A valve is a device that shuts off, regulates/throttles, prevents, relieves, directs or control the flow of a fluids by opening, closing, or partially obstructing various passageways. In an open valve, fluid flows in a direction from higher pressure to lower pressure.
A strainer, also called Y-strainer or basket strainer, are devices for mechanically removing unwanted solids from fluid lines by means of a perforated or wire mesh straining element.
The general classification of valves according to their functions are:
1. Gate Valve - typically designed to be fully opened or closed.
2. Globe Valve – for throttling applications and has positive shut off.
3. Check Valve – for preventing backflow or stops flow from reversing.
4. Ball Valve - for on/off, throttling and balancing services, and has positive & bubble tight shut off.
5. Butterfly Valve – for on/off and regulating/throttling services, and has positive shut off.
6. Relief Valve – also called Pressure Relief Valves, is a type of safety valve used to control or limit the pressure in a vessel or system to prevent equipment failure and catastrophic incidents.
7. Pressure Reducing Valve – for reducing the input pressure of a fluid to a desired or controlled value at its output.
8. Strainers – for preventing clogged fluid lines to protect pumps, control valves, traps, meters and other devices.