Classification Of Valves

（1） Shut-off valve
This type of valve has an opening and closing function. It is permanently installed on the inlet and outlet of cold and heat sources, equipment inlet and outlet, pipeline branch lines (including vertical pipes), and can also be used as a drain valve and a vent valve. Common shut-off valves include gate valves, globe valves, ball valves, and butterfly valves.
Gate valves can be divided into rising and falling stem, single and double gate, wedge gate and parallel gate, etc. Poor sealing of gate valves and difficulty in opening large diameter gate valves; 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.
Globe valves are divided into three types according to the flow direction of the medium: straight through, right angle, and direct flow, with open stem and concealed stem. The shut-off valve has better sealing performance than the gate valve, with a long valve body, high flow resistance, and a maximum nominal diameter of DN200.
The valve core of a ball valve is a round ball with an opening. When the valve stem is moved so that the opening of the ball is facing the pipeline axis, it is fully open, and when turned 90 °, it is fully closed. Ball valves have certain regulating performance and are tightly closed.
The valve core of a butterfly valve is a circular valve plate, which can rotate along the vertical axis of the pipeline. When the valve plate plane is consistent with the pipe axis, it is fully open; When the gate plane is perpendicular to the pipe axis, it is fully closed. Butterfly valves have a small body length, low flow resistance, and higher prices than gate and globe valves.
（2） Check valve
This type of valve is used to prevent media backflow, utilizing the kinetic energy of the fluid itself to open and automatically close when reverse flow occurs. Permanently located at the outlet of the water pump, the outlet of the steam trap, and other places where reverse flow of fluid is not allowed. There are three types of check valves: swing type, lift type, and wafer type. For swing check valves, when fluid can only flow from left to right, it automatically closes when reverse flow occurs. For lift check valves, when the fluid flows from left to right, the valve core is lifted to form a passage, and when the reverse flow occurs, the valve core is pressed onto the valve seat and closed. For wafer check valves, when the fluid flows from left to right, the valve core is opened, forming a passage. When the flow is reversed, 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.
（3） Regulating valve
The pressure difference between the front and rear of the valve is constant. When the opening of a regular valve changes within a large range, its flow rate does not change much, but when it reaches a certain opening, the flow rate changes sharply, indicating poor regulation performance. The regulating valve can change the valve spool stroke according to the direction and size of the signal to change the resistance number of the valve, thereby achieving the purpose of regulating flow. Regulating valves are divided into manual regulating valves and automatic regulating valves, and there are many types of manual or automatic regulating valves, and their regulating performance is also different. Automatic regulating valves include self operated flow regulating valves and self operated differential pressure regulating valves.
（4） Vacuum class
The vacuum category includes vacuum ball valves, vacuum baffle valves, vacuum inflation valves, pneumatic vacuum valves, etc. The vacuum system components used to change the direction of airflow, adjust the flow rate, and cut off or connect pipelines in the vacuum system are called vacuum valves.
（5） Special purpose category
Special purpose categories include pigging valves, vent valves, drain valves, exhaust valves, filters, etc.
Exhaust valves are essential auxiliary components in pipeline systems and are widely used in boilers, air conditioning, oil and gas, and water supply and drainage pipelines. Often installed at commanding heights or bends, etc