Butterfly valve how does it work

When the valve is fully open, the metal disc or butterfly moves a quarter turn. The passageway is unrestricted allowing fluids or air to pass. In essence, the movement of the disc will depend on whether the valve is open or closed either partially or completely. If the valve is opened partially, it means that the disc will not be rotated a full one quarter turn, thus it cannot provide unrestricted passage.

This means that, smaller amounts of fluid or air will pass through. However, if the valve is opened completely, the disc will be rotated 90 degrees then larger amounts of air or fluid will pass through. There are many other components that form the butterfly valve. They include the resilient seat, body, packing, a stem and an actuator. The resilient seat is mounted on the body of the butterfly valve in order to provide the proper seal.

The seat covers the inner edge of the walls of the valve. It can be made of metal or elastomeric materials. The seat is the primary sealing agent together with the disc. The disc lodges to the seat when the valve is in the closed position. The disc is the thin, waferlike contraption in the middle of the valve. Together with the seat, it seals off the flow of media when the butterfly valve is used for isolation.

For the control of flow, the disc moves to partially open or close, allowing a certain amount to pass through. The stem is what connects the disc to the lever or actuator.

The force from the actuator is passed to the stem to allow the valve to open. The butterfly valve is one of the few industrial valves that are both efficient in isolating and regulating the flow of media. Like most quarter-turn valves, the butterfly valve is also quick to open. The disc is attached to the stem, either through the former or the stem is at the back of the disc.

The stem is attached to the handle that is either placed on top of the body or at its side. Valve operation can be done manually, electronically or pneumatically. If electronically opened, a signal from a remote source tells the gearbox located on top of the valve body to turn the stem so the disc also moves. If pneumatically-driven, a piston is attached to the side of the body.

This will provide the air pressure needed to open the valve. This type of actuation operates the quickest according to many butterfly valve China manufacturers. To open the valve, a handle is turned a quarter-turn. Inside the valve body, the disc changes position from being perpendicular to the flow of the media to being parallel to it. The disc moves away from the seat and towards the centerline of the valve.

If the valve is opened in a full quarter turn, the valve allows the passage of the medium in full force. There is a slight pressure drop when the valve opens.

To close the valve, make another quarter turn in the opposite direction. In this sense, the parallel position of the disc moves to the perpendicular position and as it does, it positions itself to the seats for an even sealing. This is the fully closed position. Throttling happens when the closed valve disc slightly changes position to a certain degree to allow media to pass through but not fully.

The amount of media that can pass through is determined by the angle created by the disc in relation to the valve centerline. Ideally, butterfly valve should be installed in the open position. If the valve was installed in its closed position, there is a good chance that the soft seat will wedge against the disc, making the opening of the valve difficult.

The vast applications and pressure ranges have created different kinds of butterfly valves. It is based on the quick shut off principle. The disc of the valve is placed in the center of the pipe which allows a rod to go through it to an actuator, on the outer side of the valve.

The disc remains parallel or perpendicular to the flow. A pressure drop is introduced by the disc upon the flow even when open. It open or closed when the disc is rotated a quarter turn and hence it is also known as a quarter-turn valve. There is a metal disc on the rod and when the valve is closed it blocks the passageway by giving it a quarter turn. This metal disc is known as a butterfly. It is the most important component of the valve.

Butterfly valves are quick to open type valves used to stop, regulate and start the flow of the fluid. A gearbox type actuator is attached with large butterfly valves and a hand wheel is connected to the stem of the valve via a gearbox.

The butterfly valve is classified into four types. The butterfly valve comes into two designs, centric and eccentric.