The opening and closing member of the 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 commonly used wedge gate valve form a wedge shape, and the wedge angle varies with the valve parameters. . Wedge gate valve can be made into a whole, called the rigid gate; may be made to produce micro shutter deformation, to improve its process, to compensate for deviation of the angle of the sealing surface is produced in the process, this gate The board is called a resilient shutter.
The types of gate valves can be divided into wedge gate gate valves and parallel gate gate valves according to the sealing surface configuration . The wedge gate gate valves can be further divided into : single gate type, double gate type and elastic gate type; parallel gate type gate valves can be divided into Single ram type and double ram type. According to the thread position of the valve stem, it can be divided into two types: open gate valve and dark gate valve.
When the gate valve is closed , the sealing surface can be sealed only by the medium pressure , that is, the sealing surface of the ram 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. Most of the valve is sealed by force, i.e., the valve is closed, to rely on external force the gate against the valve seat to ensure the tightness of the sealing surface.
The gate of the gate valve moves linearly with the valve stem, which is called the lift gate valve ( also called the open gate valve ) . Usually on the lifter Trapezoidal threads, through the nut at the top of the valve and the guide groove on the valve body, turn the rotary motion into a linear motion , that is, the operating torque becomes the operating thrust.
When the valve is opened, when the lift height of the gate is equal to 1 : 1 of the valve diameter , 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. Temperature appears to consider locking phenomenon, usually open to the vertex position, and then rewind 1/2 - 1 turn, as a fully open position of the valve. Thus, the valve fully open position by the shutter position (i.e., the stroke> determined. Some valve, the valve stem is provided on the shutter, rotation of the hand wheel is rotated to drive the valve stem, the lift gate, such a valve is called Rotary lever gate valve or dark rod gate valve.
The working principle and advantages of the gate valve: turning the hand wheel, through the lifting or lowering of the thread of the hand wheel and the valve stem, the valve plate connected with the valve stem can achieve the function of opening and closing.
The gate valve has the following advantages: the fluid resistance is small , and the sealing surface can be washed and eroded by the medium. Opening and closing is more labor-saving. The flow direction of the medium is not limited , and it does not block the flow and does not reduce the pressure. The utility model has the advantages of simple shape , short structure length, good manufacturing process and wide application range.
The disadvantages of the gate valve are as follows: the erosion between the sealing surfaces is easy to cause erosion and abrasion, and maintenance is difficult. The external dimensions are large, and a certain space is required for opening, and the opening and closing time is long.
The following matters should be noted for the installation and maintenance of the gate valve: 1. Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collision is strictly prohibited. 2. The double gate valve should be installed vertically (ie the stem is in the vertical position and the handwheel is on the top ) . 3. The gate valve with the bypass valve should open the bypass valve before opening (to balance the differential pressure between the inlet and outlet and reduce the opening force ) . 4. The gate valve with transmission mechanism is installed according to the specifications of the product manual.
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