What are the classifications of valves?

What are the valves according to their functions and 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 the water flow is small, the flow resistance is small, and the nominal diameter span of the gate valve is large.
 Stop 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 and the flow resistance is large. The maximum 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 certain regulating performance and can close more tightly.
The valve core of the butterfly valve is a circular valve plate, which can rotate along the vertical axis vertical 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 reverse flow of the medium. It uses the kinetic energy of the fluid itself to open itself and automatically close when the reverse flow occurs. It is often installed at the outlet of the water pump, the outlet of the steam trap and other places where 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 up 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 against the valve seat and closed. The wafer check valve can be multi-position. 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, its flow rate does not change much. However, when it reaches a certain opening, the flow rate changes sharply, that is, the regulation 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. Regulating valves are divided into manual regulating valves and automatic regulating valves, and manual or automatic regulating valves are divided into many types, and their regulating properties are also different. Automatic regulating valves include self-operated flow regulating valves and self-operated pressure difference regulating valves.
(4) Vacuum type
 The vacuum category includes vacuum ball valves, vacuum baffle valves, vacuum charging valves, pneumatic vacuum valves, etc. Its function is to change the direction of air flow, adjust the amount of air flow, 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.
  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.
  Valve according to main parameters
 According to nominal pressure:
 (1) Vacuum valve: refers to a valve whose working pressure is lower than the standard atmospheric pressure.
  (2) Low-pressure valve: refers to a valve with a nominal pressure PN ≤1.6Mpa.
 (3) Medium pressure valve: refers to valves with nominal pressure PN of 2.5Mpa, 4.0Mpa, and 6.4Mpa.
 (4) High-pressure valve: refers to a valve with a nominal pressure PN of 10.0Mpa~80.0Mpa.
 (5) Ultra-high pressure valve: refers to a valve with a nominal pressure PN≥100.0Mpa.
 Valve according 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 working temperature -29℃<t<120℃.
 (3)Medium temperature valve: used for valves with medium working temperature 120℃<t<425℃.
 (4) High temperature valve: used for valves with medium working temperature t>425℃.
 The driving method of the valve:
 According to the driving method, it can be divided into automatic valves, power-driven valves and manual valves.
 According to nominal diameter
  (1) Small diameter valve: valve with nominal diameter DN≤40mm.
 (2) Medium diameter valve: a valve with a nominal diameter DN of 50~300mm.
  (3) Large diameter valve: a valve with a nominal valve DN of 350~1200mm.
 (4) Extra large diameter valve: valve with nominal diameter DN≥1400mm
ˆValve structural features
The structural characteristics of the valve can be divided into: according to the direction of movement of the closing member relative to the valve seat:
 (1) Interceptor shape: the closing member moves along the center of the valve seat; such as a stop valve
 (2) Plug and ball: The closing member is a plunger or ball, which rotates around its own center line; such as plug valves, ball valves
 (3) Gate shape: the closing member moves along the center of the vertical valve seat; such as gate valves, gates, etc.
 (4) Swing type: the closing member rotates around the axis outside the valve seat; such as swing check valve, etc.
 (5)Butterfly: The disc of the closing member rotates around the axis in the valve seat; such as butterfly valve, butterfly check valve, etc.
  (6) Slide valve type: the closing member slides in the direction perpendicular to the channel. slippery
 Hash the valve according to the connection method
 (1) Threaded connection valve: The valve body has internal threads or external threads, and is connected to the pipe thread..
 (2) Flange connection valve: The valve body is equipped with a flange and is connected to the pipe flange.
 (3) Welded connection valve: The valve body has a welding groove and is welded to the pipe.
 (4) Clamp connection valve: The valve body is equipped with a clamp and is connected to the pipe clamp.
  (5) Cutting sleeve connection valve: It is connected to the pipe using a cutting sleeve.
 (6) Clamp connection valve: a connection form that directly clamps the valve and the pipes at both ends together with bolts.
 By valve body material
 (1) Metal material valve: Its valve body and other parts are made of metal materials. Such as cast iron valves, cast steel valves, alloy steel valves, copper alloy valves, aluminum alloy valves, lead alloy valves, titanium alloy valves, Monel alloy valves, etc.
 (2) Non-metallic material valves: The valve body and other parts are made of non-metallic materials. Such as plastic valves, enamel valves, ceramic valves, fiberglass valves, etc.