Valves Types and Operation
Valves are quite diverse and may be classified into a number types.
1. Ball valve, for on/off control without pressure drop, and ideal for quick shut-off, since a 90° turn offers complete shut-off angle, compared to multiple turns required on most manual valves.
2. Butterfly valve, for flow regulation in large pipe diameters.
3. Ceramic Disc valve, used mainly in high duty cycle applications or on abrasive fluids. Ceramic disc can also provide Class IV seat leakage
4. Clapper valve, Used in appliances like the Siamese fire appliance to allow only 1 hose to connected instead of two (the clapper valve blocks the other side from leaking out.
5. Check valve or non-return valve, allows the fluid to pass in one direction only.
6. Choke valve, a valve that raises or lowers a solid cylinder which is placed around or inside another cylinder which has holes or slots. Used for high pressure drops found in oil and gas wellheads.
7. Diaphragm valve, which controls flow by a movement of a diaphragm. Upstream pressure, downstream pressure, or an external source (e.g., pneumatic, hydraulic, etc.) can be used to change the position of the diaphragm.
8. Gate valve, mainly for on/off control, with low pressure drop.
9. Globe valve, good for regulating flow.
10. Knife valve, similar to a gate valve, but usually more compact. Often used for slurries or powders on/off control.
11. Needle valve for accurate flow control.
12. Pinch valve, for slurry flow regulation and control.
13. Piston valve, for regulating fluids that carry solids in suspension.
14. Plug valve, slim valve for on/off control but with some pressure drop.
15. Poppet valve, commonly used in piston engines to regulate the fuel mixture intake and exhaust
16. Spool valve, for hydraulic control
17. Thermal expansion valve, used in refrigeration and air conditioning systems.
18. Pressure Reducing Valve
19. Sampling valves
20. Safety valve
