Introduction of Common Valves

1.Gate Valve

Gate valve is the opening and closing body (valve plate) driven by the valve rod, along the sealing surface of the valve seat for lifting movement of the valve, can be connected or stage fluid passage. Gate valve sealing performance is better than the globe valve, fluid resistance is small, opening and closing labour-saving are some of the most commonly used cut-off valves. Disadvantages are large size, complex structure than the globe valve, easy to wear the sealing surface, not easy to repair, generally not suitable for throttling. According to the position of the thread on the gate valve stem is divided into two categories: open stem and concealed stem. The structural characteristics of the gate can be divided into two types of the wedge and parallel type.

2.Stop Valve

The stop valve is suitable for the fluid resistance requirements are not a strict pipeline, that is, the pressure loss is not considered large, as well as high temperature, high-pressure media pipeline or device, for DN <200mm steam and other media pipeline; small valves can be selected globe valve, such as needle valve, instrumentation valve, sampling valve, pressure gauge valve, etc.; globe valve has a flow adjustment or pressure adjustment, but the adjustment accuracy requirements are not high, and the pipeline diameter and For highly toxic media, it is appropriate to use the bellows-sealed globe valve, but the globe valve should not be used for viscous media and media containing particles that are easy to precipitate, but also not for venting valves and low vacuum system valves.

3.Ball Valve

Ball valves are suitable for low temperature, high pressure, high viscosity media. Most ball valves can be used in the media with suspended solid particles, according to the material requirements of the seal can also be used for powder and granular media; full-channel ball valves are not suitable for flow regulation, but suitable for the requirements of fast opening and closing occasions, to facilitate the realization of the accident emergency cut off; usually in the sealing performance is strict, wear, indented channel, opening and closing action quickly, high pressure cut-off (large differential pressure), low noise, the phenomenon of gasification, operation Small torque, fluid resistance in the pipeline, the use of ball valves is recommended.

4.Throttle Valve

Throttle valve other than the valve clack and the valve structure is basically the same, the valve is a throttling parts, different shapes have different characteristics, the valve seat diameter should not be too large, because its opening height is small media flow rate increases, thereby accelerating the erosion of the valve. Throttle valve small size, light weight, good adjustment performance, but the adjustment accuracy is not high.

Throttle valve is suitable for low media temperature, high pressure occasions, suitable for the need to regulate the flow and pressure parts, not suitable for viscosity and solid particles containing media, not suitable for isolation valve.

5. Plug Valve

Plug valve is a valve with a plug body with a through hole as the opening and closing member, and the plug body rotates with the stem to achieve opening and closing. The plug valve has simple structure, rapid opening and closing, easy operation, low fluid resistance, few parts and light weight. Plug valve has straight-through, three-way and four-way type. Straight-through plug valve is used to cut off the medium, three-way and four-way plug valve is used to change the direction of the medium or to divert the medium.Plug valves are suitable for applications requiring fast opening and closing, generally not applicable to steam and higher temperature media, for lower temperature, viscous media, but also for media with suspended particles.

6.Butterfly Valve

Butterfly valve is a butterfly plate rotating 90° around a fixed axis in the valve body to complete the opening and closing action. The butterfly valve is small in size, light in weight and simple in structure, consisting of only a few parts. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop through the valve is very small, so it has good flow control characteristics. The butterfly valve is divided into two sealing types: resilient soft seal and metal hard seal. Resilient seal valve, the seal can be inlaid on the valve body or attached to the butterfly plate periphery, good sealing performance, can be used for both throttling, but also for medium vacuum pipeline and corrosive media. Valves with metal seals generally have longer life than those with resilient seals, but it is difficult to achieve complete sealing, and are usually used for occasions with large changes in flow and pressure drop, and require good throttling performance. Metal seal can be adapted to higher operating temperatures, while the resilient seal has the defect of being limited by temperature.

Butterfly valve is suitable for larger caliber (such as DN>600mm) and short structure length requirements, as well as the need for flow regulation and opening and closing requirements for fast occasions, generally used for temperature ≤ 80 ℃, pressure ≤ 1.0MPa water, oil and compressed air and other media; because butterfly valve compared to the gate valve, ball valve pressure loss is relatively large, so the butterfly valve is suitable for pressure loss requirements are not strict pipeline system.

7.Check Valve

Check valve is a valve that can automatically stop the backflow of fluid. The valve flap of the check valve opens under the action of fluid pressure and fluid flows from the inlet side to the outlet side. When the pressure on the inlet side is lower than that on the outlet side, the flap automatically closes under the action of fluid pressure difference and its own gravity to prevent the backflow of fluid. According to the structure of lift type check valve and swing type check valve. Lift type is better than swing type sealing, fluid resistance. For the pump suction pipe at the suction inlet, it is appropriate to use the bottom valve, its role is: before the pump to fill the pump inlet pipe filled with water; stop the pump to keep the inlet pipe and pump body filled with water, in order to start again. Bottom valve is generally installed only on the vertical pipe of the pump inlet, and the medium flows from the bottom up.

Check valve is generally suitable for clean media, not suitable for media containing solid particles and large viscosity. When ≤ 40mm, it is appropriate to use lift check valve (only allowed to be installed on the horizontal pipeline); when DN = 50 ~ 400mm, it is appropriate to use the swing lift check valve (in the horizontal and vertical pipeline can be installed, such as installed in the vertical pipeline, the media flow from the bottom up); when DN ≥ 450mm, it is appropriate to use the buffer type check valve; when DN = 100 ~ 400mm can also be used Clamp check valve; Swing check valve can be made into a very high working pressure, PN can reach 42MPa, according to the shell and seal material can be applied to any working medium and any working temperature range. The medium is water, steam, gas, corrosive media, oil, drugs, etc. The medium working temperature range is between -196～800℃.

8.Diaphragm Valve

The opening and closing member of the diaphragm valve is a rubber diaphragm, sandwiched between the valve body and the valve cover. The middle protruding part of the diaphragm is fixed on the valve stem, and the valve body is lined with rubber. Since the medium does not enter the inner cavity of the valve cover, the valve stem does not need a stuffing box. Diaphragm valve has simple structure, good sealing performance, easy maintenance, and low fluid resistance. Diaphragm valves are divided into weir type, straight type, right angle type and DC type.

Diaphragm valves are suitable for working temperature less than 200 ℃, pressure less than 1.0MPa oil, water, acidic media and media containing suspended matter, not for organic solvents and strong oxidizing agents media; abrasive granular media should be selected weir type diaphragm valve, select weir type diaphragm valve to refer to its flow characteristics table; viscous fluid, cement slurry and sedimentation media should be selected straight through diaphragm valve; in addition to specific requirements, diaphragm valves should not be used for vacuum pipeline and vacuum equipment.