Butterfly valves are rotary motion valves with a fourth-turn throttling function use to control and regulate the flow through a system. A butterfly valve offers a set of unique advantages including good control, quarter-turn, and openness for diminished plugging systems. Furthermore, butterfly valves can be use in areas with limited space and deliver a high coefficient of flow, making them a significant component of industries today.
As their internal parts are difficult to clean, they are not recommend for use in industries such as medical and food processing, where sterility is a key concern.
Control methods for butterfly valves
Depending on the method of control, butterfly valves control the flow of liquid that passes through them. Often called a vane or butterfly valve, a butterfly valve consists of a circular metal disk. As the disc pivots, the axis of the direction of flow in the pipe is at a right angle.
The circular disc seals itself against the valve seats when the valve is rotate. By offering it a low resistance, the disc permits the flow to pass through.
As butterfly valves must be rotate a quarter turn to close or open a passageway, they operate faster.
Media
It is a characteristic term that describes the material of the system. A disc’s media has a significant impact on what type of material should be use for its construction.
Among the media that pass through the valve system are:
- Solids
When designing a valve for an abrasive or semi-abrasive material application, various factors should be taken into account. The rubber seal of a disc which closes on dry bulk materials is more likely to wear prematurely and to obstruct the orifice the disc creates. Eventually, this may lead to the bridging of the materials at the valve’s inlet.
Additionally, it may even result in the jamming of dry materials or of the disc getting trapped between the disc and the seat, which may, in turn, cause a serious lack of efficiency and, as a result, delay its working and effectiveness.
- Gas
It is highly recommend that valve seals should be tight and in accordance with the system functioning and the specified leakage rate at the given pressure and temperature when dealing with gasses. As the volume is small, it is recommend to use its equal percent characteristics. For large volumes, linear characteristics are recommend if the system pressure drop is greater than 25%.
- Liquid
A system’s seals must be tight in order to prevent leaks and damage. If the calculation exceeds 25% of the pressure drop, it is highly recommend to follow a linear characteristic. By using the parallel percentage characteristic, you can calculate the drop at its maximum flow conditions if it is less than the given percentage.
Butterfly Valve Components
Compared to other valves, the body motion and construction of a butterfly valve are unique.
- Body construction
Butterfly valves have two types of bodies. There are lug and wafer types.
There are protruding legs on the lug shape. In the bolt’s hole, metal inserts are installed. By using separate bolts for each flange, the installation is done between two flanges. It makes way for dead-end service, which is an advantage of this body.
The wafer body type is develop between the flanges using bolts, studs, and nuts. The product doesn’t have protruding legs and is easy to install or replace. It is also cheaper. This has the disadvantage that some valves with this body don’t cast a decent seal and require extra care.
- Valve seat
Butterfly valves are usually seal with disc seals and elastomeric seals. The disc seals adjacent to the diameter of its body, stopping the flow. Depending on the seal’s body, it may be pressed in, locked in, or bonded. Some seals use clamp rings or backing loops to enclose the O-ring extrusion. The seals in some high-performance and durable designs are implemente with interference-fit designs, which are create from the pressure in the pipelines, increasing the interference between the disc and the seat.
Performance Specifications
There are several terms associate with butterfly valves that describe their performance during an operation. Among them are:
- Wetted and non-wetted
The wetted valves are those whose body and stem are expose to the media. A non-wetted valve, on the other hand, keeps its body and stem isolated from the system media.
- Liner and equal percentage flow
During a linear flow, the flow rate is proportional to how far the disc travels. If the disc is 45% open, the flow rate would be 45% of the maximum flow rate. An equal percentage flow, on the other hand, is a flow in which the flow rate is proportional to the change in valve opening.
- Pressure drop
Pressure drop is the difference between the outlet and inlet valves. It is crucial for selecting the appropriate valve size.
Butterfly Valves Applications
Many processes and applications use butterfly valves due to their compatibility with various media types, including corrosive materials, waste treatment, slurries, and water systems. They are also use in:
- Steam and water are dispense at high temperatures and pressures.
- There is a vacuum system.
- There are also slurries and other similar services.
- These include fire protection, gasses, air, and cooling water.
Aira Euro Automation is a leading 3 inch butterfly valve in India. Aira has a wide range of butterfly valves which are operated by a pneumatic actuator, gear & lever.
