List of Valves: 10 Types of Valves
What are Valves in Engineering?
Valves are devices in fluid or gas processing systems used to control, regulate, or direct the flow of the medium by opening and closing pipelines. They can stop or start the flow, vary the amount of flow, control the flow direction, regulate the downstream system or process pressure, and relieve the system when it’s over or under standard pressure.
How Many Valve Types are there?
All of these functions require different types of valves to execute them, and various fluids or gases necessitate further valve variations. Hundreds or even thousands of different types of valves must exist, but they can all be classified into three different groups: Linear Motion, Rotary Motion, and Quarter-Turn Valves.
Let’s take a look in our list of valves and learn about each one, including ball valves, butterfly valves, check valves, diaphragm valves, gate valves, global valves, needle valves, pinch valves, plug valves, and relief valves.
What are the Types of Valves?
The list of valves below offers an introduction to the function and applications of 10 of the most common types of valves.
1. Ball Valves
Ball valves are used for on/off control without loss of pressure, making them ideal for quick closing performance. A 90° turn offers a full closure angle, compared to the multiple turns required for most manual valves.
A ball valve is a rotary motion valve that uses a ball-shaped disc to stop or start flow. When the hole through the ball is in line with the valve body inlet and outlet, the valve opens and fluid passes through. When the hole is perpendicular to the inlet and outlet, the flow is stopped.
2. Butterfly Valves
Butterfly valves provide flow control in large pipe diameters.
A butterfly valve is a rotary motion valve that is used to stop, regulate, and start the flow. Like all 1/4 turn valves, the butterfly valve is fast-acting. The pressure drop across the butterfly valve is very low when the valve is fully open, so butterfly valves are very well-suited for handling large flows of liquids or gases at relatively low pressures.
3. Check Valves
Check valves or non-return valves allow the fluid to pass in one direction.
The check valve is designed to prevent the reversal of flow in a piping system, and it is activated by the flow of material in the pipeline. The pressure of the fluid passing through the system opens the valve, while any reversal of flow will close the valve.
The most common types of check valves are the swing, tilting, piston, and stop valves. They are used in different circumstances, depending upon the system pressure, temperature, and flow requirements. For example, the swing check valve has a relatively low pressure drop, so they are well-suited for medium velocity, high volume flow applications.
4. Diaphragm valve
Diaphragm valves control the flow by moving a diaphragm through the valve using upstream pressure, downstream pressure, or an external source (for example, pneumatic, hydraulic, etc.) to change the position of the diaphragm.
A diaphragm valve is a linear motion type valve that is used to start, regulate, or stop fluid flow. A flexible diaphragm can be raised or lowered onto the valve seat in order to open or close the valve.
One key advantage of diaphragm valves is that only the flexible diaphragm and internal valve flow passages are exposed to the flowing medium. This makes it well-suited for handling corrosive fluids, fibrous slurries, radioactive fluids, or other applications that require contamination-free performance.
5. Gate Valves
Gate valves are mainly used for on/off control in low-pressure drop applications.
Gate valves are linear motion-type valves used to start or stop the flow but are not suitable for regulating flow.
The major advantages of gate valves are a cost-effective, simple design, and very low-pressure drop across the valve when it is fully open. When the valve is fully open, the gate valve’s disc is completely removed from the pipeline’s flow, which allows virtually no resistance.
Related: The Advantages and Disadvantages of Gate Valve
6. Globe Valves
Globe valves are linear motion valves used to stop, start, and regulate fluid flow. They’re ideal for applications that require strict flow regulation.
There are four main globe valve designs: straight flow, angle flow, cross-flow, and Y-flow.
The globe valve generally yields much less seat leakage because the disc to seat ring contact is at right angles, which allows closing the valve tightly. Globe valves are always installed with the system pressure on the underside of the valve seat. This makes it easier to open the valve, and also removes the pressure on the stem, packing, and bonnet when the valve is closed.
The biggest disadvantage of globe valves is that there is a relatively large pressure drop across the valve. In addition, large globe valve sizes require considerable power to operate and are especially noisy in high-pressure applications. Globe valves are also often heavier than other types of valves with the same flow rating.
7. Needle Valves
Needle valves provide precise flow control and flow metering with accurate flow rates of fluids and gases.
Needle valves are used to make relatively fine adjustments in the amount of fluid flow. Its most distinguishing characteristic is the long, tapered needle-like point on the end of the valve’s stem, which acts as a disc. The longer part of the needle is smaller than the orifice in the valve seat and passes through the orifice before the needle seats. This arrangement permits a very gradual increase or decrease in the size of the opening.
Needle valves are usually used as metering valves because the number of turns of the handwheel can be correlated to the amount of flow.
8. Pinch Valves
Pinch valves provide regulation and control of sludge flow, slurries, and fluids with excess suspended solids.
The pinch valve’s simple design renders it a high-value piece of equipment. The pinch control valve consists of a sleeve molded of rubber or other synthetic material and a pinching mechanism. Pinch valves can be used to start, stop, or regulate flow. However, the effective throttling range is usually between 10% and 95% of the rated flow capacity.
Pinch valves are well-suited for handling slurries with large amounts of suspended solids. They can also be used where corrosion or metal contamination of the flow medium might be a problem.
9. Plug Valves
Plug valves are fine valves used for on/off control but with a slight loss of load.
A plug valve is a rotary motion valve used to start or stop flow. It is named by its disc shape, which resembles a plug, and its design is very similar to a ball valve. In the open position, the passage in the plug lines up with the inlet and outlet ports of the valve body. When the plug is turned 90 degrees from the open position, the solid part of the plug blocks the ports and stops the flow. When the plug valve is fully open, there is a very low-pressure drop across the valve.
Plug valves are often used in non-throttling, on-off applications, particularly where the valve must be operated frequently. The valve is also easy to adapt for multiport applications. The use of a multiport valve, depending upon the number of ports in the plug valve, eliminates the need for as many as four conventional shutoff valves, making it a considerable cost and space-saving valve.
10. Relief and Safety Valves
Relief and safety valves prevent equipment damage by relieving accidental system over pressurization.
A relief valve gradually opens as the inlet pressure increases above the setpoint. The valve only opens enough to relieve the overpressure condition, whereas the safety valve rapidly pops fully open as soon as the pressure setting is reached, and it will stay fully open until the pressure drops below a preset pressure.
These valves are very well-suited for opening and closing operations. They can be used to start or stop flow, but are not suitable for regulating flow.
Axial valves use pneumatic or electro-magnetic force to slide the obstructer along an axis. Some examples of these are coaxial valves, and angle seat valves. These valves are typically fast acting and only used for on/off process applications.
Multi-turn rising stem valves move the obstructer by the rotation of a threaded rod (stem) which is attached to the obstructer Examples of multi-turn valves are gate valves, globe valves, pinch valves, diaphragm valves, and needle valves. These valve types are commonly used for flow control applications.
Linear Valves There are 2 distinct types of linear valves: rising stem (multi-turn) and axial. While both valve types rely on the linear motion of the flow obstructer, they are very different in construction and operation.
Rotary Valves (also referred to as “quarter-turn” valves) These types of valves rely on the rotary motion of the flow obstructer In most cases this rotation is limited to 90 degrees (one quarter-turn), however, there are valves that operate using a larger degree of rotation and have more than 2 positions that are used in regular operation. Valves that are truly quarter-turn are completely closed at 0˚ and completely open at 90˚. Examples of quarter-turn valves are ball valves, plug valves, and butterfly valves.
All of the most common types of automated valves fall into one of three main categories. They are linear, rotary, and self-actuated. There are a variety of valve types within each of these categories each having its own benefits. This training course is focused on rotary and linear actuated valves.
A valve is a component in a piping system that is used to control the flow of the media through the system. This control is achieved by the manipulation of some type of obstructer within the valve. Actuated valves use mechanical devices called "actuators" to operate the valve using a power source such as compressed air or electricity. Most actuated valves are also available in a manually operated version, or as an actuated valve with a manual override.
Types of (Quarter-turn) Rotary Valves
Ball Valves
Quarter-turn 2-way ball valves are by far the most common type of process control valve. They are 2-way (inlet and outlet), 2-position (open and closed) valves that are used for shut-off or isolation of a system, or a loop or component within a system. The basic construction of a ball valve includes a ball as the obstructer which is sandwiched between two cup shaped seals referred to as “seats”. Typically the ball has a bore straight through it. Media flows through this bore when the valve is open. When the ball is rotated 90˚, the flow of media is stopped by the sides of the ball which now completely fill the opening in the seats.
3, 4, and even 5-way ball valves are also available, but far less common. These types of ball valves are covered in the lesson on Ball Valves.
Ball Valves are best suited for on/off applications. Throttling is possible, but not an ideal use for most standard ball valves. Specialty ball valves are available for throttling.
Related Links:
- Lesson 6 "Ball Valves"
- Ball Valve Comparison & Selection
Plug Valves
The basic construction of a plug valve is practically identical to that of a ball valve with the exception of the shape of the obstructer used. In this case, the ball is replaced by a slightly tapered cylinder. This cylinder has a bore through it just like a ball valve, and it operates the same way where it is open in one position, and closed when rotated 90˚.
There are advantages to plug valves that make them the preferred choice in certain applications. One is that they contain no voids or cavities in which media can get trapped. Another is that they can be adjusted to fix leaks that may develop over time, where as a ball valve would need to be repaired or replaced.
Like ball valves, plug valves are typically used for on/off applications. Plug valves are often used in extreme service applications such as refineries and chemical plants, where the environment of use is corrosive.
Related Links:
- Lesson 8 "Plug Valves"
- Plug Valve Comparison & Selection
Butterfly Valves
In contrast to ball and plug valves, butterfly valves use a disc shaped obstructer. Basic, general duty butterfly valves are called "resilient seated". They have a single seal ring that acts a a seal between the valve body and disc, as well as the seal between the pipe flanges and valve body. When the disc is perpendicular to the direction of flow, the flow is stopped. When rotated 90˚ the flow goes through the valve by traveling around the slim profile of the disc.
Butterfly valves are commonly used on larger pipe sizes where a ball or plug valve would get very large, expensive, and heavy. Butterfly valves also function rather well as a flow control valve or an on/off valve. If a manual actuator is used in a flow control application, it must lock into place, so that the force of the fluid does not rotate the disc in either direction. Most manual butterfly valves do incorporate this feature.
Related Links:
- Lesson 7 "Butterfly Valves"
- Butterfly Valve Comparison & Selection