According to different use requirements, there are many types of control valves, which can be divided into straight stroke and angular stroke according to the way the valve core moves; Diverter three-way control valve, confluence three-way control valve, diaphragm valve, etc.; can be divided into on-off type, integral type and proportional type according to the action law; Close the valve. Only a few commonly used control valves are briefly introduced here.
The straight-through single-seat control valve type has only one valve core and one valve seat in the valve body, simple structure, small leakage (even completely cut off), small allowable pressure difference, suitable for clean media requiring small leakage and small working pressure difference the occasion. In the application, special attention should be paid to the allowable pressure difference to prevent the valve from closing.
The straight-through double-seat control valve has two valve cores and valve seats in the valve body. Because the force of the fluid on the upper and lower spools can cancel each other, the straight-through double-seat control valve has the characteristics of large allowable pressure difference, and the upper and lower spools are not easy to close at the same time, so the leakage is large. It is suitable for clean medium occasions with large pressure difference between both ends of the valve and low leakage requirements, but not suitable for high viscosity and fiber-containing occasions.
The valve body of the angle control valve is a right angle, with a simple flow path and low resistance. It is suitable for the control of high pressure difference, high viscosity, suspended solids and granular substances. Angle control valve is generally suitable for bottom in and side out. At this time, the control valve has good stability. In the case of high pressure difference, in order to prolong the service life of the valve core, side in and bottom out can also be used. However, the side in and the bottom out are prone to shock when the opening is made. Angle valves are also suitable for applications where process piping is right-angle piping.
The valve body of the three-way control valve has three connecting ports, which are suitable for the pipeline control system of the fluid in three directions, and are mostly used for temperature adjustment, ratio adjustment and bypass adjustment of heat exchangers. In use, it should be noted that the fluid temperature difference should not be too large, usually less than 150 °C, otherwise the three-way control valve will be deformed due to large stress, resulting in leakage or damage to the connection. There are two types of three-way control valve: confluence three-way valve and split three-way control valve. The confluent three-way control valve has two input ports for the medium. After flowing in and mixing, it flows out through an outlet; the split three-way control valve is for the medium to flow in from an inlet, and it is divided into two outlets to flow out.