The opening and closing parts of gate valves are gate plates, and the movement direction of the gate plates is perpendicular to the direction of the fluid. The gate valves can only be fully opened and closed, and can not be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used mode gate valves form wedges and wedge angles that vary with the parameters of the valve, usually 50 and 2 52'when the medium is not high. The sluice gate of a wedge valve can be made into a whole, called a rigid gate, or a sluice which can produce a small amount of deformation to improve its craft and make up for the deviation produced by the angle of the sealing surface in the process of processing, which is called an elastic gate.
The type of gate valve can be divided into wedge type gate type gate valve and parallel gate type gate valve according to the close cover configuration, and the wedge type gate type gate valve can be divided into single sluice plate type, double sluice plate type and elastic gate type, and parallel gate type gate valve can be divided into single sluice type and double sluice plate type. According to the screw thread position of the stem, it can be divided into two kinds: the open gate valve and the hidden pole gate valve. When the gate is closed, the sealing surface can be sealed only by the pressure of the medium, that is, the sealing surface of the gate is pressed to the seat of the other side by the pressure of the medium. This is self sealing. Most of the gate valves are forcibly sealed, that is, when the valve is closed, we must rely on external force to force the gate to the valve seat to ensure the sealing performance of the sealing surface.
The gate of the gate valve moves linearly along with the stem. It is called the lift lever gate valve (also known as the gate valve). Usually there are trapezoid threads on the lifting rod. Through the nut at the top of the valve and the guide slot on the valve body, the rotation motion is turned into a straight motion, that is, the operating torque is converted to the operating thrust.
When the valve is opened, when the height of the gate is equal to the 1:1 times of the valve's path, the passage of the fluid is completely unimpeded, but the position is not monitored during operation. The actual use is based on the vertex of the stem as a sign, that is, the location of the open position as its full open position. In order to consider the lock up phenomenon of temperature change, the 1/2 1 circle is usually returned to the top position as the position of the full open valve. Therefore, the full opening position of the valve is determined according to the location of the gate. Some gate valves, valve stem nuts on the gate, hand wheel rotation to drive the stem rotation, and make the gate lift, this valve is called the rotary bar valve or the dark rod valve.
Gate valves have the following advantages
1., the fluid resistance is small, and the sealing surface is eroded and eroded by the medium.
2. open and close is more labor-saving.
3. the flow direction of the medium is not limited, no disturbance is generated, and no pressure is reduced.
4. the shape is simple, the length of the structure is short, the manufacturing process is good, and the application scope is wide.
The shortcomings of the gate valve are as follows:
1. between the sealing surface is easy to cause erosion and abrasion, and maintenance is more difficult.
2. larger size, opening needs a certain space, opening and closing time is long.
The 3. structure is more complex.
Gate valve installation and maintenance should pay attention to the following matters: 1. handwheel, handle and transmission mechanism are not allowed to be used for lifting, and no collision is strictly prohibited. 2. double gate valve should be installed vertically (that is, the valve stem is in a vertical position and the handwheel is at the top). 3. gate valve with bypass valve should be opened before opening valve to balance the pressure difference between inlet and outlet and reduce opening force. 4. gate valve with belt transmission mechanism shall be installed according to the requirements of the product manual. 5. if the valve is frequently switched on, lubricate at least once a month.
The characteristics of elastic seat sealing gate valve: the common gate valve used in the market has been generally leaking or rusting for a long time. The elastic seat seal valve produced by the European high-tech rubber and valve manufacturing technology has been introduced to overcome the defects of the bad seal and rust of the general gate valves, and the elastic sluice gate valve uses the elastic gate to produce micro The compensation effect of the volume elastic deformation achieves a good sealing effect. The valve has the notable advantages of light switch, reliable sealing, good elastic memory and service life.