Butterfly valves are quarter-turn rotational motion valves use in pipelines to shut off flow. Butterfly valves are often describe as being able to regulate flow. We do not recommend doing this, however, as it can damage the valve disk and negatively impact the seal. They are use by a wide range of industries and process media, particularly in water supply, collection, and distribution, as well as pumping stations. They have a wide range of applications, especially in flow isolation. Their key advantages over other valve families include their simple construction and compactness, which result in lighter weights and lower costs, as well as smaller installation footprints and faster actuation speeds.
Butterfly valves are double eccentric (double offset) flange types. Double offsets or eccentricities refer to the fact that this valve design involves two offsets of the disc concerning the valve body center or axis of rotation.
Butterfly Valve Parts
The major components of a butterfly valve are as follows:
- Valve Body
The main types of pipe flanges are flanged, double lug, and wafer. The valve body fits between the flanges.
- Disc
A disc attached to the valve body functions as a gate that stops or throttles fluid flow, much like a gate on a gate valve or a ball on a ball valve. The disc is usually boring to receive the stem. Different disc designs, orientations, and materials improve flow, sealing, or operating torque.
- Seat
Discs are secure in place in the close position in the internal valve body by an elastomer or metal anti-leak seal that ensures complete shutoff. With stainless steel weld-filled and micro-finished integral body seats, the 9881k series offers corrosion and erosion resistance. With this special type of seat design, it is possible to manufacture the valve drop-tight in compliance with EN12266-A.
- Stem
Often called the stem, the valve shaft connects the disc to the actuation mechanism and transmits torque.
- Seals
Multiple seals are present at various interfaces within the valve to ensure a tight seal during operation, as well as to isolate the process media from the valve’s internal components for a more flexible and cost-effective design.
Discs are seal on the seat face by a continuous T-profile resilient sealing ring that is held on the periphery of the disc by a retaining ring, preventing the sealing ring from rolling out. The sealing ring is press against the seat face in the close position, providing a tight seal between the upstream and downstream ends. Because of the double eccentric disc design, the sealing ring is completely unstressing in the open position.
By eliminating interaction between the process media and the stem/shaft, our multiple O-ring shaft sealing system ensures a maintenance-free seal for the entire life of the valve. Besides, there are smaller more common components such as bushings, bearings, and fasteners that are a part of most other valve constructions as well. In the actuation section. We will describe some of the components on the actuation end, such as the handle, lever, gearbox, and handwheel.
Butterfly Valve: Working Principle
A butterfly valve is relatively simple to construct, with the valve disc rotating to control fluid flow. When the disc is close, it blocks the valve bore, while in the open position. It is oriente perpendicular to the flow direction to allow it to flow. Butterfly valves provide bidirectional flow and shutoff capabilities. However, they are not full-bore, so they are not suitable for pigging or swabbing. The body material is ductile iron with epoxy powder coating on both the interior and exterior surfaces. Handwheels, gears, actuators, or some combination are usually use to operate the valves. Depending on the application requirements and technical specifications. The actuation methods will discuss later in the article.
Butterfly Valve Actuation
A butterfly valve can operate in multiple ways – manually, semi-manually, or automatically.
- Electric: Typically use for time-sensitive applications or high precision regulation, these valves are controlled by an electric actuator using a 4-20mA signal.
- Pneumatic: It is also use in high precision applications and is actuated by compressed air.
- Hydraulic: Typically use for applications that require large torques for opening and closing the valve, such as high pressure or high viscosity.
- Manual: Handwheels, cranks, or lever is use to operate manually operated butter valves. Smaller manual valves are usually operate by levers. With larger sizes, handwheels are provided and a gearbox is provided to transmit torque with a high mechanical advantage. In circumstances where the valve is buri underground without a manhole. Manual actuation can done by an extension spindle, adapter/square cap, and a corresponding T-key from the ground level.
Because butterfly valves require less torque, sizing and installing actuators are less expensive than other valves, like gate valves.
The 9881k series comes standard with a handwheel actuation and worm wheel gearbox with a feature that minimizes gear backlash and ensures correct operation and tightness of the end device. Furthermore, it is compatible with external actuators with an ISO 5210 top flange for mounting multi-turn actuators.
Advantages of Butterfly Valves
Butterfly valves can offer significant advantages over other types of valves. Especially for dimensions greater than DN 200 (200 mm) in size:
- Lightweight and Compact: Butterfly valves have a compact design and a smaller face-to-face dimension, which results in a smaller installation footprint and lower installation costs, including labor, equipment, and piping support.
- Low Maintenance Requirements: An inherently simple, economic design with few moving parts and fewer wear points reduces the need for maintenance.
- Fast Acting: A 90° rotation of the handle, or the actuation mechanism, closes or opens the valve completely. The gearbox is often use in the actuation mechanism of larger butterfly valves. Reduces the operational torque and simplifies the operation of the valve, but at the expense of speed.
- Low Cost: Due to their simple design, butterfly valves require less material, are easier to design and manufacture, and are often more economical than other valve types. The savings are mainly realize in larger valve sizes, typically over DN 300.
- Versatility: A butterfly valve has many applications, including the ability to be installed underground.
Aira Euro Automation is a leading butterfly valve manufacturer in Kuwait. Aira has a wide range of butterfly valves which are operated by a pneumatic actuator, gear & lever.
Also, read Advantages of Using Parker Tube Fittings