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A complete Guide of Butterfly Valve Parts and Functions

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The purpose of these valves is to regulate and isolate liquid flow. As a quarter-turn valve, butterfly valves work similarly to ball valves. With just a quarter turn, these valves can move from fully open to fully closed. We’ll explore the different parts of butterfly valves now that we’re familiar with these valves. We are the leading butterfly valve in Zambia. 

  • A butterfly valve body consists of a wafer-shaped body and a leg-shaped butterfly valve.
  • Disk
  • Stem: Wetted, Non-wetted
  • Seat

Other parts can also be included depending on the actuation method, such as:

  • Hand Lever
  • Gear

Depending on the type of butterfly valve, the parts for automatic actuation may differ. Automatic actuation is available in three types: Electric, Pneumatic, and Hydraulic.

A butterfly valve consists of the parts listed above. For a better understanding of their functions, let’s look at them one by one. In order for the butterfly valve to serve its final purpose, each of these parts plays an important role. A rod runs through the disc at the core of the pipe and reaches an actuator on the outside of the valve via the rod runs through the disc. As the actuator rotates, the disc moves. Fluid flow can be perpendicular or parallel to this movement.

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Butterfly Valve Body

Different parts of the butterfly valve are contained within the body. Body designs include wafer-style bodies and lug-style butterfly valves, which fit between two pipe flanges.

  • A Wafer-Style Body

Bolt holes are used to connect the valve to the pipes through the body. Since the wafer-style butterfly valve is easier to install and less complicated than the lug-style butterfly valve, it is more economical. To prevent backflow, they are mainly used in universal flow systems. 

  • Butterfly valves with lugs

For connecting to the pipe, protruding lug holes are placed on the outside of the valve body. Their complex design makes them more expensive than wafer-style bodies. Despite the cost, they have different advantages that justify their purchase. As compared to its competitor, the lug-style butterfly valve is designed in a way that helps carry the weight of piping inside the body. A dead-end valve can be serviced by removing piping from one side.

The disk

Within the body of a butterfly valve, there is a disk that is one of the different parts of the valve. Similar to the gates or balls that are placed inside ball valves, this disk controls the flow of fluid. Additionally, there are two types of disks: Eccentric and Concentric. Eccentric discs have a more complicated design than concentric discs. A stem runs through the centerline of the concentric disk. Low-pressure applications usually use valves with concentric disks. Eccentric disks, on the other hand, have stems that run behind the center line. In the opposite direction, the flow is going.

Eccentric disks are among the parts of butterfly valves that are designed to prevent contact between seals and disks before the butterfly valve is closed. As a result, the valve has a longer lifespan.

Aira Euro Automation is the leading butterfly valve in Zambia. We offer Various types of valves like ball valves, butterfly valves, control valves, plug valves, pressure reducing valves, and many more.

Butterfly Valve


In spite of the stem’s small size compared to the other parts of the butterfly valve, it is crucial for its operation. Stems connect the disk inside the valve to the handle on the outside.

The butterfly valve can be opened or closed with the help of this device.

In terms of stem protection, stems are available in two different designs:

  • Wetted

The design of wetted stems does not contain any materials that protect them against corrosion and erosion. Therefore, it should be made from materials that are compatible with the media flowing through the line.

  • Non-Wetted

As a result of its design, this item is protected from corrosive or erosive liquids.


In addition to the different parts of a butterfly valve, the seat is also important. Most seats are made of polymers and are either pressed, locked down, or bonded to the body. Polymer is used to increase the leak-proof ability of the seal between the seat and disk. As soon as the disk is pressed against the seat, the two will seal together. As a result, the flow will be stopped. It’s interesting to know that the seat runs the entire length of the butterfly valve’s inner diameter.

We are now at the point where we need to consider the actuation method. Depending on the design, butterfly valves can be controlled manually or automatically. Handles and gears are present if they are manual. They contain pneumatic, electric, or hydraulic actuators if they are automatic. The remaining parts of butterfly valves related to these specific designs will now be explained.

Hand Lever

The parts are usually made from steel and are chemically treated and powder coated to ensure their dimensional accuracy after meticulous inspection and salt spray testing. A hand lever usually has a handle and a locking lever. Additionally, they are usually used for small butterfly valves. Locking these hand levers into closed, open, and partially open positions are possible.


For manually operated butterfly valves, the gear is another item on the list of different parts. These valves are used for larger butterfly valves. By using a gearbox, the torque is increased, but the opening and closing speeds are slowed. Butterfly valves with gears are self-locking and cannot be back-driven. However, they may have position indicators.

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