What to Consider in Choosing Butterfly Valves

Butterfly valves

Butterfly valves control the flow of fluid by a quarter-turn rotation motion. These valves are used with various types of media. Butterfly valves are highly remarkable as they have several advantages to offer to people. Aside from their quarter-turn motion, they also have excellent control capabilities and compatible with various chemical processes.

Butterfly valves can be widely used in several applications as they are used in areas with limited space. They are preferably used for high-temperature and high-pressure water and steam services. If you are thinking of buying butterfly valves or a swivel flange, there are a lot of things that you need to consider.

1.  Body style

One of the things to take into account is the body style of the butterfly valves that you plan to purchase. The body styles of butterfly valves depend mostly on the location of the valve in the piping system.

Some valves are located in the middle of a process line, which is sandwiched between two bolted flanges that are passing through the valve. These butterfly valves have a wafer body style. Wafer style butterfly valves are not threaded in the valve body.

Lug style butterfly valves, on the other hand, have lugs in the body to provide passage for the bolt holes. These bolts match the ones found in the flanges. Lug style butterfly valves can remove one mating flange. The threaded metal lugs that are inserted can be over-molded in the valve body. Or the lug can be inserted in a valve body, which is molded to be capable of accepting a lug.

2.  Materials

Butterfly valves are made from various materials. They can either be nonmetallic or metallic. In choosing the material for, you will have to consider the environment where it operates, its media, and its lifespan.

The most common material for valves is carbon steel since they are readily available, affordable, and have high resistance to heat. However, carbon steel is not corrosion-resistant. Another material used for valves in stainless steel. Compared to carbon steel, stainless steel butterfly valves have tensile strength and are resistant to high temperatures and corrosion. Stainless steel may be a bit costly than carbon steel materials.

However, when the applications require extreme levels of pressure and corrosion, special alloys are used in the construction of valves.

Plastic is also commonly used by various industries. The ones that are available in the market are polyvinyl chloride (PVC) butterfly valves and chlorinated polyvinyl chloride (CPVC)  valves.

3.  Types of Butterfly Valve

Butterfly valves come in various types, and they are based on the design of the seat and disc. These types are concentric, double eccentric, or triple eccentric valves.

Concentric valves have the center of rotation located at the centerline of the valve disc. The design of concentric valves depends on the friction interference seal between the seat and the seal. These concentric butterfly valves are conically designed and on center, which are ideal for soft seated valves.

Known as high-performance valves, double eccentric butterfly valves have a continuous circular sealing surface. The disc’s sealing plane is offset from the rotation’s axis, which prevents jamming when opening or closing the valve. A double eccentric butterfly removes weak points around the disc, which makes the valve free from leakage.

Triple eccentric valves have a remarkable conical sealing principle with the help of a metal sheet attached to them. Triple eccentric, as the name implies, has three offsets to the design. Each offset ensures that the valve is sealed tightly to withstand extreme pressure drops and temperature fluctuations.

4.  Type of Media

Before making the big decision of purchasing valves, you need to determine why do you need these valves for. Knowing the type of media that you will be using can help you figure out what type of valves do you need.

Media is a term for describing the material that goes inside the piping system. The media has an important role to play as you select the valve that you need and the material to be used in the construction of the disc. The types of media that could be in the valve system are gases, solids, or liquid.

Valves needed for gas systems require a minimum specified rate of leakage in a particular operating pressure and temperature. Valves used for liquid applications should have tight seals to prevent the possibility of experiencing leakage problems. When dealing with solid media, a lot of considerations should be taken into account, especially to avoid jamming and encountering obstruction in the process.

Conclusion

Butterfly valves are designed to be used in various applications. They are widely used in fire protection, vacuum, and cooling water systems. They are also applicable to highly corrosive processes. And by this, it is essential to choose the right valves for your needs.

Different types of valves are found in the market. You may opt to choose double flanged butterfly valves or high-performance valves with high-pressure and high-temperature applications.