This kind of valve is used for opening and closing. It can also be used as drain valve and vent valve on cold and heat source inlet and outlet, equipment inlet and outlet, pipeline branch line (including riser). Common shut-off valves include gate valve, globe valve, ball valve and butterfly valve.
Gate valves can be divided into rising stem and Non rising stem, single gate and double gate, wedge gate and parallel gate, etc. The closing tightness of gate valve is not good, and it is difficult to open large-diameter gate valve; The valve body size along the water flow direction is small, the flow resistance is small, and the nominal diameter span of the gate valve is large.
According to the medium flow direction, the stop valve is divided into straight through type, right angle type and direct flow type, including exposed rod and concealed rod. The closing tightness of the stop valve is better than that of the gate valve. The valve body is long and the flow resistance is large. The maximum nominal diameter is DN200.
The valve core of the ball valve is a round ball with an opening. Move the valve rod to make the opening of the ball face the axis of the pipe to be fully open, and turn 90 ° to be fully closed. The ball valve has certain regulation performance and is tightly closed.
The valve core of the butterfly valve is a circular valve plate, which can rotate along the vertical axis perpendicular to the pipeline axis. When the valve plate plane is consistent with the pipe axis, it is fully open; When the plane of the ram is perpendicular to the pipe axis, it is fully closed. Butterfly valve body length is small, the flow resistance is small, and the price is higher than that of gate valve and stop valve[ 1]
2. Check valve
This kind of valve is used to prevent medium backflow, open it by using the kinetic energy of the fluid itself, and close it automatically in case of reverse flow. Standing at the outlet of the water pump, the outlet of the steam trap and other places where the reverse flow of fluid is not allowed. Check valves are divided into swing type, lifting type and wafer type. For swing check valves, the fluid can only flow from left to right, and automatically closes in reverse flow. For the lift check valve, when the fluid flows from left to right, the valve core is lifted to form a path. When the fluid flows in the opposite direction, the valve core is pressed onto the valve seat and closed. For the wafer check valve, when the fluid flows from left to right, the valve core is opened to form a path. When the fluid flows in the opposite direction, the valve core is pressed onto the valve seat and closed. The wafer check valve can be installed in multiple positions, with small volume, light weight and compact structure[ 1]
3. Regulating valve
The pressure difference before and after the valve is certain. When the opening of an ordinary valve changes in a large range, the flow changes little, but when it reaches a certain opening, the flow changes sharply, that is, the regulation performance is poor. The regulating valve can change the resistance number of the valve by changing the spool stroke according to the direction and size of the signal, so as to achieve the purpose of regulating the flow. The regulating valve is divided into manual regulating valve and automatic regulating valve, and the manual or automatic regulating valve is divided into many kinds, and its regulating performance is also different. Automatic control valves include self operated flow control valve and self operated differential pressure control valve[ 1]
4. Vacuum class
Vacuum class includes vacuum ball valve, vacuum baffle valve, vacuum charging valve, pneumatic vacuum valve, etc. Its function is to change the air flow direction, adjust the air flow, and cut off or connect the pipeline in the vacuum system, which is called vacuum valve.
5.Special purpose class
Special purpose categories include pigging valve, vent valve, blowdown valve, exhaust valve, filter, etc.
Exhaust valve is an essential auxiliary component in pipeline system, which is widely used in boiler, air conditioning, oil and gas, water supply and drainage pipeline. It is often installed at the commanding point or elbow to eliminate excess gas in the pipeline, improve the use efficiency of pipeline roads and reduce energy consumption.
