacturing standard of the dark rod gate valve shall state the national standard number according to the basis. If it is an enterprise standard, the enterprise contract shall be attached to the procurement contract.
Standard
2.1 valve body material, should be spheroidal graphite cast iron, cast steel, stainless steel, 316L, and indicate the actual physical and chemical testing data of the grade and cast iron.
2.2 stem material, stainless steel stem (2CR13), large diameter valve should also be stainless steel embedded valve stem.
2.3 nut material, cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.
2.4 stem bushing material, its hardness and strength should not be greater than the valve stem, and in the water immersion conditions and the valve stem, valve body does not form electrochemical corrosion.
2.5 sealing surface material
1 Elastic seat sealing gate valves are of different types, sealing methods and material requirements are different;
2 ordinary wedge gate valve, the material, fixing method and grinding method of the copper ring should be explained;
3 soft sealing gate valve, physical and chemical testing data of valve plate lining material;
2.6 valve shaft packing
1 Due to the elastic seat sealing gate valve in the pipe network, usually the opening and closing is not frequent, the filler is required to be inactive for several years, the filler is not aging, and the sealing effect is maintained for a long time;
2 The valve shaft packing should also be in good condition when it is subjected to frequent opening and closing;
3 In view of the above requirements, the valve shaft packing is intended to be replaced for a lifetime or not replaced for more than ten years;
4 If the packing needs to be replaced, the design of the pneumatic valve should take into account the measures that can be replaced under water pressure.
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