Gate valve working principle

 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 most common mode gate valves form a wedge shape. The wedge angle varies with the valve parameters, usually 50, and is 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 a small amount of deformation to improve its processability and compensate for the deviation of the sealing surface angle during the machining process. 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 It is single gate type and double gate 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 gate valves are forced to seal, that is, when the valve is closed, the external force is forced to press the gate to the valve seat to ensure the sealing of the sealing surface.
    The gate of the gate valve moves linearly with the valve stem, called the lift gate valve (also called the open gate valve). Usually, trapezoidal threads are provided 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 shutter 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 is usually turned on to the apex position, and then back to 1/2-1 circle as the position of the fully open valve. Therefore, the full open position of the valve is determined according to the position of the gate (ie, stroke). Some gate valves, the stem nut is set on the gate, and the rotation of the hand wheel drives the valve stem to rotate, so that the gate is lifted. It is called a rotary rod gate valve or a dark rod gate valve.
    The gate valve has the following advantages
    1. The fluid resistance is small, and the sealing surface is less brushed and eroded by the medium.
    2. It is more labor-saving to open and close.
    3. The flow direction of the medium is not restricted, and it does not disturb the flow and does not reduce the pressure.
    4. The shape is simple, the structure length is short, the manufacturing process is good, and the application range is wide.
    The disadvantages of the gate valve are as follows:
    1. It is easy to cause erosion and abrasion between sealing surfaces, and maintenance is difficult.
    2. The external dimensions are large, and a certain space is required for opening, and the opening and closing time is long.
    3. The structure is more complicated.
    The installation and maintenance of the gate valve should pay attention to the following items: 1. The handwheel, handle and transmission mechanism 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 product manual. 5. If the valve is used frequently, switch it at least once a month.
    Characteristics of elastic seat sealing gate valve: The general gate valve used in the market has been leaking or rusting for a long time. The company introduced the elastic seat sealing gate valve produced by European high-tech rubber and valve manufacturing technology, which overcomes the bad sealing of the general gate valve. Defects such as rust, the elastic seat sealing gate valve uses the elastic ram to produce a slight elastic deformation compensation effect to achieve a good sealing effect, the valve has the advantages of light switch, reliable sealing, good elastic memory and service life.