There are Four Types of Butterfly Valves: Wafer, Lug, Double Offset, and Triple Offset

Butterfly valves are quarter-turn rotary motion valves that stop, regulate, and start flow. The butterfly valve is a quick-opening valve. The handle can be rotated 90° to close or open the valve completely. They are used in systems that do not require a positive shut-off. You will learn about the following types of valves in this article.

• Wafer Type

• Lug Style Type

• Flanged Type

• Butt Welded Ends Types

• Zero offset

• Double Offset

• Triple Offset

Butterfly valves with large stems are usually operated with a gearbox-type actuator, which connects the handwheel to the stem. As a result, the operation's speed will be increased and the force will be reduced. It is recommended that this type of valve be installed in the open position.

Wafer Types

Wafer bodies are placed between pipe flanges, and flange bolts surround the valve bodies. Wafer type butterfly valve is easy to install, but they cannot be used as isolation valves.

Lug Style

Bolt holes located in the flanges are guided by protruding lugs that protrude from the periphery of the lug body.

Flanged Type

There is a flange on the body that corresponds to the dimension of the flange on the pipe.

Butt Welded Ends Types

High-pressure services use these types of ends, which are directly welded to the pipe.

Zero offset Butterfly Valve

The valve used in low-pressure and temperature applications has a zero offset design. There is a concentric relationship between the disc axis and the shaft axis in this design. A disc in the open position divides the flow into two halves, with the disc in the middle and parallel to the flow.

There is a resilient seat on this type of valve. The soft seat seals when the disc deforms it. A zero offset valve has the disadvantage of friction between the disk and seat during operation.

Double Offset Butterfly Valve

With Double Offset, the disk is offset from both the valve center line and the valve body center line. This can be seen in the image where one and two are written. As a result, a cam action is created during operation that lifts the seat out of the seal.

As friction applies only during the first few degrees of opening and closing, approximately 10 degrees of opening and closing, double offset makes opening and closing smooth.

Triple Offset Butterfly Valve

A third offset is created by the geometrical design of the seating surface in the Triple Offset design. An offset conical profile is machined into the seat, resulting in a right-angled cone. This can be seen in the third image with a small enlargement of the seating angle.

In this way, frictionless strokes are ensured throughout the operation cycle. A triple offset metal seated valve uses a 90° angle as a mechanical stop at the final point of closure; contact is only made there.

Butterfly Valve Body Parts

Typical butterfly valves have a circular body, round disk, shaft, and metal or soft seats. In the above image, you can see the parts. You can see how the valve works in the video below.

Seat Types

In addition to metal-to-metal seated butterfly valves, soft seated butterfly valves are also available with a fully lined body and disc. In the first image, we see a fully lined, soft, seated disc valve. A soft seat with a metal disk is the second type, while a metal seat with a metal disk is the third.

The butterfly valve disk can be concentric or eccentric with the valve body. As you can see, I have shown three different arrangements of the disk concerning the center of the valve body.

Applications

• There are many different fluid services that Butterfly valves can perform, and they are extremely useful for slurry applications. Their applications include liquids, steam, cryogenics, cooling water, air, gasses, firefighting, and vacuum services.

• All types of industries use butterfly valves, including high-pressure and high-temperature applications.

Advantages

• Due to their compact, lightweight design, Butterfly valves are suitable for large valve applications, as they take up considerably less space than other valves.

• Due to its quick operation, it takes less time to open or close

• In comparison with other valve types, maintenance costs are usually low

• It is rare for a butterfly valve to experience a significant pressure drop

• A valve with a non-metallic seating can be used in corrosive or chemical media.

Disadvantages

• The throttle is limited to services with low differential pressure and disc openings of 30 to 80 degrees.

• As the disk is always in the flow, cavitation and choking are possible. Turbulence flow can also affect disc movement.