Flow direction of Valve – Part 5 ( Butterfly valve )


For this topic, we are introducing about valve direction of various valve types as below:

+ Check valve : Flow direction of Valve – Part 1 (CHECK VALVE)

+ Ball valve: Flow direction of Valve – Part 2 (BALL VALVE)

+ Globe valve: Flow direction of Valve – Part 3 ( Globe valve ) and Flow direction of Valve – Part 4 (GLOBE VALVE) continue

+ Butterfly valve: Flow direction of Valve – Part 5 (BUTTERFLY VALVE)

1.A Butterfly valve is a quarter-turn rotational motion valve, that is used to stop, regulate, and start flow. A butterfly valve has a disc which is mounted on a rotating shaft. When the butterfly valve is fully closed, the disk completely blocks the line. When the butterfly valve is fully opened, the disc is at a right angle to the flow of gas or liquid.

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2.Construction of butterfly valve:

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3.Butterfly Valve components:

The butterfly valve consists of only four main components: body, disk, stem and seat.

  • Butterfly valve body: Butterfly valves generally have bodies that fit between two pipe flanges, the most common being lug and wafer body design.
  • Butterfly valve disk: The disk is how the valve stops flow – it is equivalent to a plug in a plug valve, a gate in a gate valve or a ball in a ball valve. There are variations in disk design and orientation in order to improve flow, sealing and/or operating torque.
  • Butterfly valve Stem: The stem of the butterfly valve may be a one-piece shaft or a two-piece (split-stem) design. The stem in most resilient seated designs is protected from the media, thus allowing an efficient selection of material with respect to cost and mechanical properties.
  • Butterfly valve Seat: The seat of a resilient-seat butterfly valve utilises an interference fit between the disk edge and the seat to provide shutoff. The material of the seat can be made from many different elastomers or polymers. The seat may be bonded to the body or it may be pressed or locked in.

4. Installation: 

A. Valve position:

The valve may be install in any position & offers tightness in both directions. Install the valve in pipe line so that the shaft of valve is horizontal possible. However, it isn’t recommended installing the valve with actuator on the underside because dirt in the pipeline may then enter the body cavity valve and damaged valve packing.

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B. Valve direction:

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The butterfly valves are bi-directional but do have a preferred flow direction. It’s however strongly recommended to install the valves in the preferred flow direction, as it will extend the valve’s life span and will also lower the operating torque.


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