Author:Site Editor Publish Time: 2018-10-03 Origin:Site
Knife gate valve is kind of gate valve,but there is still have difference between gate valve and knife gate valve.The gate valve is a gate of the opening and closing part. 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. Gate valves are classified into slab gate valves and knife gate valves depending on the type of construction.The gate valve is divided into two types: wedge gate valve and parallel gate valve according to the structure of the shutter. Wedge gates are available in three configurations: single wedge, double wedge and resilient wedge.
The gate of the gate valve moves linearly with the valve stem, which is called the lift gate valve, also called the rising stem gate valve. Usually there is a trapezoidal thread on the lifting rod, and the rotary motion is changed into a linear motion by the nut at the top end of the valve and the guide groove on the valve body, 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 occurs, usually at the position of the opening to the apex, and then back to 1/2-1 circle as the position of the fully open valve.
The opening and closing part of the knife-type gate valve is a gate. The direction of movement of the gate is perpendicular to the direction of the fluid. The blade is cut by a blade-shaped shutter that can cut the fiber material. The gate has two sealing faces, and the most commonly used mode gate The two sealing faces of the valve form a wedge shape, the wedge angle varies with the valve parameters, usually 5°, the valve body does not actually have a chamber, the gate plate is lifted and lowered in the side guiding groove, and the lug at the bottom is pressed against the valve.
For high media tightness, an O-ring seat is available for two-way sealing. The knife gate valve has a small installation space, low working pressure, is not easy to accumulate debris, and has a low price.
When the knife gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate is pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing, and most of the gate valves are The use of forced sealing, that is, when the valve is closed, it is necessary to force the ram to the valve seat by external force to ensure the sealing of the sealing surface. This type of valve should generally be installed vertically in the pipeline.