By function and purpose

（1） Shut off valve

This type of valve is used for opening and closing. It is always used at the inlet and outlet of cold and heat sources, the inlet and outlet of equipment, the branch line of pipeline (including riser), and can also be used as the drain valve and vent valve. 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 ram and double ram, wedge ram and parallel ram, etc. The tightness of the gate valve is poor, and the opening of the large diameter gate valve is difficult; The valve body size is small along the flow direction, the flow resistance is small, and the nominal diameter span of the gate valve is large. According to the flow direction of the medium, the stop valve can be divided into straight type, right angle type and direct flow type, which can be divided into rising stem and non rising stem. The closing tightness of the stop valve is better than that of the gate valve, the valve body is long, the flow resistance is large, and the maximum nominal diameter is DN200. The core of the ball valve is a round ball with an opening. Move the valve rod so that the ball opening is fully open when facing the pipe axis, and turn it 90 ° to fully close. The ball valve has a certain adjustment performance and can be closed tightly. The core of the butterfly valve is a round 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 ram plane is perpendicular to the pipe axis, it is fully closed. The length of butterfly valve body is small, the flow resistance is small, and the price is higher than that of gate valve and globe valve.

（2） Check valve

This type of valve is used to prevent the backflow of media. It can be opened automatically by using the kinetic energy of the fluid itself and closed automatically when reverse flow occurs. It is always used at the outlet of water pump, the outlet of steam trap and other places where reverse flow of fluid is not allowed. Check valves are divided into swing type, lift type and wafer type. For swing check valves, when the fluid can only flow from left to right, it will automatically close when it flows in the opposite direction. For lift check valves, when the fluid flows from left to right, the valve core lifts to form a channel, and 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 channel, and when the reverse flow occurs, 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 back of the valve is fixed. When the opening of an ordinary valve changes in a large range, its flow changes little. When it reaches a certain opening, the flow changes sharply, which means poor regulation performance. The regulating valve can change the resistance number of the valve by changing the stroke of the valve element 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, while the manual or automatic regulating valve is divided into many kinds, and its regulating performance is also different. Automatic regulating valves include self operated flow regulating valve and self operated differential pressure regulating valve.

（4） Vacuum

Vacuum includes vacuum ball valve, vacuum flapper 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 vacuum system elements in the vacuum system, which are called vacuum valves.

（5） Special purpose category

Special purpose categories include pigging valve, vent valve, blowdown valve, vent valve, filter, etc. Exhaust valve is an indispensable auxiliary component in the pipeline system, which is widely used in boilers, air conditioners, oil and gas, water supply and drainage pipelines. It is often installed at the commanding point or elbow to eliminate excess gas in the pipeline, improve the service efficiency of the pipeline and reduce energy consumption.

According to main parameters

According to nominal pressure

(1) Vacuum valve: refers to the valve whose working pressure is lower than the standard atmospheric pressure.

(2) Low pressure valve: refers to the valve with nominal pressure PN ≤ 1.6Mpa.

(3) Medium pressure valve: refers to the valve with nominal pressure PN of 2.5Mpa, 4.0Mpa and 6.4Mpa.

(4) High pressure valve: refers to the valve with the nominal pressure PN of 10.0Mpa~80.0Mpa.

(5) Ultra high pressure valve: refers to the valve with nominal pressure PN ≥ 100.0Mpa.

ccording to operating temperature:

(1) Ultra low temperature valve: used for valves with medium operating temperature t<- 101 ℃.

(2) Normal temperature valve: used for valves with medium operating temperature of - 29 ℃<t<120 ℃.

3) Medium temperature valve: used for valves with medium operating temperature of 120 ℃<t<425 ℃.

(4) High temperature valve: used for valves with medium operating temperature t>425 ℃.

By drive mode:

According to the driving mode, it can be divided into automatic valve, power driven valve and manual valve.

By nominal diameter

(1) Small diameter valve: valve with nominal diameter DN ≤ 40mm.

(2) Medium diameter valve: valve with nominal diameter of 50~300mm.

(3) Large diameter valve: valve with nominal diameter of 350~1200mm.

(4) Extra large diameter valve: valve with nominal diameter DN ≥ 1400mm

According to structural characteristics

The structural characteristics of the valve can be divided into:

(1) Cut off gate shape: the closing piece moves along the center of the valve seat; Such as stop valve

(2) Cock and ball: the closing part is a plunger or ball, which rotates around its centerline; Such as plug valve and ball valve

(3) Gate shape: the closure moves along the center of the vertical valve seat; Such as gate valve, gate, etc

(4) Swing type: the closing piece rotates around the axis outside the valve seat; Such as swing check valve

(5) Butterfly: the disc of the closing piece rotates around the axis in the valve seat; Such as butterfly valve, butterfly check valve, etc

(6) Spool valve shape: the closing element slides in the direction perpendicular to the channel.

By Connection Method

(1) Threaded connection valve: the valve body has internal thread or external thread, which is connected with the pipe thread

(2) Flanged valve: the valve body is equipped with a flange, which is connected with the pipe flange.

(3) Welding connection valve: the valve body is provided with a welding groove, which is welded with the pipeline.

(4) Clamp connected valve: the valve body is provided with a clamp, which is connected with the pipe clamp.

(5) Ferrule connection valve: ferrule is used to connect with the pipeline.

(6) Wafer connection valve: the connection form in which the valve and two end pipes are directly clamped together by bolts.

As per valve body material

(1) Metal material valve: the valve body and other parts are made of metal materials. Such as cast iron valve, cast steel valve, alloy steel valve, copper alloy valve, aluminum alloy valve, lead alloy valve, titanium alloy valve, monel alloy valve, etc.

(2) Non metal material valve: the valve body and other parts are made of non-metallic materials. Such as plastic valve, enamel valve, ceramic valve, glass fiber reinforced plastic valve, etc.