Butterfly valve are low-pressure valves of efficient design which are used to control and regulate flow. They are characterized by fast operation and low pressure drop. They require only a quarter-turn from closed to full open position. Butterfly valve are available with metal-to-metal seats, soft seats and with fully lined body and disk. The soft seats permit bubble-tight shut off and the full lining enhances erosion and corrosion resistance.
Butterfly Valves consists of a disc that rotates on a shaft at right angles to the fluid flow. When open, the disc is edge-on to the flow and the fluid passes around it, offering limited resistance. In the closed position, the disc is rotated against a seat in the body of the valve.
Butterfly valve usually take up little more room than a pair of pipe flanges, and are therefore an attractive alternative to the ball valve where space is limited. In fact, some butterfly valves are designed specifically for insertion between pipe flanges, these are known as wafer butterfly valves.
Butterfly valves are commonly used as control valves in applications where the pressure drops required of the valves are relatively low. Butterfly valves can be used in applications as either shutoff valves (on/off service) or as throttling valves (for flow or pressure control). As shutoff valves, butterfly valves offer excellent performance within the range of their pressure rating.
Typical uses would include isolation of equipment, fill/drain systems, bypass systems, and other like applications where the only criteria for control of the flow/pressure is that it be on or off. Although butterfly valves have only a limited ability to control pressure or flow, they have been widely used as control valves because of the economics involved. The control capabilities of a butterfly valve can also be significantly improved by coupling it with an operator and electronic control package.
Butterfly valves allow high flows with relatively low pressure loss from the valves, and are typically used for flow control for valve openings from 30 to 70 degrees of full open. At valve openings greater than 70 degrees, the pressure loss of a butterfly valve is too low to produce any significant effect on flow or the energy loss of a flow system.
Two special applications for a butterfly valve include the use of a valve for free discharge and the use of a butterfly valve for flashing or choking cavitation service. Free discharge typically produces high pipe velocities at moderate pressure drops, and choking cavitation typically produces high velocities with large pressure drops. The following paper also includes a review of flow coefficients and the application of non-line sized valves, or valves installed in larger diameter pipes with the aid of pipe reducers.
Types of butterfly valve
There are many different types of butterfly valves, but they can be broadly classified into three main categories:
Body type: Butterfly valves can be either wafer or lug. Wafer valves have a thin body that can be sandwiched between two flanges, while lug valves have a thicker body with lugs that bolt directly to the flanges.
Disc type: Butterfly valves can have either metal or resilient discs. Metal discs are more durable and can withstand higher pressures, while resilient discs are more forgiving and can be used with a wider range of fluids.
Offset type: Butterfly valves can be zero-offset, double-offset, or triple-offset. The offset of a butterfly valve refers to the distance between the center of the disc and the center of the valve stem. Zero-offset valves have no offset, while double-offset valves have an offset that is twice the thickness of the disc. Triple-offset valves have an offset that is three times the thickness of the disc.
Butterfly valves seat materials
- Bune N
How does a butterfly valve work
A butterfly valves is a quarter-turn valve that is used to control the flow of fluids. The valve is named for the disc-shaped valve member that resembles a butterfly’s wings. The disc is connected to a rod that is rotated by a handwheel, gearmotor, pneumatic actuator, or electric actuator. When the disc is rotated 90 degrees, it changes from a closed position to an open position, or vice versa.
The disc of a butterfly valves is typically made of metal or a resilient material such as rubber or plastic. The metal discs are more durable and can withstand higher pressures, while the resilient discs are more forgiving and can be used with a wider range of fluids.
The body of a butterfly valves is typically made of steel, stainless steel, brass, or plastic. The material of the body is chosen based on the application and the fluid that will be flowing through the valve.
Butterfly valves are a versatile type of valve that can be used in a wide variety of applications. They are relatively inexpensive and easy to install, which makes them a popular choice for many industries.
Here are the steps on how a butterfly valves works:
- The valve is in the closed position. The disc is rotated 90 degrees so that it is perpendicular to the flow of fluid.
- The valve is opened. The disc is rotated another 90 degrees so that it is parallel to the flow of fluid.
- The valve is in the open position. The disc is now allowing the fluid to flow through the valve.
The amount of flow through a butterfly valve is controlled by the position of the disc. When the disc is fully open, the valve is allowing the maximum amount of flow. When the disc is fully closed, the valve is preventing any flow.
Butterfly valves are a type of quarter-turn valve, which means that they can be fully opened or closed with a single rotation of the disc. This makes them a fast-acting type of valve that is well-suited for applications where rapid flow control is required.