Butterfly valves: what are they?

Butterfly valves are quarter-turn rotational motion valves use in pipelines to shut off flow. There is a common belief that butterfly valves can use to control the flow. We do not recommend doing this, as it can damage the valve disk and have a negative impact on the sealing. The devices use in a wide range of process media and industries, including water supply, collection, and distribution, and pumping stations, where they have a wide range of applications, including flow isolation. Their key advantages over other valve families are their simple construction and compactness, resulting in lighter weight and lower cost end products, with smaller installation footprints and faster actuation speeds.

Butterfly valves made by Aira Euro Automation are double eccentric type (double offset). Double offset or eccentricity refers to the fact that this valve design involves two offsets of the disc from the valve body’s center or the stem’s axis of rotation.

Parts for butterfly valves

A butterfly valve consists of the following components:

• Valve Body

  The valve body fits between the pipe flanges – the most common end connections are flanged, double lug, and wafer.

• Disc

There is a disc attach to the valve body that functions as a gate that stops or throttles fluid flow; it can be compar to the gate in a gate valve or the ball in a ball valve. A disc typically bore to receive the stem or shaft. There are many variations in disc design, orientation, and material to improve flow, sealing, and/or torque.

• Seat

An elastomer or metal anti-leak seal surrounds the internal valve body and secures the disc in place when it is close to ensure complete shutoff. The stainless steel weld-filled and micro-finished integral body seats of the 9881k series provide corrosion and erosion resistance. By using this special type of seat design, it is possible to manufacture the valve drop tight in accordance with EN12266-A.

• Stem

The valve shaft, also known as the stem, is the component that connects the disc to the actuation mechanism and transmits torque through this component.

• Seals

Seals are present at multiple interfaces within the valve in order either to ensure a tight seal during operation or to isolate the process media from the valve’s internal components for a more flexible and cost-efficient design.

A continuous T-profile resilient sealing ring is use to seal the seat face. The sealing ring hold on the disc by a retaining ring, thus preventing it from rolling out. In the close position, the sealing ring is press against the seat face. Providing a tight seal both upstream and downstream. Because of the double eccentric disc design, the sealing ring is completely unstressed in the open position.

The multiple O-ring shaft sealing system eliminates interaction between the process media and the stem/shaft. Ensuring a maintenance-free seal for the duration of the valve’s life. Moreover, there are smaller more common components like bushings, bearings, and fasteners that use in most other valve constructions. We will cover some of the components found on the actuation end, such as the handle, lever, gearbox, and handwheel, in the actuation section.

Butterfly Valves: Working Principle

Butterfly valves are relatively simple to build, with the rotation of the disc controlling the flow of fluid. When the disc closes. It blocks the valve bore, while when it is open. It is oriente perpendicular to the flow direction. butterfly valve manufacturer can provide bi-directional flow and shutoff. Although they are not full-bore, they are unsuitable for pigging or swabbing. The body is made from ductile iron with an epoxy powder coat on both internal and external surfaces. In most cases, valves operate by handwheels, gears, actuators, or a combination of these. Depending on the specific application requirements and technical specifications. We will discuss actuation methods later in the article.

Butterfly valves Actuation

Butterfly valves can be operate in several ways – manually, semi-manually, or automatically.

• Electric: Typically used for high precision regulation and time-sensitive applications, these valves are controlled by an electric actuator with 4-20 mA control.
• Pneumatic: Used for high-precision applications and uses compressed air for actuation.
• Hydraulic: These valves are typically used for applications requiring high torques for opening and closing, such as high pressure and high viscosity.
• Manual: In manually operated butter valves, a handwheel, crank, or lever is used to operate the valve. Smaller manual valves are typically equip with levers. Larger sizes feature handwheels accompanied by a gearbox that transfers torque with a high mechanical advantage. When the valve sets underground without a manhole. Manual actuation doing from the ground level with an extension spindle, adapter, and corresponding T-key.

Butterfly valves require less torque than other valves, including gate valves, so they are less expensive to install and size.

Read, more The most underrated Pneumatic Globe Control Valve

Standard on the 9881k series is a handwheel actuation and wormwheel gearbox with a self-locking design that minimizes gear backlash and ensures proper operation and tightness of the device. Furthermore, it is compatible with external actuators with an ISO 5210 top flange for mounting multi-turn actuators.

Advantages of Butterfly Valves

Depending on the application, butterfly valves can offer significant advantages over other types of valves. Especially for diameters over DN 200 (200 mm):

1. Lightweight and Compact: Because butterfly valves are compact and have a smaller face-to-face dimension. They have a smaller installation footprint and lower installation costs, including labour, equipment, and piping support.
2. Low Maintenance Requirements: The simple, economical design consists of fewer moving parts and thus fewer wear points, thereby reducing their maintenance requirements.
3. Fast Acting: The handle, or the actuation mechanism, can be rotated 90° to close or open the valve entirely. Larger butterfly valves, on the other hand, often require a gearbox to act as part of the actuation mechanism. Which reduces the operating torque and simplifies valve operation, but at the expense of speed.
4. Low Cost: Butterfly valves are simpler to design and manufacture because of their simple design, and are often more economical than other valve types. Savings are mainly realize in larger valve sizes, typically over DN 300.
5. Versatility: The butterfly valve has a wide variety of uses, including the ability to be installed underground.