A butterfly valve is a type of valve that uses a disc-type opening and closing part (butterfly plate) to rotate back and forth by about 90° to open, close, or regulate the flow of media, and it is an extremely critical component in fluid control systems.
Key Components and Their Roles
Working Principle of Butterfly Valves
The Working Process of Butterfly Valves
Actuation Methods
Connection Methods
FAQ
Keywords: Butterfly Valve, Disc, Principle, Pneumatic, Electric
You can watch the following videos to quickly understand:
Valve Body: The main structure of the valve, which bears fluid pressure and connects to the pipeline.
Disc: The closing part of the valve, disc-shaped like a butterfly wing, which rotates around the center axis to achieve fluid cutoff or throttling.
Stem: The shaft that connects the drive device (such as a handle, worm gear, or actuator) with the disc to transmit torque.
Seat: Located on the inner wall of the valve body to provide a sealing environment, commonly made of rubber (soft seal) or metal (hard seal).
Seal Pair: Composed of the disc sealing ring and the valve seat, this is the "heart" of the valve's sealing performance, ensuring "zero leakage" in the closed state.
A butterfly valve is a 1/4 rotation class valve (Quarter-turn valve). The core principle is controlling fluid continuity or regulating flow by rotating the valve plate (disc) around the valve stem.
Fully Open State: When the stem drives the disc to rotate 90° so the plate surface is parallel to the pipe axis, fluid resistance is minimized. At this time, fluid flows past both sides of the disc.
Fully Closed State: When the plate surface rotates to be perpendicular to the pipe axis, the disc edge contacts the seat tightly under pressure to form a seal, blocking the fluid path.
Regulation State: When the disc stays at any position between 0° and 90°, it can be used as a throttle valve to control flow velocity by changing the opening area.
The rotation of the butterfly valve can be achieved through different execution methods:
Rotation is achieved via a manual handle or worm gear box. Because butterfly valves have large torque under large diameters or high pressure, worm gear reducers are usually used to make operation more labor-saving and control more precise through gear transmission.
This is the most common form in industrial automation. The pneumatic actuator receives air source pressure and converts linear motion into rotational motion through a piston or rack-and-pinion structure.
Action Modes: Divided into single-acting (spring return, automatically closes or opens upon air loss) and double-acting (requires air source to drive both opening and closing).
An electric motor drives a reduction mechanism to rotate the valve stem, suitable for occasions requiring long-distance electrical signal control or where laying air pipes is inconvenient.
Choosing the correct connection method is vital for the stability and sealing of the piping system. The four main connection methods are:
Definition: The valve body does not have flanges on either side; it is clamped between two pipe flanges using long bolts during installation.
Features: This method is the most lightweight, economical, and occupies minimal space. It is suitable for water treatment or air conditioning systems where space is limited and structural weight is a concern.
Definition: The outer edge of the valve body has lugs with threaded holes. Bolts are screwed into the lug holes from both sides to fix the valve to the flanges.
Features: Unlike the wafer type, the lug connection allows for the disassembly of downstream piping without affecting the pressure on the other side (dead-end service), providing greater flexibility and safety for system maintenance.
Definition: The valve body has its own flanges at both ends, which are connected face-to-face with the pipe flanges using bolts.
Features: This is the most traditional and reliable connection method. It has uniform stress on the sealing surface and strong pressure-bearing capacity. Widely used in municipal pipe networks and power plant circulating water systems.
Definition: Both ends of the valve body are processed into welding grooves and welded directly to the pipe ends.
Features: This achieves a "zero leakage" physical connection, eliminating the risk of leakage caused by loose bolts. It is the preferred solution for harsh conditions in the petroleum, chemical, and power industries.
1. Can butterfly valves be used for regulation, or are they limited to on/off control?
Butterfly valves can be used for both on/off control and basic flow control, but they are not suitable for precise regulation.
2. How do the materials/surfaces of industrial and sanitary butterfly valves differ?
Industrial valves use cast iron/carbon steel with a rough surface; sanitary valves use 316L stainless steel with mirror polishing.
3. What is the difference in structure/sealing between industrial and sanitary butterfly valves?
Industrial valves use wafer/flange connections and allow micro-leakage; sanitary valves use clamp quick-loading, have zero dead zones, and utilize FDA-approved seals.
4. Are the cleaning requirements the same for industrial and sanitary butterfly valves?
No. Industrial valves do not require frequent disassembly and washing; sanitary valves must support CIP/SIP and require cleaning validation after each use.
