How should we choose gate valve?
To choose a gate valve, we first need to know what our gate valve does and what its purpose is. This is beneficial for us to choose a gate valve.
What are the classifications of gate valve?
Rising stem gate valve
The opening and closing part of the Rising stem gate valve is a gate, and the moving direction of the gate is perpendicular to the direction of the fluid. The Rising stem gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled.
The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valve form a wedge. The wedge angle varies with valve parameters, usually 50, and 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 slight deformation to improve its manufacturability and make up for the deviation of the sealing surface angle during the processing. The plate is called an elastic gate.
The types of rising stem gate valve can be divided into wedge gate valve and parallel gate valve according to the sealing surface configuration. Wedge gate valve can be divided into: single gate type, double gate type and elastic gate type; parallel gate type Gate valves can be divided into single gate type and double gate type.
Installation and maintenance of Rising stem gate valve
Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collisions are strictly prohibited.
The double gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
Gate valves with bypass valves should be opened before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism should be installed according to the product manual.
If the valve is frequently opened and closed, lubricate at least once a month.
NON-Rising stem gate valve
NON-Rising stem gate valve is also called rotating stem gate valve (also called dark stem wedge gate valve). The valve stem nut is set on the gate, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. Usually there is a trapezoidal thread at the bottom end of the valve stem. The thread on the bottom end of the valve and the guide groove on the disc will rotate It becomes linear motion, that is, the operating torque is changed to operating thrust.
Internal and external anti-corrosion of NON-Rising stem gate valve
The inside and outside of the valve body (including the variable speed transmission box) should be shot blasted to remove rust, and strive to electrostatically spray powdered non-toxic epoxy resin with a thickness of more than 0.3mm. When it is difficult to electrostatic spray non-toxic epoxy resin for extra-large valves, similar non-toxic epoxy paint should be brushed or sprayed.
The inside of the valve body and the various parts of the valve plate require comprehensive anti-corrosion. On the one hand, it will not rust when immersed in water, and there will be no electrochemical corrosion between the two metals; on the other hand, the surface is smooth to reduce the water resistance.
The sanitary requirements of the anticorrosive epoxy resin or paint in the valve body shall have the inspection report of the corresponding authority. The chemical and physical properties should also meet relevant requirements.
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