Gate valve Overview
Overview of gate valve standard: the opening and closing part of gate valve is gate.
The movement direction of the ram is perpendicular to the direction of the fluid.
The 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 commonly used gate valves are wedge-shaped, and the wedge angle varies with the valve parameters. Wedge gate valve gate can be made into a whole, known as the rigid gate; It can also be made into a ram that can produce a small amount of deformation, so as to improve its processability and make up for the deviation of sealing surface angle in the processing process. This kind of ram is called elastic ram.
Working principle of gate valve: when the gate valve is closed, the sealing surface of flange gate valve can only be sealed by medium pressure, that is, the sealing surface of gate valve is pressed to the valve seat on the other side by medium pressure to ensure the sealing of secret cover, which is self sealing. Most gate valves use forced sealing, that is, when the valve is closed, the gate must be pressed to the seat by external force to ensure the sealing surface. Gate valve gate and stem linear movement, lifting stem gate valve (also known as rising stem gate valve). Generally, there is a trapezoidal thread on the lifting rod, which passes through the nut on the top of the valve and the guide groove on the valve body. The rotary motion becomes linear motion, that is, the operating torque becomes the operating thrust.
When the gate valve is opened:
When the lifting height of the flange gate valve is equal to 1:1 of the valve diameter, the fluid passage will be completely unobstructed, but this position cannot be monitored during operation. In practical use, the apex of the stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the top position, and then returned to 1 / 2-1 circle as the position of full open gate valve. Therefore, the full open position of the valve is determined by the position (i.e. stroke) of the ram. In some gate valves, the stem nut is installed on the gate valve, and the handwheel rotation drives the stem to rotate, so as to lift the gate. This kind of valve is called rotary stem gate valve or Non rising stem gate valve.
Gate valve type: according to the configuration of sealing surface, flange gate valve can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can be further divided into: single gate type, double gate plate type and elastic gate type; Parallel gate valve can be divided into single gate plate and double gate plate. According to the thread position of the stem, it can be divided into two types: rising stem gate valve and Non rising stem gate valve.
Gate valve structure features:
1. Gate valve fluid resistance is small, sealing surface is less media scrubbing and corrosion.
2. The workload of opening and closing is saved.
3. The flow direction of the medium is not limited, it will not interfere with the flow, and it will not reduce the pressure.
4. Simple shape, short structure length, good manufacturing process and wide application range.
Application scope of gate valve: gate valve is widely used in domestic steel plant, petroleum, chemical, natural gas, boiler, paper making, textile, medicine, food, transportation, water supply and drainage, energy, polysilicon, electric power and other industrial pipelines for medium cutting and circulation. Flange gate valve is suitable for pipes with nominal pressure of pn1.6 ~ 6.4Mpa and working temperature of – 29 ~ 600 ℃. It can cut off or connect pipeline medium without adjustment and throttling. The applicable medium of gate valve is water, oil, steam, acid medium, etc.
