Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on / off and pressure control to dish and clothes washers and taps in the home.
Valves are quite diverse and may be classified into a number of basic types. Valves may also be classified by how they are actuated:
- Hydraulic
- Pneumatic
- Manual
- Solenoid valve
- Motor
Valves vary widely in form and application. Size typically range from 0.1 mm to 60 cm. Special valves can have a diameter exceeding 5 meter.
Valves can be categorized into the following basic types:
- Ball Valve: used 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.
- Butterfly valve: used for flow regulation in large pipe diameters.
- Ceramic Disc valve, used mainly in high duty cycle applications or on abrasive fluids. Ceramic disc can also provide Class IV seat leakage
- 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.
- Check Valve or Non-Return Valve: allows the fluid to pass in one direction only.
- 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.
- Control Valves: used to control fluid flow by varying the size of the flow passage
