What is a butterfly valve?

Butterfly valves are very reliable types of valves.
They can be opened or closed by just a quarter turn, but they can also be used to control a flow.

​These properties make a butterfly valve a real "multitasker" that does not require much attention in terms of maintenance.

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What is a butterfly valve?
A butterfly valve is a very compact valve type.
There is a rotatable circular disk mounted in a round housing, which is lined with a sealing material. By rotating the disk 90 degrees, a fully open or closed position is reached. But also positions in between are possible, so that the flow can be regulated.
Butterfly valves are almost always mounted between pipe flanges. There exist butterfly valves with welding ends but such valves are very large in size.​
The position of the lever indicates the position of the disc, so you can visually check if the valve is in the correct position.​

Types of butterfly valves

Ring type butterfly valves
Ring type butterfly valves don't have flanges or other connections, they must be clamped between two pipe flanges. Therefore they are suitable only as inline valve and unsuitable as end valve in a piping system.
An advantage of this type is that they can be rotated in any desired position.​

Mono flange type butterfly valves
This type of butterfly valve is clamped between two pipe flanges when mounted in a piping system. Because the valve is provided with one flange, it is also possible to use it as the end  shut-off valve in a (low pressure) piping system​.

Lug type butterfly valves
This type has tapped holes around the housing. A lug type butterfly valve can be mounted between two pipe flanges, but a function as an end valve in a pipe system is also very suitable.​

Double flange type butterfly valves
Butterfly valves, which are provided with two flanges, are mainly used for larger diameter pipes. This butterfly valves are considerably larger in dimensions than the types of which are described above.​

When are butterfly valves used?

• If a frequent stop and start of flow is needed
• If both throttling services and fully open-close services are required
• If the pipe diameter is larger than the maximum available ball valve diameter
• If a flow needs to be isolated
• If there is little installation space
• If fluids have a high temperature
• Vacuum services

Where are ball valves used?

• Oil and gas industries
• Chemical processes
• Water technologies
• Gas processing
• Shipping
• Food and beverage industries
• Pharmaceutical industries 

Advantages of butterfly valves

• Short installation length
• High flow capacity
• Quick quarter turn on-off operation
• the open or closed position can be checked visually
• Simple construction and only a few parts
• Easy to use
• Long service and low maintenance
• ​Available in a lot of different materials
• High fluid temperatures possible
• Available for gases, liquids and slurries
• Low priced
• Aivailable in large sizes

Disadvantages of butterfly valves

• Higher pressure loss than ball valves in open position
• Limited throttling service (30° - 70° disc opening)
• Cavitation can occur
• High torque required for control
• Difficult to clean​

Materials
Butterfly valves are available in a wide range of materials:

• Steel
• Stainless steel
• Cast Iron
• Plastics: PP, PVC, HDPE

Operation

• Manual
• Pneumatic
• Hydraulic
• Electric

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