Working principle of Butterfly Valve

According to the definition of the British Association of Valves and Actuators, a butterfly valve is "a valve whose orifice rotates at a right angle to the direction of the fluid around an axis. In the open position, the fluid bypasses the valve of the orifice." In other words, the butterfly valve consists of a circle The valve disc or plate is formed in a shape, and the valve stem passes through the middle or is attached in an offset position. When opened, the valve flap rotates 90 degrees in the valve hole, aligns with the fluid, and creates an almost unrestricted flow path. Like the ball valve, the butterfly valve can be quickly closed by rotating 90 degrees. What do we know about it? How does it work? You will find it after reading this article.

The following knowledge points are listed below:

The working principle of butterfly valve

The types of butterfly valve

The application of butterfly valve 

1.The working principle of butterfly valve

It is based on the principle of rapid closure. The valve flap is placed in the center of the pipe, allowing a rod to pass through it to the actuator on the outside of the butterfly valve. The flaps remain parallel or perpendicular to the fluid. Even when the valve is in the open state, the valve flap will produce a pressure drop on the fluid. When the valve flap rotates a quarter turn, the valve flap opens or closes, so it is also called a quarter-turn valve. There is a metal disc on the rod, and when the valve is closed, it blocks the passage by giving it a quarter of the rotation. This metal plate is called a butterfly. It is the most important part of the valve.

2. The types of butterfly valve

The butterfly valve with an elastic seat is the most basic design, and is usually also called a butterfly valve with a concentric or elastic seat. In this type of valve, the valve stem is located at the center of the valve flap, and the valve flap is located at the center of the pipe hole. This kind of valve usually has a rubber (or elastic) valve seat, relying on a valve flap that is in high contact with the valve seat to achieve sealing. During 90-degree rotation, the valve flap first contacts the valve seat (±85 degrees).

The stem of the single offset butterfly valve is located behind the flap. Due to the development of double-bias or high-performance valves, there are very few valves of this type on the market. The single offset of the valve stem makes the valve flap contact with the valve seat, and the remaining moving distance is 3 to 4 degrees; the reason for adopting this design is that it is considered to prolong the service life of the valve because the valve seat has less contact.

The double-offset (high-performance) butterfly valve has two flaps and a rated pressure of 1,480 psi [10 MPa]. Similar to the single-offset design, the double-offset butterfly valve has a valve stem behind the flap. For high-performance butterfly valves, the second offset stem moves again from the center of the flap to one side. This offset geometry causes the 90-degree disc rotation to rub against the valve seat by only 1 to 3 degrees of the 90-degree rotation.

Double offset butterfly valves are used in systems that require higher pressure resistance. The valve flap is located in the center of the pipe hole, and its setting purpose is to improve the sealing ability and reduce the wear on the valve.

3.  The application of butterfly valve

Butterfly valves have long-term, maintenance-free performance and are widely used in various industries, including food and beverage, dry bulk handling, oil and gas drilling and production.

Do you know how the butterfly valve works now?