Valves can be divided into shut-off valves, check valves, regulating valves, vacuum valves, and special-purpose valves according to their uses.
(1) Shut-off valve
This type of valve has the function of opening and closing. It is often installed on the inlet and outlet of cold and heat sources, the inlet and outlet of equipment, and branch lines of pipelines (including risers). It can also be used as a water release valve and an air release valve. Common shut-off valves include gate valves, globe valves, ball valves, and butterfly valves. Gate valves can be divided into open stems and concealed stems, single gates and double gates, wedge gates and parallel gates, etc. The closing tightness of the gate valve is not good, and it is difficult to open the large-diameter gate valve; the size of the valve body along the direction of water flow is small, the flow resistance is small, and the nominal diameter span of the gate valve is large. Globe valves are divided into three types according to the flow direction of the medium: straight-through type, right-angle type, and direct-flow type, with open stem and concealed stem. The closing tightness of the globe valve is better than that of the gate valve. The valve body is long, the flow resistance is large, and the nominal diameter is DN200. The valve core of the ball valve is a round ball with a hole. The plate moves the valve stem so that the ball opening is fully open when it is facing the axis of the pipeline, and it is fully closed when it is turned 90°. The ball valve has a certain adjustment performance and can close tightly. The valve core of the butterfly valve is a circular valve plate, which can rotate along the vertical axis perpendicular to the axis of the pipeline. When the valve plate plane is consistent with the pipe axis, it is fully open; when the gate plate plane is perpendicular to the pipe axis, it is fully closed. Butterfly valve body length is small, flow resistance is small, and it is more expensive than gate valves and globe valves.
(2) Check valve
This type of valve is used to prevent the medium from flowing back, using the kinetic energy of the fluid itself to open itself and automatically close when the flow reverses. It is often installed 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 three types: swing type, lift type, and wafer type. For swing check valves, when fluid can only flow from left to right, it will automatically close when flowing in the opposite direction. For the lift check valve, when the fluid flows from left to right, the valve core lifts to form a passage. When the fluid flows in the reverse direction, the valve core is pressed against 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 passage. When the fluid flows in the reverse direction, the valve core is pressed to the valve seat and closed. The wafer check valve can be multi-positioned. Easy to install, small in size, light in weight, and compact in structure.
(3) Regulating valve
The pressure difference between the front and rear of the valve is constant. When the opening of an ordinary valve changes within a wide range, the flow rate does not change much. However, when it reaches a certain opening, the flow rate changes sharply, that is, the regulating performance is poor. The regulating valve can change the valve core stroke according to the direction and size of the signal to change the resistance number of the valve, thereby achieving the purpose of regulating the flow rate of the valve.
(4) Vacuum type
Vacuum categories include vacuum ball valves, vacuum baffle valves, vacuum charging valves, pneumatic vacuum valves, etc. Its function is to change the direction of airflow, adjust the amount of airflow, and cut off or connect the pipeline in the vacuum system. The vacuum system component is called a vacuum valve.
(5) Special-purpose categories
Special purpose categories include pigging valves, vent valves, blowdown valves, exhaust valves, filters, etc. The exhaust valve is an essential auxiliary component in the pipeline system and is widely used in boilers, air conditioners, oil and gas, water supply, and drainage pipelines. It is often installed at commanding heights or elbows to eliminate excess gas in pipelines, improve pipeline efficiency, and reduce energy consumption.
Post time: Oct-17-2023