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Butterfly Valve

What is a butterfly valve?

A butterfly valve is a device that allows and blocks fluid passage in a pipe by rotating a disc a quarter turn. Butterfly valves are quarter-turn valves.

Table of Contents

Butterfly valve principle

Butterfly valves connect the disc and handle with a metal rod. When the direction of the disc is parallel to the direction of fluid flow, the valve is in the open position and fluid is allowed to pass. When the disk is rotated a quarter turn, the disk is perpendicular to the direction of fluid flow, the valve is closed, and the fluid is prohibited from passing through.

Butterfly Valve Parts Name

The butterfly valve has a compact structure and simple design. The flow of fluid is controlled by the rotation of the valve disc. Figure 1 shows the main components of a butterfly valve, namely the valve body, seal, valve disc and valve stem.

Handle/driving mechanism: The operating mechanism of the butterfly valve. The connecting handle is connected to the valve disc through the valve stem, and the rotation and closing of the valve  disc are controlled through the operating mechanism. In order to improve the flow rate or operating torque, there are 4 categories of butterfly valve operating mechanisms. There are 4 types of operating mechanisms for butterfly valves, handle type, hand wheel type, pneumatic device, hydraulic device, etc.

Valve disc: Connected to the handle or operating mechanism through the valve stem, its function is to prevent or allow fluid to pass through the valve. When the valve disc rotates a quarter turn, parallel to the direction of fluid flow, fluid can pass through the butterfly valve. When the valve disc is perpendicular to the flow direction, the valve is closed.

Sealing gasket:The seal exists between the valve disc and the valve body to ensure the valve’s long-term sealing. In order to adapt to different fluids, the sealing ring material can be selected according to the fluid medium.

Valve stem: The valve stem, also commonly called the valve shaft, is the component that connects the valve disc to the actuator and transmits torque through itself. Usually the valve stem material is stainless steel.

Valve body: The valve body acts as a shell to accommodate internal parts and is installed between the pipe flanges to provide a leak-proof connection with the pipe. Common plastic butterfly valve body materials include: PVC, CPVC, PPH, FRPP.

PVC Butterfly Valve Part

PVC Butterfly Valve Part

A: Actuator B: Disc C: Seals D:Stem E: Valve body

Butterfly valve actuation

According to different butterfly valve operating mechanisms, there are four common types of butterfly valve operating mechanisms: handle type, worm gear type, pneumatic actuator, and electric actuator.

Handle-type:Handle-type butterfly valves usually have a self-locking mechanism that can be used to adjust flow. The self-locking mechanism can also strengthen the closing state of the valve and prevent the valve from being flushed open by the fluid when it is not completely closed. Hold the handle to open the self-locking mechanism, rotate the handle, and the valve is in the open state. The handle type butterfly valve is suitable for small size butterfly valves, which open and close quickly and require large torque.

The worm gear type : worm gear type uses a gear transmission mechanism to link the valve stem to rotate. The opening speed is slow and labor-saving.

Pneumatic actuator: The compressed air drives the gear to link the valve stem to drive the valve disc to rotate. Pneumatic actuator has slow opening and closing speed and is suitable for large-sized valves and pipeline systems with a high degree of automation.

Electric actuator: Through the partial rotation electric actuator, the valve disc is controlled to rotate to achieve the open and closed state. The main advantages of electric actuators are a high degree of stability and constant thrust that the user can apply.



Lug style PVC Handle Butterfly Valve

PVC Handle Butterfly Valve

PVC Gear Butterfly Valve

PVC Gear Butterfly Valve

UPVC Pneumatic Butterfly Valve

UPVC Pneumatic Butterfly Valve

CPVC Electric Butterfly Valve

CPVC Electric Butterfly Valve

What is the advantage of a butterfly valve?

Lightweight and Compact: Butterfly valves have a compact body and the disc is connected directly to the actuator, taking up less space than other valve types. These valves can be installed in pipelines in confined spaces.

Cost Effective: Butterfly valves are very simple in design and require minimal maintenance. They are easy to install and operate.

Fast and efficient: The 90-degree turning radius allows for quick sealing when driven, opening and closing the valve in a short time.

Modular design: The butterfly valve sealing ring material and operating mechanism can be selected according to the chemical properties of the fluid medium.

Regulating Flow: In a piping system system, a specific pipe flow must be maintained. Butterfly valves can adjust the flow in the pipeline according to the opening angle.

Low maintenance costs: The butterfly valve has few internal parts and a simple structure, which ensures little component interference, thereby reducing failures.


What is a Butterfly Valve Used For?

Butterfly valves are available in a variety of body and seal material options, making them suitable for a variety of uses in municipal water supply, sewage treatment, industry, HVAC systems, slurry and other fields.

How Are Butterfly Valves Installed?

When installing butterfly valves, you should follow the operating instructions. Correct installation can extend the life of the valve and reduce maintenance.

  1. Determine pipe, flange and valve standards and correct sizes, and prepare bolts.
  2. Check that the valves, flanges and pipe connections are not deformed or misaligned.
  3. Clean valves, pipes and flange connection surfaces. Make sure there is no rust, corrosion and debris to create a good sealing surface.
  4. Install carefully and make sure not to damage the valve seat and flange sealing surface. Adjust the end faces of the flanges on the pipes to ensure there is enough space between them to facilitate later maintenance and replacement of the valve.
  5. After the valve is centered in place, insert the bolts, being careful not to tighten them completely. First operate the valve and make sure it operates freely. Once confirmed, tighten the bolts in stages, working in a diagonal pattern as you would a car tire to apply pressure evenly on the flange.


     I am the author of this article and the CEO and Marketing Director of SWDPLASTIC with 15 years of experience in the valve and pipeline industry. If you have any questions, you can contact me anytime.


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