There are many types of valves, and each type of valve has its own advantages and roles. Selecting the incorrect valve may make control of a pipeline project difficult or even impossible, so it is vital to select the right valve.
1. Gate valve selection
In general, gate valves should be preferred. Gate valves are suitable for steam, oil and other media, but also for media containing granular solids and viscosity, and for venting and low vacuum system valves. For media with solid particles, the gate valve body should be with one or two blow holes. For low-temperature media, should be used for low-temperature special gate valve.
2. Globe valve selection instructions
Globe valve is suitable for the fluid resistance requirements of the pipeline is not strict, that is, the pressure loss is not a big consideration, as well as high temperature, high pressure media pipeline or device, suitable for DN <200mm steam and other media pipeline; small valves can be used to select the globe valve, such as needle valves, instrumentation valves, sampling valves, manometer valves and so on;
Globe valve flow regulation or pressure regulation, but the regulation of precision requirements are not high, and the pipeline diameter is relatively small, it is appropriate to use the globe valve or throttle; for highly toxic media, it is appropriate to use the bellows sealed globe valve; but the globe valve should not be used for viscosity of the medium and contain particles easy to precipitate media, and should not be used as a bleeder valve and the valve of the low-vacuum system.
3. Ball valve selection instructions
Ball valves are suitable for low temperature, high pressure, viscosity of the medium.
Most ball valves can be used in the medium with suspended solid particles, according to the material requirements of the seal can also be used for powdery and granular media; full-channel ball valves are not suitable for flow regulation, but for the requirements of rapid opening and closing occasions, to facilitate the realization of the accident emergency cut off; usually in the sealing performance is strict, wear and tear, indentation of the channel, open and close quickly, high-pressure cut-off (differential pressure), low noise, gasification phenomenon, the operating torque is small, the fluid resistance. Torque is small, small fluid resistance in the pipeline, the recommended use of ball valves; ball valves are suitable for lightweight structure, low-pressure cut-off, corrosive media;
Ball valve or low temperature, deep cold media, the most ideal valve, low-temperature media piping systems and devices, it is appropriate to choose to add the bonnet of the low-temperature ball valves; selection of floating ball ball valve seat material should be to undertake the ball and the load of the working medium, large calibre ball valves in the operation of the need for greater force, DN ≥ 200mm ball valves should be selected in the form of a worm gear drive;
Fixed ball valve is suitable for larger calibre and higher pressure occasions; in addition, used for the process of highly toxic materials, flammable media pipeline ball valves, should have fire prevention, anti-static structure.
4. Throttle valve selection instructions
Throttle valve is suitable for medium temperature is low, high pressure occasions, suitable for the need to regulate the flow and pressure of the parts, not for viscosity and solid particles in the medium, should not be used as a disconnecting valve.
5. Plug valve selection instructions
Plug valves are suitable for occasions requiring rapid opening and closing, generally not suitable for steam and higher temperature media, for lower temperature, viscosity of the medium, but also for the medium with suspended particles.
6. Butterfly valve selection instructions
Butterfly valve is suitable for large calibre (such as DN>600mm) and short structure length requirements, as well as the need for flow regulation and opening and closing requirements for rapid occasions, generally used for temperature ≤ 80 ℃, pressure ≤ 1.0MPa water, oil and compressed air and other media; due to the butterfly valve relative to the gate valve, the ball valve pressure loss is relatively large, the butterfly valve is suitable for pressure loss requirements are not stringent pipeline system.
7. Check valve selection instructions
Check valve is generally applicable to clean media, should not be used for solid particles and viscosity of the medium. When DN ≤ 40mm, it is appropriate to use lift check valve (only allowed to be installed in the horizontal pipeline);
When DN = 50 ~ 400mm, it is appropriate to use the rotary lift check valve (in the horizontal and vertical pipeline can be installed, such as installation in the vertical pipeline, the media flow direction should be from the bottom up);
When DN ≥ 450mm, it is appropriate to use buffer type check valve;
When DN = 100 ~ 400mm can also be used for the clamped check valve; Swing check valve can be made into a very high working pressure, PN can reach 42MPa, according to the shell and seals of different materials can be applied to any working medium and any working temperature range.
The medium is water, steam, gas, corrosive media, oil, pharmaceuticals and so on. The working temperature range of medium is between -196～800℃.
8. Diaphragm valve selection instructions
Diaphragm valve is suitable for working temperature less than 200 ℃, pressure less than 1.0MPa oil, water, acidic media and media containing suspended solids, not for organic solvents and strong oxidants media; abrasive particulate media should be selected weir diaphragm valves, the selection of weir diaphragm valves to refer to its flow characteristics table;
Viscous fluid, cement slurry and precipitating media should be selected through the diaphragm valve; in addition to specific requirements, the diaphragm valve should not be used for vacuum piping and vacuum equipment.
