6 Parts of Butterfly Valve + Function

Butterfly valves are considered to be among the quarter-turn valves that are used in pipelines to shut-off flow. It is often said that butterfly valves can be used to regulate the flow. In order to know butterfly more deeply, let's learn about different parts of butterfly valve. There are 6 different Parts of Butterfly Valve:

Butterfly Valve Body: (The wafer-style body, Lug style butterfly valves)

• Disk

• Stem: Wetted, Non-wetted

• Seat

Based on the actuation method, there can be some other parts as well, including:

• Hand Lever

• Gear

The parts mentioned above are the necessary units of a butterfly valve. Now we will explain them one by one to understand their function better.

1. Butterfly Valve Body

The body contains different parts of butterfly valve. Bodies fit between two pipe flanges and they have two common designs: wafer-style body and lug style butterfly valve.

• The Wafer-Style Body

  This design uses bolt holes that run through the body of the valve for connecting to the pipes. The wafer-style body is more economical than the lug style butterfly valve because the design is a bit less complex and it is easier to install. They are mainly used in universal flow systems in order to avoid backflow. Keep in mind that they are not suitable for regulated systems.

• Lug Style Butterfly Valves

  This design uses protruding lug holes that are placed on the outside of the body of the valve for connecting to the pipe. Due to their complex design, they are a bit more expensive compared to wafer-style body design. However, they have different advantages that justify the cost. The valve in lug style butterfly valve has been designed in a way that helps carry the weight of piping inside the body which is a great plus point compared to its competitor. When piping from one side of the valve is removed, you will have dead-end servicing available.

2. Disk

Among different parts of butterfly valve, a disk exists that has been positioned inside the body of the butterfly valve. This disk is responsible to control the flow of the fluid and works similar to the gates or balls that are placed inside the ball valves. The disk also has two types: Eccentric and Concentric. The eccentric disc has a bit more complicated design compared to the concentric. The concentric disk contains a stem that passes through the disk’s centerline. Valves with concentric disks are usually used in applications that require low pressure. The eccentric disk, in contrast, contains a stem that runs behind the center line. It is in the opposite flow direction.

The eccentric disk is among the parts of butterfly valve that has been initially designed to help prevent the contact between the seal and the disk before the butterfly valve is closed completely. This design enables the valve to have a longer lifespan.

3. Stem

Although the stem is a very small item when compared to other parts of butterfly valve, it is crucial for the function of the valve. The stem is used for connecting the disk inside the valve to the handle that is positioned on the outside. It enables the butterfly valve to open or close.

Stems are available with two different designs related to the protection of the stem:

• Wetted

  Wetted stems are vulnerable to corrosion and erosion and don’t contain materials in their design to protect them from such problems. That is why it should be made of materials that are compatible with the media that are going to flow through the line.

• Non-Wetted

  This stem has been designed in a way that is protected from erosive or corrosive liquids that are running in the line.

4. Seat

Last but not least in the list of different parts of butterfly valve is the seat. Seats are usually made from various polymers and are either pressed or locked down or bonded to the body. The use of polymer is to increase the leak-proof ability of the seal between the seat and the disk. By pressing the disk against the seat, these two will seal together. This will stop the flow. It’s interesting to know that the seat runs the length of the inner diameter of the butterfly valve.

Now, this is where the actuation method comes into play. Butterfly valves can be controlled manually or automatically depending on the design. If they are manual, they have handles and gears. If they are automatic, they contain pneumatic, electric, or hydraulic actuators. Now, we’ll explain the remaining parts of butterfly valve that are related to these specific types of designs.

5. Hand Lever

These parts are usually made from steel and they are chemically treated and powder coated to pass meticulous inspection/salt spray tests for dimensional accuracy. Hand levers commonly contain a handle and a locking lever. Plus, they are normally used for small butterfly valves. These hand levers can be locked into different positions including closed, open, and partially open.

6. Gear

Another item in the list of different parts of butterfly valve for the manually operated ones is the gear. They are used for larger butterfly valves. The use of a gearbox increases the torque but slows the opening and closing speed as a result. The butterfly valves that use gears are self-locking and can’t be back driven. But they may have position indicators.

Each of these parts plays an important role in the final purpose of the butterfly valve, if you want know the butterfly valves’ working principle, you should know these 6 parts for first.

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