what is a butterfly valve used for?
Table of Contents
01 What is a butterfly valve?
Butterfly valves are rotary valves used to stop flow in pipelines. They are common in water systems for their simple, compact design and fast operation.
While butterfly valves can throttle flow, this is not recommended. It can damage the disk and sealing. Butterfly valves are best for on/off duty.
Butterfly valves have a disc that turns 90 degrees to open and close the flowpath. The shaft is offset from the disc center, known as the double eccentric or double offset design.
JHY butterfly valves use the double offset construction. The dual offset of the disc from the rotation axis improves sealing when closed while allowing full flow when open.
02 Butterfly valve components
Butterfly valves have become a staple in various industries due to their simple yet effective design and versatile applications. At the heart of these valves lies a collection of crucial components that work in harmony to regulate fluid flow. Let’s delve into the essential components of butterfly valves and explore their respective functions.
1. Valve Body:
The valve body serves as the structural foundation of the butterfly valve, providing the connection point between the valve and the piping system. It houses the internal components and ensures a secure seal against external pressure. Common valve body designs include flanged, double lug, and wafer types, each catering to specific piping configurations.
2. Disc:
The disc, often referred to as the butterfly, is the heart of the valve’s flow control mechanism. It resembles a rotating gate that pivots within the valve body to open or obstruct the flow path. The disc’s material, orientation, and design significantly impact flow characteristics, sealing effectiveness, and operating torque. For instance, the eccentric disc design reduces seal wear and operating torque.
3. Seat:
A critical component for achieving complete shutoff, the seat is a resilient elastomer or metal seal that lines the internal valve body. It provides a tight seal against the disc in the closed position, preventing fluid leakage. The seat’s material and design play a vital role in resisting corrosion, erosion, and wear.
4. Stem:
The stem, also known as the shaft, acts as the mechanical link between the disc and the actuation mechanism. It transmits the torque required to rotate the disc, thereby regulating fluid flow. The stem’s material and design must withstand the forces exerted during operation and maintain its integrity under various operating conditions.
5. Seals:
Seals are strategically positioned at various interfaces within the valve to prevent leakage and protect internal components from exposure to the process media. They contribute to the valve’s overall reliability and maintainability. For instance, the T-profile resilient sealing ring on the disc ensures a tight seal against the seat, while the multiple O-ring shaft sealing system protects the stem from corrosion and wear.
6. Additional Components:
While not as prominent as the primary components, several smaller parts play crucial roles in the butterfly valve’s functionality. Bushings, bearings, and fasteners provide structural support, minimize friction, and ensure secure assembly. These components contribute to the valve’s overall performance and longevity.
Butterfly valves rely on a harmonious interplay of various components to effectively regulate fluid flow. Understanding the function and design of these components is essential for selecting and maintaining butterfly valves in various industrial applications.
Butterfly Valve Top Flange
A butterfly valve top flange is a circular metal plate attached to the top of a butterfly valve. It's used to connect the valve to other pipes or equipment using bolts or studs.
Butterfly Valve V-sealing
V-sealing in butterfly valves refers to a specific design of the valve disc and seat that provides a tight and reliable seal.
Butterfly Valve Bearing
Butterfly valves rely on bearings to support the shaft that the disc is mounted on, enabling smooth operation and reducing friction.
Valve Stem
A butterfly valve stem is a crucial component that connects the valve handle or actuator to the disc, allowing you to control the flow of fluid through the valve.
Valve Disc
The butterfly valve disc is the central moving component responsible for regulating flow within the valve.
Valve Body
The butterfly valve body is the heart of the valve, housing all the internal components and providing the structure for fluid flow control.
Valve Seat
A butterfly valve seat is a device used in a butterfly valve to provide a tight seal when the valve is closed. It is typically made of a soft material, such as rubber or elastomer, and is located in the valve body.
Locator Holes
Locator holes are used for convenient and accurate installation.
03 Butterfly valve actuation
Butterfly valves offer various actuation mechanisms to suit a wide range of applications, from manual operation to fully automated control. Each actuation method presents unique advantages and considerations.
Electric Actuation:
Electrically actuated butterfly valves employ electric actuators, powered by a 4-20mA control signal, to precisely regulate fluid flow. This method is particularly well-suited for applications requiring high precision and time-sensitive control.
Pneumatic Actuation:
Pneumatic actuation utilizes compressed air to operate the butterfly valve, providing accurate control and rapid response times. This method is also suitable for high-precision applications and offers the advantage of readily available compressed air in many industrial settings.
Manual Actuation:
Manually operated butterfly valves rely on a handwheel, crank, or lever to rotate the valve disc. Smaller valves typically use a lever, while larger valves employ handwheels combined with gearboxes to amplify torque. For buried valves without manholes, extension spindles, adapters, and T-keys allow for operation from the ground level.
Selection Considerations:
The choice of actuation mechanism depends on various factors, including:
Application Requirements: Precision, torque requirements, and response times.
Power Availability: Availability of electrical power, compressed air, or hydraulics.
Environmental Conditions: Exposure to harsh environments or hazardous materials.
Accessibility: Remote or buried valves may require extended spindles or actuators.
Butterfly valves, coupled with appropriate actuation mechanisms, provide versatile solutions for a wide spectrum of fluid control applications. The selection of the optimal actuation method ensures efficient, reliable, and precise control of fluid flow in diverse industrial settings.
04 how does a butterfly valve work?
Butterfly valves have gained widespread popularity due to their straightforward design and adaptability to a wide range of applications. The fundamental principle behind their operation lies in the rotation of a valve disc, which effectively controls the passage of fluid. In the closed position, the disc completely obstructs the valve bore, halting fluid flow. Conversely, in the open position, the disc aligns perpendicular to the flow direction, allowing unobstructed passage. Butterfly valves typically offer bi-directional flow and shutoff capability, making them versatile solutions for various fluid control tasks.
While butterfly valves excel in many applications, they are not suitable for pigging or swabbing due to their non-full-bore design. Pigging and swabbing techniques involve inserting cleaning devices into pipelines to remove debris or perform maintenance tasks. The restricted internal space of butterfly valves renders these techniques impractical.
The body material of butterfly valves is typically ductile iron, which provides strength and durability. An epoxy powder coat is applied to both the internal and external surfaces of the valve, offering enhanced resistance to corrosion and wear.
Butterfly valves are commonly operated using handwheels, gears, or actuators, either individually or in combination. The choice of actuation mechanism depends on the specific requirements of the application, considering factors such as flow rate, pressure, and accessibility.
Butterfly valves stand out for their simple yet effective design, making them a preferred choice for a variety of fluid control applications. Their bi-directional flow capability and shutoff capacity further enhance their versatility. While their non-full-bore design precludes pigging and swabbing techniques, their epoxy-coated ductile iron construction ensures long-lasting performance. The selection of actuation mechanisms, ranging from handwheels to actuators, caters to the diverse needs of various applications.
05 Types of butterfly valves
- Wafer type – This is the most basic type of butterfly valve. It consists of a valve body and a disc attached to a shaft. The valve is designed to be sandwiched between two pipe flanges or fittings. Wafer butterfly valves are lightweight, simple, and inexpensive.
- Lug type – This type has extended flanges (lugs) on both sides of the valve body. The lugs have holes for bolting the valve to flanged pipe fittings. Lug butterfly valves provide a sturdier connection than wafer types. They are also easier to install and replace.
- Double flanged type – As the name suggests, this butterfly valve has two integral flanges, one on each side of the valve body. The flanges allow the valve to be bolted directly to flanged fittings without having to be sandwiched between them. Double flanged butterfly valves provide a more compact installation but are heavier and more expensive.
- Double-eccentric type – The double-eccentric type of butterfly valve refers to a design where the disc is offset from the centerline of the valve body and shaft. This offset allows the disc to completely disengage from the seat when the valve is fully open. This design feature helps reduce wear and improves sealing performance.
06 What is the main advantage of a butterfly valve?
- Compact Design: Butterfly valves have a compact and lightweight design compared to other types of valves, such as ball valves or gate valves. This compact design makes them easy to install and maintain, even in tight spaces.
- Low Pressure Drop: Butterfly valves offer low pressure drop, which means they have minimal resistance to fluid flow. This low pressure drop results in energy savings and reduced pumping costs.
- Bi-directional Flow: Butterfly valves can handle fluid flow in both directions, making them versatile for various applications. This bi-directional flow capability eliminates the need for check valves, simplifying piping systems.
- Tight Shutoff: Butterfly valves provide tight shutoff, ensuring complete isolation of fluid flow when closed. This tight shutoff capability is critical for applications where preventing leaks is essential.
- Quick Operation: Butterfly valves can be opened and closed quickly, making them suitable for applications requiring rapid flow control.
- Easy Maintenance: Butterfly valves are relatively easy to maintain, requiring minimal downtime and maintenance costs. The simple design and fewer moving parts contribute to their ease of maintenance.
- Wide Range of Materials: Butterfly valves are available in a wide range of materials, including stainless steel, ductile iron, and PVC, making them suitable for various applications and fluids.
- Cost-effective: Butterfly valves are generally more cost-effective than other types of valves, making them an attractive option for many applications.
- Variety of Actuation Options: Butterfly valves can be actuated using various methods, including manual, electric, pneumatic, and hydraulic actuation, providing flexibility for different applications and control requirements.
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