Types of Valves
Inroduction
Valves can be classified based on the function. It can for Isolation purposes,
regulation, not return or special purpose.
Also, there are other ways to classify valves, it can be based on their connections,
material, or motion (rotary or linear motion).
Isolation valves:
- Ball Valve
- Gate Valve
- Piston valve
- Diaphragm Valve
- Butterfly valve
Regulation (control) Valves:
- Globe valve
- Needle valve
- Butterfly valve
- Plug Valve
- Pinch Valve
Return Valves:
- Check Valves
Special Valves:
- Multi-port Valve
- Flush bottom valve
- Float valves
- Foot valves
- Line blind Valves
Gate Valve:
A gate valve is the most common type of valve used in any process plant. It is a linear motion valve used to start or stop fluid flow. In service, these valves are either in a fully open or fully closed position. Gate valve cannot be used for throttling or regulation of flow because it’s difficult to control it. Gate valves (GV) are specifically used in isolation applications in many
piping systems.
A pressure drop occurs when there are frictional forces that caused by the resistance to flow. As result, in gate valve there is no resistance and that mean there is a low pressure drop
Ball Valve:
A ball valve is a linear motion valve and that uses a rotary ball to stop and start a flow. A ball valve is usually rotated 90° around its axis to open and close. It is one of the most widely used valve types. Ball Valves are suitable for both liquid and gas services.
- Long service valve
- Low cost
- No lubrication
- Low pressure drops
- Low chance of leakage
- Suitable for Emergency shutdown conditions,
high-pressure service conditions and range of industrial applications.
Globe Valve:
Globe valves are linear motion valves used to start, stop or regulate the flow. They are widely used for throttling and controlling fluid flow.
Globe Valve is used for Flow Control.
Globe valves are typically not used for sizes greater than 12 inch
High Pressure Drop = Need more power = Energy loss Noisy and heavy Globe valve can be used in a wide range of services, both low pressure and high-pressure fluid services Check Valve:
The valve that used to prevent backflow in a piping system is known as a check valve. It is also known
as a non-return valve or NRV Or One Way Valve. When the flow is moving in the proper direction,
the valve remains open. When the flow reverses, the valve closes automatically
Backflow could damage the internal equipment and cause more problems There is no operator in check valve. No stem is required.
An arrow shall be always on check valves to show direction.
Butterfly valve:
Butterfly valve is a quarter motion valve used to start, stop, and regulate the flow.
It can be used to isolate equipment’s with low pressure loss. It used where the space is limited.
Advantages:
- Less maintenance
- Available in large and small dimeter
- Throttling
- Easy to install and remove
- Less space requirement
- Inexpensive
- Easy and fast to open and close
Disadvantages:
- Poor sealing function
- Cavitation may occur
Plug valve:
A plug valve is a quarter turn valve. It is suited for on/off
operation. It’s not normally used for throttling.
Plug valve is economical. Their size is usually small in
comparison to ball valve.
Diaphragm Valve:
Diaphragm valve is bidirectional. They are good at
throttling.
The flow passaged is smooth which results in low pressure drop.
Since Diaphragm valve is good at throttling, they can be used as control valve.
What is the difference between safety valve and relieve valve? (Simply) Safety or relieve valves are used to protect the system against excessive pressure. When there is an excessive pressure, the valve opens and allow the pressure to escape.
Basically, Safety valves are used for steam, air and gases. Relieve valves are generally used for liquids.
Also, there is a SAFTEY RELIEVE valve that can be used both with liquid and gas at the same time.