The Power Behind The Flow: Butterfly Valve Parts Explained

A butterfly valve is a simple quarter-turn valve often used to control or stop the flow of fluids in pipelines. Its few moving parts, low maintenance needs, and easy design make it a practical tool in many industries.

Although butterfly valves come in various types, their core components and functions are essentially the same. The main parts of a butterfly valve include the body, stem, sealing device, upper bearing, lower bearing, bonnet, actuator, seat, and disc. The design of each component may vary depending on the materials used, the fluid medium, and the specific application.

Butterfly Valve Body

The valve body is the outer shell of the butterfly valve, designed to withstand internal pipeline pressure and external mechanical stress while supporting and protecting the internal components.

Butterfly valve bodies are typically installed between two pipeline flanges. The most common body designs are lug-style and wafer-style.

Lug Butterfly Valve

Lug-style bodies feature external threaded holes that match the pipeline flanges, allowing the valve to be bolted securely in place. This design enables one side of the pipeline to be disconnected while the valve remains operational, making it convenient for mid-pipeline installation or replacement without dismantling the entire system.

Wafer Butterfly Valve

Wafer-style butterfly valves are installed by clamping them between two flanges using bolts. Unlike lug-style valves, they do not have separate lugs or threaded connection points. The valve is held in place by the flanges and bolts, simplifying the design and reducing the number of components.

Butterfly Valve Connection Method

Valve Body Material

In the design and selection of valves, various materials are available for the valve body to meet the requirements of different operating conditions. The most commonly used materials for valve bodies include bronze, ductile iron, stainless steel, and plastics.

Butterfly Valve Disc

The valve disc (also called the vane) is one of the key components of a butterfly valve, responsible for regulating and controlling fluid flow. It is a disc-shaped element mounted at the center of the valve body and connected to the actuator via the valve stem. When the stem rotates, the disc turns around its axis, adjusting the valve's opening to control the flow or shut it off.

Butterfly Valve Stem

The valve stem of a butterfly valve is a critical component that connects the disc to the actuator, transferring the actuator's force to the disc to enable opening or closing of the valve.

Valve stems are categorized into two types: single-shaft (integrated) and double-shaft (separated).

Single-shaft stem: The stem and disc are integrated into one piece, directly fixed together through machining and forming.

Double-shaft stem: The upper and lower shafts pass through the valve body to connect with the disc. The stem and disc are secured using keys or pins.

Butterfly Valve Seat

The valve seat of a butterfly valve is a critical sealing component located inside the valve body, surrounding the disc. It works with the disc to create a seal, ensuring no fluid leaks when the valve is closed and providing sufficient sealing support during opening and closing operations.

There are three common types of valve seats: hard seats, soft seats, and vulcanized seats, distinguished mainly by the way the sealing material is integrated with the valve body.

• Hard Seat: Made of rubber on the outside with a rigid backing inside. It is installed by pressing the seat into the valve body using specialized valve assembly equipment.

• Soft Seat: Composed entirely of rubber, offering high elasticity and also referred to as a "backless seat." It can be installed manually, making it easier for workers to replace or repair in the pipeline later.

• Vulcanized Seat: The rubber lining is bonded directly to the valve body, forming a single integrated piece. This type of seat is produced in bulk using large-scale equipment.

Valve seat materials are diverse, including various rubbers, plastics, and metals, chosen based on the application requirements.

Rubber materials: Examples include EPDM, NBR, and VITON, known for their excellent corrosion resistance and elasticity, making them suitable for water and chemical media.

PTFE (Polytetrafluoroethylene): Highly resistant to corrosion and capable of withstanding high temperatures, it is ideal for applications in the chemical industry.

Metal materials: Such as stainless steel and hard alloys, offering high-temperature and high-pressure resistance, are suitable for demanding conditions.Butterfly

Valve Operating Actuator

Based on the actuation method, butterfly valves can be operated manually, or by worm gear, electric, pneumatic, or hydraulic actuators.

• Manual actuator: Operated using a handwheel or handle to directly rotate the valve stem. It may require significant effort for frequent operation of large valves.

• Electric actuator: Powered by electricity, typically using a solenoid valve to drive the stem or a gearbox to convert rotary motion into linear motion.

• Pneumatic actuator: Uses compressed air as an energy source, relying on air pressure differences to generate the force and motion needed to operate the valve.

• Hydraulic actuator: Uses pressurized hydraulic oil to create the required force and motion, making it suitable for large valves or applications with high pressure differentials, often requiring a hydraulic power source.

Criteria for Selecting Butterfly Valve Actuators

• Valve Size: Large-diameter valves typically require pneumatic, hydraulic, or electro-hydraulic actuators to provide sufficient torque.

• Operating Frequency: For high-frequency operations, pneumatic or electric actuators are recommended.

• Control Requirements: Automated systems generally prioritize electric or pneumatic actuators for precise and efficient control.

• Cost-Effectiveness: Overall costs, including purchase, installation, and maintenance expenses, should be carefully evaluated.

As you can see, every component of a butterfly valve plays a crucial role in managing fluid flow effectively across various industrial applications. At TFW, we provide expertly crafted valve bodies, discs, seats, and stems made from high-quality materials to ensure exceptional strength and durability, meeting the demands of even the most challenging operating conditions. Contact our TFW valve supply team to explore customized valve options tailored to your specific operational needs.