Valves are device that controls the flow of a fluid.Valves can even control the rate, volume,pressure and direction of the fluid within the pipe.Valves are not limited to fluids. Valves can turn On/Off, regulate modulate or isolate
Function of valves
Depending upon the usage valves have different functions, some of the basic functions are
1) Opening & Closing to allow the fluid to flow or stop.
2) Throttling the flow of fluid.By opening required valve open percentage throttling of the fluid can be done.Lesser the open percentage higher the throttling.
3) Controlling the flow direction of the fluid.In multiport valves we can decide the direction (way) of flow.
4) Regulating the required pressure and flow within the piping system
5) To safeguard the processing system from over pressure & vacuum conditions pressure and vacuum relief valve are used
CLASSIFICATION OF VALVES
Based on function of Valves
a) Isolation type valves:
Isolates or cuts the fluid flow when required.They are also called as Shutt Off Valves
Eg:- Gate Valve, Ball Valve, Plug Valve, Butterfly Valve
b) Regulation type Valves:
Regulate the flow of fluid depends upon the necessity.These are also called as Control Valves
Eg:-Globe Valve, Needle Valve, Butterfly Valve, Plug Valve
(Globe Valve and Ball Valve both are used as Shutt Off Valve and Control Valve)
c) Safety Relief Valve:
It is used to prevent the over pressure and vaccum inside the processing system to avoid damage of the piping and equipment.
Eg:-Pressure Relief Valve and Vaccum Relief Valve
d) Non-return Valve(NRV)
Prevents back flow within the System.It allows only one direction flow of fluid within the system.
eg:-Swing check Valve, Lift Check Valve
e) Special Purpose Valve:
Some valves are used to serve for multipurpose applications.
Eg:-Multiport Valve(two port, Three port valves), Flush Valve
Based on the type of Motion
a) Linear Motion
Eg:- Gate valve, Globe Valve, Relief Valve etc.
b) Rotary Motion
Eg:- Swing Check Valve, Ball Valve, Butterfly Valve, Plug Valve etc.
c) Quarter turn
Eg:- Ball Valve, Butterfly Valve, Plug Valve etc.
Based on type of End Connections
End Connection means the arrangement or attachment of the valves to the equipment or to the piping.
The types are:
Screwed or Threaded
Flange type end
Wafer type end
Based on Operation
Operated manually with the help of hand wheel or hand lever or gear wheel or chain
b) Power Operation:
Valves are operated by using electric motor or acuator to change and control the valve.
The acutator may be pneumatically, hydrautically or elctrically operated.
c) Automatic Operation:
Here the external power source is not required.The flow of fluid depends upon the fluid pressure to open/close of valve.
Eg:-Check Valve (back flow not possible)
Based on Manufacturing Material
Depends on the environment where the valves are installed and also considering the materials used for construction.Materials used are
Alloy Carbon Steel,
Poly Propylene UHMW-PE,UHMW-HDPE
Body Could be lined with elastomer so that process fluid will not be in contact with the metal.