Butterfly Valve

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 Butterfly Valve:

  • Butterfly valve has a wafer shaped body with a thin rotating disk as the closing device.
  • Like the ball valve, the butterfly valve operates with a one-quarter turn from fully opened to fully close.
  • The disk is always in the flow path, but since it is relatively thin, it offers little restriction to the flow.
  • When the valve is closed, the disk edge fits tightly against a ring shaped linear (Seat).

Working of Butterfly Valve:

Butterfly valves have a relatively simple construction. The main components of a butterfly valve are the body, seal, disc and stem. A typical butterfly valve has the disc positioned in the center of the connected pipe and a stem that is connected to an actuator or handle on the outside of the valve. In the closed position, the disc is perpendicular to the flow, and is sealed by the valve seat. The stem is also sealed by the use of an o-ring. When the actuator or handle rotates the stem back 90 degrees, the disc moves away from the valve seat and positions itself parallel to the flow. Partial rotation allows for the flow to be throttled or proportional.


These Valves generally have one piece bodies that fit sandwich-style between two pipe flanges. The most common body types are Wafer body & Lug body.
  • The wafer body is placed between pipe flanges, and the flange bolts surround the valve body.
  • The lug body has protruding lugs that provide bolts holes matching those in the flanges.

Advantages:

  • An in-built simple and affordable design that comprises of lesser parts which make it maintenance friendly and convenient to repair.
  • Its wafer-form lightweight body makes it budget-friendly as far as the initial price of the valve and installation cost with regard to in-person hours and piping need is concerned.
  • It can transfer mud, with a negligible fluid deposit in the pipeline outlet.
  • They achieve good sealing at low pressure and open and shut easily.
  • Its disc is light-weight when compared to a ball.
  • Butterfly valve needs a much less structural assistance than a ball valve of same diameter needs.

Disadvantages:

  • A certain part of the disc always faces the flow, even when completely opened. The operation of a butterfly valve thus always leads to a pressure switch over the valve irrespective of the setting.
  • It has a poor sealing function.
  • Throttling by employing butterfly valves is restricted to low-pressure drop systems.
  • Possible cavitation and choked flow is a worry when butterfly valves perform.

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