Flanged Butterfly Valve

What is a flanged butterfly valve? 

This is a butterfly valve that is designed with flanges on both inlet and outlet faces. A flange is a flat surface that makes a connection between a valve and the pipe very easy and free from leakage.

Butterfly valve flange type has its flanges with holes. The pipe end to be connected to the valve is also designed with a flange and holes of the same size as those on the flanged valve. The valve is secured on the piping system using bolts and nuts. Flanged butterfly valve manufacturers design these valves for flawless and hassle-free performance. These valves are extensively meant for use in heavy-duty applications as they can endure a tough and harsh environment. This valve is meant for shut-off and throttling applications. The working of this valve is based on a quarter turn of the valve closing element which opens and closes fluid flow as necessary. This type of valve can be operated manually or through actuators. 

Figure: Flanged butterfly valve.

Components of a flanged butterfly valve

Handwheel/actuator 

This component provides the power needed to start and stop the valve. The handwheel or hand lever is used in manual valves. The valve operator applies force to open and close the valve on the hand lever or handwheel. The actuator is used in automatic and semi-automatic valves and it provides the power needed to operate the valve as well as an automation system that determines when to open and close the fluid flow. 

Body 

This is the main part of a butterfly valve flange type that is used to house and support all other parts. Other parts of the valve find their support from the body. As such, flanged butterfly valve manufacturer design the body from strong metallic materials like carbon steel and stainless steel to ensure the valve body is strong enough against the weight of other parts and high fluid pressure. The body also protects internal parts against damage from falling objects. 

Stem 

This is the component of a flanged butterfly valve that connects the disc and the handwheel. The stem is a shaft that transmits rotary force applied on the handwheel to the disc so that fluid flow can be started or stopped as necessary. 

Disc 

This is the closing element of a flanged butterfly valve thus it ensures no fluid flow when the valve is closed. The disc gets rotary force from the handwheel via the stem. 

Seat 

This is a soft or metallic material placed between the disc and the body to prevent fluid leakage when the valve is closed. The seat serves as the seating surface where the disc rests on once the valve is closed. Flanged butterfly valve manufacturer produce the seat from different materials depending on the operating temperature and type of media the valve will be used on. 

Packing 

This is a sealing material placed between the stem and the valve body to prevent fluid leakage as well as dust and dirt from entering the valve. 

Gasket 

This is a component placed between the valve and pipe flanged surfaces. It helps to prevent fluid leakage by ensuring a tight seal. 

Figure: Components of a flanged butterfly valve.

How does a flanged butterfly valve work? 

A flanged butterfly valve is a quarter-turn valve. This means that the valve disc is rotated for a quarter turn to start or stop fluid flow. To open a butterfly valve flange type, the hand lever or handwheel is rotated in the anticlockwise direction for a quarter turn (90^o degrees). This rotary motion on the handwheel is transmitted to the valve disc. As such, the valve disc is forced to remain collinear to the pipe. This forces the disc to create an unobstructed path for the fluid flow. To close a flanged butterfly valve, the handwheel is then rotated for a quarter turn in the opposite (clockwise) direction to when it was being opened. This forces the disc to turn in the opposite direction where it aligns itself perpendicular to the pipe. As such, it blocks any fluid attempting to cross through the valve. To use this valve for throttling, the handwheel is turned slightly for an angle of less than 90^o degrees. This allows some amount of fluid to flow through the valve. Flanged butterfly valve manufacturers recommend the use of this valve for throttling application only if the pressure drop is low so as not to interfere with fluid reaching the target destination. 

Figure: Working of a flanged butterfly valve.

Types of flanged butterfly valves 

Manual flanged butterfly valve 

This is a flanged butterfly valve that is operated using a handwheel or hand lever. Flanged butterfly valve manufacturers design some of these valves with a gear system. The gear system is used to help in changing the direction of torque from horizontal to vertical. The handwheel is designed to be horizontal and perpendicular to the stem. As such, flanged butterfly valve manufacturers use the gear system to convert torque along the horizontal axis so that it can be along the vertical axis. The gear system also helps to multiply the torque applied by the valve operator to make it easy to open and close the valve. Manual flanged butterfly valves are cheaper compared to the automatic or the semi-automatic types. These valves are more versatile to use as they are used where electricity or another source of power is not available. Also, manual flanged butterfly valves can be automated if the user finds it necessary to. However, if the valve torque is high or valve operations become too frequent, the valve operator will be so tired. 

Figure: Manual butterfly valve flange type (handwheel and hand lever types).

Actuated flanged butterfly valves 

This is the category of flanged butterfly valves that are operated using an actuator. The actuator is the source of power that makes the valve open and close. Flanged butterfly valve manufacturer design these valves so that they can be remote controlled and also be able to determine when to open and close the fluid flow. The automation system comes with the actuator used. These actuated flanged butterfly valves are much safer compared to the manual ones especially when the valve is operating on hazardous and high-pressure fluids since any leakage can cause injuries to the operator. Also, these valves reduce the cost of having valve operators. Three types of actuators can be used on these valves which include pneumatic, electric and hydraulic actuators. 

Figure: Actuated butterfly valve flange type.

Double offset flanged butterfly valve 

This is a valve that has the stem axis being offset behind the seat centerline and the body. The stem is again offset from the valve vertical centerline. This brings the total number of offsets to two thus the name “double offset” flanged butterfly valve. Flanged butterfly valve manufacturers design this valve such that when the valve is opened, the seat lifts from the seal which helps to reduce friction when the disc makes the first and last ten degrees of the valve start and stop respectively. This design makes the valve very smooth in operation and has better sealing features and consequently long service life compared to other valves with zero offset. Flanged butterfly valve manufacturers design this valve with soft seats. Due to the soft seats, these double offset butterfly valves are suitable for use in low-temperature below 60 ^oC. These valves are used in various applications such as water purification, wastewater treatment, fire protection, heating ventilation and air conditioning (HVAC) among others. 

Figure: Double offset butterfly valve flange type.

Triple offset flanged butterfly valve 

This is a flanged butterfly valve that has three offsets. These valve has the first two offsets as the double type and the third offset is an angular body sealing cone. This third offset comes with a right-angled cone profile of the valve seat. This offset helps to eliminate the disc and seat contact during the start and stop of the valve which then eliminates friction. Contact occurs only when the valve is fully closed and this acts as a stop to ensure the disc does not rotate further. Flanged butterfly valve manufacturers design this type of valve with metallic seats. Metallic seats are more rigid and tougher relative to the soft seats. As such, these seats withstand high temperatures and high pressure. These features help reduce wear. Triple offset flanged butterfly valves have long service life compared to the double offset types.

Figure: Triple offset butterfly valve flange type.

Applications of flanged butterfly valves 

• S team power plants. 
• They are used in mining. 
• Food and beverage processing plants because they are easy to clean. 
• These valves are also used in the manufacturing of pharmaceutical products since they can be cleaned to enhance high levels of hygiene. 
• Municipal water supply and wastewater treatment. 
• Fire protection. 
• Manufacturing of paper and pulp. 
• They are used in the refinery of petroleum products. 
• Manufacturing of different chemicals. 
• SS butterfly valves are used in HVAC systems.

Advantages of flanged butterfly valves 

• These valves can be operated manually or automatically. 
• Small in size and light in weight compared to gate valve, check valve and globe valve. 
• They are of compact and simple design. 
• Can be used in both high-pressure and high-temperature applications depending on the valve seat material. 
• Free from fluid leakage. 
• They can be installed where space is limited, unlike other large-sized valves. 
• Shut-off and throttling fluid flow applications. 
• These valves operate by making a quarter turn which makes their operations very fast. 
• Easy to install, clean, and repair. 

Disadvantages of flanged butterfly valves 

• These valves have poor sealing features compared to other valves like ball valve. 
• Suitable for use in throttling applications if pressured drop is low.
• The valve disc remains in the fluid path when the valve is open which increases the chances of pressure drop and thus low efficiency. 

Troubleshooting flanged butterfly valves 

Valve is hard to operate 

• Clogged materials inside the valve. Open the valve and remove such materials. 
• Corroded internal parts. Open the valve and clean off any corrosion. 

Internal fluid leakage 

• Damaged seats. Replace the valve seats. 
• Worn out O-rings. Replace the O-rings. 
• Dirt in the valve. Open the valve and clean the dirt.

External fluid leakage 

• High fluid pressure. Ensure the valve is working at the pressure level recommended by the flange butterfly valve manufacturer. 
• Loose bolts. Tighten the bolts to the torque required by the flanged butterfly valve manufacturer.
• Worn out gasket. Replace the gasket. 
• Worn out packing. Replace the packing. 

Summary 

A flanged butterfly valve is a valve with flanges at the inlet and outlets sides. The flanges have holes used to secure bolts when connecting the valve to the pipe. A gasket is placed between the valve and pipe to enhance a tight seal.

Flanged butterfly valve manufacturers produce these valves from different materials for use in different applications. These valves operate by turning the disc for a quarter turn to start and stop fluid flow. The operation of the valve can be manual or it can be done using valve actuators. Butterfly valve flange types are stronger when compared to other types of butterfly valves.