Butterfly Valves: Types, Functions, Materials and Benefits

16 Jun.,2025

 

Butterfly Valves: Types, Functions, Materials and Benefits

Butterfly Valves: Types, Functions, Materials and Benefits

Chapter 1: What Exactly Is a Butterfly Valve?

A butterfly valve is a type of quarter-turn rotary control mechanism used to regulate the flow of fluids in a pipeline system. Its operation is based on a rotating disc situated directly within the flow route. This disc is maneuvered by an external actuator, which is linked via a stem. When the disc aligns itself parallel with the flow, it fully obstructs fluid passage. Conversely, when it is set perpendicularly, the fluid can freely flow through. A 90-degree rotation of the disc is needed to open or seal the valve.

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Similar to ball valves and plug valves, butterfly valves are quarter-turn valves. These devices exhibit a straightforward construction and operational principle and are designed compactly to fit between two pipe flanges. They can be manually operated or automated using an actuation system incorporated into the pipeline's process control. While ideal for simple on-off applications, their functionality for controlling flow throttling is somewhat restricted.

Available in a wide array of models and configurations, butterfly valves are built to sustain different temperature ranges, pressures, and flow volumes. Each valve type is precisely engineered to meet the unique needs of pipeline systems managing both liquid and gaseous flows.

Chapter 2: What are the Components of a Butterfly Valve?

The primary components of a butterfly valve include the following:


  • Valve Body: Made from a tough and rigid material, the valve body houses and protects the disc and other internal components of the butterfly valve. It links the valve to the piping system and to the external operating mechanism that controls the disc. Butterfly valve bodies are engineered for strength and resilience, ensuring the integrity of the entire industrial valve assembly within demanding environments such as chemical processing, water treatment plants, oil and gas facilities, and HVAC systems.
  • Disc: The disc permits, regulates, and stops the flow of fluid (including liquids, gases, and slurries) in the pipeline. Flow is controlled by the rotary motion of the disc, which acts as the closing mechanism within the valve. The discharge flow rate depends on the degree of disc opening, making the disc a crucial throttling element for flow control applications.

    When the disc is perpendicular to the flow’s cross-sectional area, fluid is fully obstructed from passing through the valve. Conversely, rotating the disc allows fluid to flow through the space between the seat and the disc. A 90° rotation from the closed position enables full opening or closing of the valve, while positioning the disc at intermediate angles provides effective throttling and regulation of flow. Because of its efficient design, the butterfly valve disc is often compared to the ball in ball valves or a plug in plug valves, and is commonly used in isolation and control processes across industries.

  • Stem: The stem is a shaft that connects the disc to the external operating mechanism (such as a lever, gearbox, or actuator). It is sealed with O-rings and bushings to prevent fluid leakage and ensure the reliability of the valve. The stem may be constructed as a one-piece shaft or a two-piece (split-stem) shaft. Stem placement and its connection to the disc vary depending on the butterfly valve type, such as concentric, double-offset (high-performance), or triple-offset (torque-seated) valves. The stem’s durability is essential for maintaining operational life, especially in high-cycle industrial valve applications.
  • Seat or Sealing Ring: The valve seat for standard concentric butterfly valves is a ring providing a seal between the disc edge and the valve body in a closed position. This sealing action prevents leakage of fluid past the butterfly valve, which is critical in applications where tight shutoff is required (such as in potable water systems and sanitary applications). The seat must be composed of a material with a low coefficient of friction due to the sliding motion of the disc during operation.

    Butterfly valve seats can be categorized as soft seats or metal seats. Soft seats—made from elastomeric or thermoplastic materials like EPDM, PTFE, or NBR—are often used for lower temperature and pressure applications, providing bubble-tight shutoff. Metal seats, typically constructed from stainless steel or other alloys, are designed for high-temperature, high-pressure, or abrasive service, offering extended service life though sometimes at the expense of minimal leakage. The selection of seat material directly impacts the temperature, pressure, and chemical compatibility of the butterfly valve.

  • Operating Mechanism: The external operating mechanism of a butterfly valve controls fluid flow through the valve, enabling precise on-off or throttling control. Valves can be operated by manual rotation (via lever or handwheel) or by automatic actuation for process automation and remote valve control.

    Manual operation involves applying torque to the lever or handwheel connected to the stem, setting the valve in fully-closed, fully-open, or partially-open positions for regulating media. Larger butterfly valves or those requiring frequent operation are equipped with gear operators or chain wheel mechanisms to increase torque and facilitate easier valve operation. For high-cycle or remotely located installations, butterfly valves employ actuators—these may be electric (electromechanical), pneumatic (using compressed air to move a piston or diaphragm), or hydraulic (operated by fluid pressure). Advanced actuation also supports networked process control in industrial automation and building management systems, increasing efficiency and reducing requirements for manual intervention.

  • Triple Offset: The triple offset design incorporates three distinct offsets within the valve, each strategically placed to create an offset conical sealing profile and a right-angle cone. This engineering enables bubble-tight shutoff and significantly reduces wear during operation, making triple offset butterfly valves ideal for critical service applications—including steam, high-pressure gas, or corrosive chemical services—where zero leakage and longevity are crucial. The triple offset butterfly valve design is a preferred choice for high-performance, bidirectional isolation in complex process systems.
  • Bushing or Bearing: The quality and type of bushing or bearing directly impact the service life and operational reliability of a butterfly valve. Industrial-grade bushings are engineered to resist corrosion, chemical attack, and wear, and are used for smooth shaft rotation, precision control, and minimizing friction during actuation cycles. In demanding environments such as petrochemical processing, water and wastewater treatment, chlorine service, pulp and paper production, and electroplating, advanced bearings are often self-lubricating for improved durability and reduced maintenance requirements. The selection of material—for example, PTFE, bronze, or composite polymer—further enhances the valve's performance and dependability.

Additional Key Features

  • End Connection Types: Butterfly valves are available with various end connections—including wafer, lug, flanged, and butt-weld—which determine how the valve is installed in the pipeline and affect compatibility with adjoining equipment. End connection selection is essential for meeting industry standards and ensuring leak-free installation.
  • Pressure and Temperature Ratings: Each butterfly valve is rated for specific pressure (ANSI, PN, or JIS class) and temperature ranges. Choosing an appropriate rating ensures safe and reliable valve operation under process conditions. For high-performance or critical process service, always verify valve ratings with manufacturer specifications.
  • Industry Standards and Certifications: Leading butterfly valve manufacturers comply with international standards such as API 609, ISO , MSS SP-67, and NSF/ANSI 61, ensuring quality, safety, and suitability for use in potable water, food processing, and other regulated industries.

When selecting, specifying, or replacing a butterfly valve, consider not just its internal components, but also materials of construction, performance requirements, end connection types, and compliance with relevant standards. These factors will help ensure optimal performance, longevity, and suitability for your industrial or commercial fluid handling application.

Leading Manufacturers and Suppliers

Chapter 3: What are the different types of butterfly valves?

Butterfly valves are versatile flow control devices engineered to provide effective and dependable shut-off and throttling in industrial piping systems. These quarter-turn valves are chosen for their compact design, low pressure drop, and rapid operation. Butterfly valves come in two primary designs: centric (concentric) and eccentric. Centric butterfly valves have the stem positioned centrally through the valve disc, while eccentric butterfly valves feature one or more stem offsets, separated from the disc’s centerline for specialized performance. Eccentric valves are further divided by the number of offsets—single, double, or triple offset configurations—offering enhanced sealing, reduced friction, and higher durability, making butterfly valves highly desirable in process control, water treatment, oil & gas, chemical, HVAC, and power generation sectors.

Zero Offset Butterfly Valves (Resilient Seat Butterfly Valves)

Zero offset butterfly valves, also known as concentric butterfly valves, feature a stem that runs through the centerline of the disc, precisely centered within the resilient seat and the valve body. When closed, all elements align concentrically. The disc can rotate a full 360°, and in its open position, fluid flow is divided efficiently on either side. A key advantage is that the flowing media does not contact the metal valve body, as the seat material, typically rubber or elastomer, provides a protective barrier.

These valves utilize resilient soft seats, relying on seat deformation for tight shut-off and leak-free sealing. However, the sliding action of the disc against the seat creates friction, potentially reducing cycle life under frequent use. Common materials for the seat include EPDM, NBR, and PTFE, making zero offset butterfly valves well-suited for low to medium pressure applications (up to 250 psi) and moderate temperature ranges (up to 400°F). This makes them ideal for potable water, air, non-corrosive gases, and basic chemical services as cost-effective isolation or regulation valves.


Double Offset Butterfly Valve (High-Performance Butterfly Valves)

Double offset butterfly valves, often referred to as high-performance butterfly valves, are engineered with two distinct stem offsets relative to the seat centerline and body centerline. The first offset positions the stem behind the seat axis, while the second moves the stem off from the pipe’s vertical axis. This configuration “lifts” the seat from the disc during the opening and closing movements, drastically reducing friction and wear—especially around the first and last 10 degrees of movement.

Double offset butterfly valves typically feature a soft seat with a metal backing for enhanced performance at higher pressures and temperatures than zero offset models. Their robust construction makes them suitable for demanding liquid and gas applications, including water treatment plants, chemical process lines, HVAC systems, fire protection, and industrial utilities. They are recognized for delivering improved tightness, extended cycle life, and reliable performance in systems where standard resilient-seated valves may not suffice.


Triple Offset Butterfly Valve

Triple offset butterfly valves add a third, angular offset to the body’s sealing cone axis in addition to the initial two offsets, producing a right-angled, conical seating geometry. With this design, the seat and disc only contact each other momentarily at the closed position, virtually eliminating friction during operation. This allows for precise shut-off and exceptional durability under severe operating conditions.

Constructed with robust metal seats—often in stainless steel or alloy—the triple offset butterfly valve excels in applications demanding tight shut-off at high pressures and high temperatures. This configuration is ideal for managing superheated steam, high-temperature liquids, aggressive chemicals, and challenging gases found in power generation, oil and gas processing, petrochemical operations, pulp and paper manufacturing, and offshore pipelines. Metal-seated triple offset valves are also fire-safe and suitable for critical process control where zero leakage is essential.


In addition to superior sealing and high cycle life, triple offset butterfly valves demonstrate outstanding resistance to thermal and mechanical shock, extreme pressure fluctuations, and corrosive environments. Their unique construction makes them the preferred choice in safety-critical and severe service applications requiring reliable isolation.

Butterfly valves can also be categorized according to their connection type and installation method within a piping system:

Wafer Butterfly Valve

Wafer butterfly valves are slim-profile valves that are installed between two pipe flanges. Long through-bolts traverse the valve body, which may have, or lack, external flange holes. To prevent backflow and leakage, O-rings or flat face gaskets are compressed on both sides of the valve body, creating a tight seal. Wafer-style butterfly valves are a popular, cost-effective choice for systems requiring light weight, easy installation, and a lower investment cost.

While wafer butterfly valves provide excellent, compact shut-off for liquids and gases, they are not recommended for dead-end (end-of-line) service as they cannot withstand unbalanced pressure when one side is removed. Pipeline maintenance or component replacement normally necessitates full shutdown of the system. This style is generally suitable for moderate pressure and temperature systems and is not ideal for high-temperature, steam, or harsh chemical services that may cause thermal expansion or seat degradation.


Lug Butterfly Valve

Lug butterfly valves install between two pipe flanges using threaded mounting lugs protruding from the valve body. Specialized bolts connect each side directly, and unlike wafer butterfly valves, lug valves permit disconnection of one pipeline segment without disturbing the other side. This “dead-end service” capability makes them versatile for on-line maintenance and point-of-isolation requirements.

Lug-style valves must withstand added load, as the valve body supports the pipeline segment when used in end-of-line service. This increases engineering considerations for seat integrity and permissible pressure ratings. They are frequently used in water distribution, process isolation, and industrial plant piping where system flexibility and streamlined repairs are required.


Double-Flanged Butterfly Valve

Double-flanged butterfly valves feature flange connections on both sides of the valve body, precisely matching pipe flanges with dedicated bolts and nuts for secure, vibration-resistant installation. This robust mounting arrangement provides optimal strength, alignment, and leak prevention—especially for large-diameter pipelines and critical systems subject to frequent operation, surges, or high pressures. Municipal water, wastewater treatment, and major process lines often utilize double-flanged valves due to their stability and operator safety.


Butt-Weld Butterfly Valves

Butt-weld butterfly valves are welded directly into the pipeline, creating a permanent, pressure-tight joint ideal for severe service, high-pressure, or high-temperature environments. Their seamless integration minimizes potential leak paths and withstands pipe stresses, making them the preferred solution in power plants, oil and gas transmission networks, chemical manufacturing, and applications with strict leakage or fire safety codes. Butt-welded butterfly valves offer enhanced mechanical strength and reduced maintenance.


Top Entry Butterfly Valves

Top entry butterfly valves are engineered for simplified maintenance and minimal downtime. Their unique construction enables the removal of the bonnet, providing direct access to the stem, disc, and seat from above. This design eliminates the need for full pipeline disassembly when replacing internal parts, allowing cost-effective valve repair, part replacement, or inspection in-line. Top entry designs are especially advantageous in critical process or hazardous service environments where continuous uptime is paramount.


Butterfly valves are also classified as “non-wetted” or “wetted” valves according to their construction and degree of exposure of internal surfaces to the operating media:

  • Non-Wetted Valves: Non-wetted butterfly valves feature a valve body and stem isolated from the process fluid by a durable lining or coating, typically made from corrosion-resistant plastics (such as PTFE or Teflon®) or resilient elastomers. This design enables use of cost-effective valve materials even in corrosive or abrasive applications, as the lining protects critical metal components from chemical attack, scaling, or erosion.
  • Wetted Valves: Wetted butterfly valves have the valve body and stem in direct contact with the flowing media. The selection of metallic or alloy bodies must align with the chemical properties, temperature, and pressure conditions of the application to ensure corrosion resistance and valve longevity.

In summary, understanding the types of butterfly valves—including seat design (resilient seat, high-performance or triple offset), installation method (wafer, lug, flanged, butt-weld, top entry), and material options (wetted or non-wetted)—is fundamental for selecting the right valve for your flow control needs. When evaluating butterfly valve products, consider the process fluid’s pressure, temperature, media composition, desired shut-off tightness, ease of maintenance, and compliance with relevant industry standards (such as API, ASME, or ISO). Advanced butterfly valve automation options, including pneumatic or electric actuators, can further optimize system performance and reliability for complex piping infrastructures.

Chapter 4: What materials are commonly used in the construction of butterfly valves?

The valve body needs to have high toughness and rigidity to safeguard the internal components of the butterfly valve. Similarly, the stem and disc must exhibit these qualities to endure fluid pressures. Butterfly valve components can be constructed from the following materials:

Metal Butterfly Valves

Stainless Steel

Stainless steel is an alloy with a high chromium content (10.5-30%) and small amounts of nickel and molybdenum. It is renowned for its exceptional strength, toughness, and resistance to corrosion and weathering. The corrosion resistance is primarily due to the chromium, which forms a thin, protective chromium oxide layer that prevents oxygen from penetrating the material. If the surface is damaged, this layer can regenerate with the help of oxygen, thus preventing rust. Molybdenum contributes to resistance against pitting corrosion.

Stainless steel butterfly valves are excellent for handling acidic and corrosive fluids, a wide range of pressures, and a wide range of temperatures. Austenitic stainless steel is ideal for cryogenic processes, while duplex stainless steel is used for higher pressure. 316 Stainless Steel is the preferred stainless-steel grade.


Carbon Steel

Carbon steel is an alloy with a carbon content of up to 2.5%. It offers good mechanical properties and is suitable for applications that do not have specialized requirements. Common grades of carbon steel used for butterfly valves include ASTM A216 WCB (Welded Cast B-grade) and LCC (Low Carbon Content). The WCB grade is suited for high-temperature applications, while the LCC grade is appropriate for low-temperature environments. These valves are typically produced using a sand-casting process for both the body and the disc.

While carbon steel butterfly valves are more cost-effective compared to their stainless steel counterparts, they are not suitable for handling corrosive fluids.


Hastelloy

Hastelloy is an alloy made of nickel, chromium, and molybdenum, and was the first alloy developed by Haynes International, Inc. It is known for its high strength at elevated temperatures and its excellent resistance to corrosion, cracking, and both oxidizing and reducing agents. Hastelloy is suitable for handling acids such as nitric, hydrochloric, and sulfuric at moderate temperatures.

Hastelloy butterfly valves are commonly used in applications involving high temperatures, high pressures, and corrosive environments, including those found in oil and gas processing and power generation.


Brass

Brass is an alloy composed of copper and zinc, known for its toughness, durability, and ability to withstand high temperatures. It is prized for its resistance to corrosion and biofouling, as well as its antimicrobial properties, which help prevent the growth of microbes and biofilms on its surface.

Brass butterfly valves are commonly used in applications such as water purification, wastewater treatment, and in the food and pharmaceutical industries. However, they are not suitable for handling water with high chlorine content, such as seawater or swimming pool water, due to the risk of dezincification caused by chlorine.


Nickel Alloys

Nickel alloys are renowned for their excellent resistance to corrosion, harsh environments, and high temperatures. They typically outperform stainless steel in extremely corrosive conditions. However, nickel butterfly valves tend to have a higher density and come at a greater cost.


Titanium Alloys

Titanium alloys offer a high strength-to-weight ratio and are well-regarded for their resistance to corrosion and biofouling. They are suitable for use in seawater environments and water treatment applications due to their non-toxic nature. Despite these advantages, titanium butterfly valves are also quite expensive.

Nickel Aluminum Bronze

Nickel Aluminum Bronze is a copper-based alloy that includes 10% aluminum, 5% nickel, and 5% iron. This alloy is notable for its resistance to corrosion, antimicrobial properties, and ability to prevent biofouling. Nickel Aluminum Bronze butterfly valves are commonly used in seawater environments, such as offshore piping, as well as in water purification and wastewater treatment applications.

Plastic Butterfly Valves

Butterfly valves can also be constructed from rigid plastic materials. Typically, plastic butterfly valves are lighter and more cost-effective than their metal counterparts. However, plastic materials have lower melting points, which restricts their maximum operating temperature.

Polyvinyl Chloride Butterfly Valves (PVC)

PVC is a strong and rigid material commonly used in pipes, fittings, and valves. PVC butterfly valves are known for their durability and resistance to corrosion. They are suitable for handling most chemicals, although they should not be used with hydrocarbons or aromatic compounds. PVC valves are hygienic, easy to clean, and simple to assemble, making them ideal for applications in food and beverage processing. They are also used in water supply distribution, irrigation, plumbing, and water and wastewater treatment. PVC butterfly valves have a maximum operating temperature of 60°C and a pressure rating of 150 psi.

Chlorinated Polyvinyl Chloride Butterfly Valves (CPVC)

CPVC contains more chlorine than PVC and is produced through the free radical chlorination of PVC. This modification allows CPVC to handle higher temperatures, up to 93.3°C, and enhances its flexibility. However, CPVC is generally more expensive than PVC. CPVC butterfly valves are commonly used in both cold and hot potable water systems, industrial liquid handling, swimming pools, fountains, and other applications.

Polypropylene Butterfly Valves (PP)

PP (Polypropylene) butterfly valves are known for their exceptional strength and durability in harsh environments. They resist corrosion, biofouling, and UV degradation, making them suitable for handling a wide range of chemicals and corrosive agents. However, they have selective compatibility with certain organic substances and solvents. PP butterfly valves are commonly used in aquaculture, water and wastewater treatment, and chemical manufacturing. They have a maximum operating temperature of 80°C.

Glass Fiber-Reinforced Polypropylene Butterfly Valves (GFPP)

GFPP (Glass-Filled Polypropylene) is an advanced modification of PP that incorporates glass fibers to enhance its rigidity, tensile strength, flexural strength, and dimensional stability. Similar to standard PP valves, GFPP butterfly valves are resistant to chemicals and corrosion. They are designed for more demanding environments and heavy-duty applications.

Polyvinylidene Fluoride Butterfly Valves (PVDF)

PVDF (Polyvinylidene Fluoride) butterfly valves are lightweight and offer exceptional corrosion resistance. They are highly abrasion-resistant, making them suitable for handling media with suspended solids. PVDF valves are ideal for high-purity applications and are compatible with most chemicals, including alcohols, hydrocarbons, and halogenated solvents, which makes them commonly used in chemical manufacturing. They also provide reliable, leak-free handling of substances. The maximum operating temperature for PVDF butterfly valves is 120°C.

Acrylonitrile Butadiene Styrene Butterfly Valves (ABS)

ABS (Acrylonitrile Butadiene Styrene) is a thermoplastic polymer known for its strength, rigidity, and impact resistance. It is commonly used for constructing valve discs and is compatible with housings made from GFPP, PP, and PVC. ABS is relatively cost-effective. The maximum operating temperature for ABS is 60°C.

Butterfly Valve Seats

Butterfly valve seats are classified into two main types: soft seats and metal seats. The temperature ratings of butterfly valves are determined by the material used for the seat.

Soft Seats

Soft seats are crafted from plastic or elastomeric materials known for their low friction and self-lubricating properties. While they typically have lower temperature and pressure ratings compared to metal seats, they are also more cost-effective.


Polytetrafluoroethylene (PTFE)

Polytetrafluoroethylene (PTFE), commonly known as Teflon, is a synthetic fluoropolymer distinguished by its low friction, high durability, and exceptional resistance to chemicals and heat. Its non-toxic properties make it ideal for applications in the food and pharmaceutical sectors. PTFE valve seats operate efficiently in temperatures ranging from -100°F to 450°F.

Reinforced Polytetrafluoroethylene (RTFE)

Reinforced Polytetrafluoroethylene (RTFE) is an advanced form of PTFE that includes 15% glass fiber. This reinforcement enhances the wear resistance and compressive strength of the material. However, RTFE is not suitable for use with hydrofluoric acid or caustic soda due to its reaction with glass. RTFE seats are effective within a temperature range of -320°F to 450°F.

Thylene-Propylene Diene Monomer (EPDM)

Ethylene-Propylene Diene Monomer (EPDM) is a synthetic rubber known for its exceptional elasticity and resistance to abrasion. EPDM valve seats are well-suited for handling acids, alcohols, and alkaline solutions, as well as chlorinated water, bleach, and concentrated sulfuric acid. It is also resistant to ozone, though it should not be used with petroleum-based solvents and oils. EPDM seats are rated for temperatures between -20°F and 230°F.

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Buna-N

Buna-N, or nitrile rubber, is a versatile rubber with high durability and resistance to wear. Buna-N seats are effective for gases, water, fuels, petroleum, and alcohol. However, they are not suitable for use with acetones, ketones, chlorinated hydrocarbons, nitro hydrocarbons, or ozone. Buna-N seats operate within a temperature range of -35°F to 250°F.

Viton

Viton, also known as FKM, is a fluorocarbon elastomer compatible with a wide range of chemicals but is less effective for steam and water applications. Viton seats function well within temperatures from -20°F to 400°F.

Neoprene

Neoprene, or chloroprene rubber, is a synthetic rubber with good flexibility and resistance to greases, oils, fats, and most chemicals, except for strong oxidizers. It is flame-resistant and used in handling refrigerants and in pulp and paper manufacturing. Neoprene’s black color makes it less suitable for utility water in bleached paper production. Neoprene seats operate between -35°F and 225°F.

Metal Seats

Metal seats are preferred for high-temperature applications as they retain strength and rigidity even at elevated temperatures. They also support higher pressure ratings due to their robust nature compared to soft seats.

Inconel

Inconel, a nickel-chromium-molybdenum alloy, is known for its superior mechanical properties and resistance to corrosion, oxidation, and scaling in extreme conditions. Inconel seats can handle temperatures up to 90°F, with grades such as Inconel 625 and 600 being commonly used in metal seat construction.

Stainless

Stainless steel is also an effective material for metal seats, offering a more cost-effective alternative to Inconel while still providing strong performance.


StelliteTM

Stellite is a corrosion-resistant, non-magnetic cobalt-based alloy that includes chromium and tungsten. This alloy can be customized to suit different application requirements. Incorporating Stellite into valve seats has markedly enhanced their strength and longevity, providing substantial improvements in durability and performance.

Nitriding

Nitriding is a heat treatment technique designed to harden metal surfaces through the diffusion of nitrogen. This process is commonly employed for manufacturing valve seats and can be applied to materials such as low alloy steels, aluminum, molybdenum, and titanium. The nitriding process, which typically lasts several hours, enhances hardness, wear resistance, corrosion resistance, and high-temperature performance.

Chapter 5: What are the advantages and disadvantages of butterfly valves?

The Advantages of Butterfly Valves are the following:

  • Butterfly valves have low pressure drop, which benefits the pumping system of the pipeline.
  • Butterfly valves are quick-acting and have a simple operating mechanism. There are various types of automatic actuation systems that can be utilized in operating butterfly valves.
  • Butterfly valves are more compact and have a simpler construction and lighter weight than other valve types. Hence, they generally consume less space and material. This is because they are designed to fit between two pipe flanges. They are cheaper alternatives to globe valves and gate valves. They also require less maintenance.
  • Butterfly valves can operate at a wider range of temperatures and pressures than ball valves. Soft seats can be backed with metal seats to increase their temperature and flame resistance for fire prevention applications.
  • Butterfly valves can handle large fluid flows at relatively low pressures as well as liquids containing suspended solids.

The Disadvantages of Butterfly Valves are the following:

  • Throttling in butterfly valves is limited to low pressure differentials.
  • Butterfly valves have a poor sealing function. Effective sealing is achieved at low pressures.
  • Butterfly valves require high torque during operation.
  • Cavitation and choking are potential concerns in butterfly valves.

Conclusion

  • Butterfly valves are a type of quarter-turn valve that feature a rotating disc element that allows, controls, and obstructs the fluid flow in a pipeline. They are valued for their compact size and simple construction and operating mechanism and for inducing a low pressure drop across the valve.
  • The main components of butterfly valves are the valve body, disc, stem, seat, and operating mechanism.
  • Butterfly valves can be classified according to the number of offsets, which divide them into three classifications: zero offset, double offset, and triple offset butterfly valves.
  • Butterfly valves can have a wafer, lug, double-flanged, or welded connection design. The wafer type is the only connection design that does not allow isolation or end-of-line service.
  • The butterfly valve body must be made from a tough and rigid material to protect its internal components.
  • Butterfly valve seats are categorized according to their material type. Soft seats are made from elastomeric or plastic materials; these have a low coefficient of friction and self-lubricating properties. Metal seats overcome the limitation of soft seats to operate at high temperatures. The material of construction of the valve seats limits the temperature rating of the butterfly valve.

WhaWhat are Butterfly Valves: Types, Mechanisms, Parts & More

1. What is a Butterfly Valve? What are the Working Principles of Butterfly Valves?

A butterfly valve is a quarter-turn rotational device in piping systems that controls fluid flow via a disc rotated by an external mechanism. When the disc coplanar with flow, it fully obstructs; otherwise, it permits partial or complete flow. It takes a 90° turn to fully open, with the disc vertical to flow. This valve regulates flow within large pipe diameters by quarter-turn rotation of a disc, altering pressure for any position. It's called a butterfly valve because it moves like a butterfly's wings. It's like when a butterfly lands and its wings flap up and down in a 90-degree motion.

2. Parts of a Butterfly Valve

The primary elements of a butterfly valve include the body, stem, disc, and seat. The designs of each component varybased on the materials, the type of flow media, the intended purpose, etc.

2.1 Body

The primary structure of the valve provides the central flow passageway and connection points to the piping. It's typically made of robust materials like cast iron, stainless steel, or engineered plastics to withstand the pressures and fluids it will handle. Body styles play a role in how the valve is installed.

2.2 Disc

The heart of the valve is the disc, which rotates to control flow. It is made of various materials, such as metals or polymers, and may be solid or have holes to reduce weight. Concentric and eccentric disc options are most common.

2.3 Stem

The butterfly valve's stem may seem small, but it's crucial. It links the inside disk to the outside handle, enabling the valve to open or close. Without it, the valve would be useless. The stem comes in two designs—wetted and non-wetted—referring to its protection. Non-wetted stems are shielded from corrosive or erosive substances in the line, while wetted stems are not, requiring materials compatible with the flowing media.

2.4 Seat

This is the sealing surface within the valve body where the disc rests when closed. Seats are crucial for a tight seal and are usually made from softer materials like elastomers, PTFE, or similar polymers for leak prevention. Common materials are:

  • Resilient seat: Entirely made of a soft material, providing excellent sealing but potentially more vulnerable to wear from abrasive fluids.
  • Metal seat: This is a very durable design for extreme conditions, but the sealing may not be as perfect as that of a resilient seat.
  • Hybrid seats: Combine elements of both designs for a balance of properties

3. Advantages of Butterfly Valves

3.1 Compact and lightweight

Butterfly valves boast a space-saving, streamlined design and use less material in their construction. This makes them significantly lighter than comparable gate or globe valves, simplifying installation and making them ideal for applications with tight space restrictions.

3.2 Cost-effective

Butterfly valves' simple design and lower material requirements typically translate to lower manufacturing costs compared to other valve types. This cost advantage extends to installation, as their lighter weight and compact design can reduce labor and material needs.

3.3 Low-pressure drop

When fully open, the disc of a butterfly valve sits mainly parallel to the flow path, presenting minimal obstruction. This results in minimal pressure loss for the fluid passing through, potentially reducing energy costs in pumping systems.

3.4 Quick operation

Butterfly valves' quarter-turn operation allows them to quickly change from fully open to fully closed. This makes them invaluable when rapid shutoff is needed or processes require frequent flow adjustments.

4. Disadvantages of Butterfly Valves

4.1 Limited throttling capabilities

The traditional disc design of a butterfly valve isn't ideal for precise flow control, especially at low rates, as the position of the disc can lead to turbulent flow. However, specialized butterfly valves with eccentric disc shapes can improve fine flow control.
 

4.2 Potential for disc wear

Systems with high pressures or abrasive fluids flowing through the valve can accelerate wear on the seat. Material selection and regular maintenance become important factors in the valve's long-term performance in such conditions.

5. Types of Butterfly Valves

Butterfly valves come in several variations, classified primarily by their body connection method and disc closure design:

5.1 Body Connection Design

Wafer-style

The wafer design is most cost-effective variant of the butterfly valve. The wafer type is positioned between two pipe flanges, secured by flange bolts encircling the valve body. Long bolts pass through the entire valve body, connecting the pipe flanges. Sealing between the valve and pipe flanges is achieved using a snugly fitted seal, like an O-ring or gasket, along with a flat valve face on the downstream and upstream sections. This connection design ensures sealing against bi-directional differential pressures and prevents backward flow in systems intended for universal flow.

Lugged-style

The lug-type butterfly valve features threaded lugs positioned on the exterior of the valve body. Pipe flanges are connected to each side of the bolt inserts using two sets of bolts, eliminating the need for nuts. This setup allows one side to disconnect without impacting the other, which is particularly useful for dead-end service applications. Unlike wafer-style valves, lug-type butterfly valves bear the weight of the piping through the valve body.

5.2 Disc Closure Design

The disc closure design significantly influences butterfly valve performance. Understanding the options is critical to selecting the suitable valve for a specific application:

Concentric 

The most common type has a stem running through the centerline of the disk. It is frequently utilized in low-pressure situations.

Eccentric

This design features a stem that doesn't go through the center line but instead goes behind it, opposite the flow. It was created to prevent the disk and seal from touching too soon before fully closing, reducing operational torque and minimizing valve wear. Hence, the design significantly prolongs the valve's lifespan.

In a double offset or doubly eccentric butterfly valve, the stem is positioned behind the disc’s centerline with an extra offset to one side. This double eccentricity design minimizes contact between the disc and seat, occurring only in the final 1-3° disc closure. 

On the other hand, a triple offset butterfly valve (TOV or TOBV), designed for critical applications, shares a similar structure with the double offset valve but incorporates a third offset, which is the axis of disc-seat contact. The seat surface and the ridge of the disc both have a conical shape, ensuring minimal contact before full valve closure. Triple offset butterfly valves are more efficient and endure less wear, often featuring metal seats for a tight seal, making them suitable for higher temperature ranges.

STREAMING provides various types of butterfly valves for every special needs. Check out STREAMING wafer-style, lugged-style, and eccentric butterfly valves.

6. Materials for the Construction of Butterfly Valves

The valve body requires robust toughness and rigidity to safeguard the internal components of the butterfly valve. Similarly, the stem and disc must exhibit these qualities to endure fluid pressures. Metal and plastic are the main materials utilized in the butterfly valves.

6.1 Metals: Stainless steel

Stainless steel is an alloy with elevated chromium content (10.5-30%) and trace amounts of nickel and molybdenum, which boasts exceptional strength, toughness, and resistance to corrosion and weathering. Its corrosion resistance is primarily due to forming a thin, protective chromium oxide layer, which prevents oxygen diffusion into the material's bulk. This layer can reform in case of surface damage, rendering stainless steel self-healing against rust. Additionally, molybdenum contributes to its resistance to pitting corrosion. Thanks to this robust material, stainless steel butterfly valves excel in handling acidic and corrosive fluids across a broad spectrum of pressures and temperatures. 

6.2 Metals: Carbon steel

Carbon steel has a higher carbon content of up to 2.5%. Commonly employed grades for butterfly valves include ASTM A216 WCB (Welded Cast B-grade) and LCC (Low Carbon Content), with WCB suitable for high-temperature environments and LCC for low-temperature conditions. While carbon steel butterfly valves present a cost-effective alternative to stainless steel counterparts, they are not suitable for handling corrosive fluids due to their susceptibility to corrosion.

6.3 Metals: Cast Iron

Cast iron, a ferrous alloy primarily composed of iron, carbon, and silicon, is renowned for its strength, longevity, and heat resistance. Its robustness and resistance to deformation make it ideal for applications subjected to high temperatures and heavy loads. Cast iron butterfly valves, utilizing these features, are commonly employed in water purification, wastewater treatment, food processing, and pharmaceutical manufacturing. However, cast iron is susceptible to corrosion in highly acidic or alkaline environments, which can lead to deterioration over time. Therefore, it is essential to assess the compatibility of cast iron with the specific operating conditions before implementation.

6.4 Metals: Hastelloy

Hastelloy, an alloy comprising nickel, chromium, and molybdenum, was pioneered by Haynes International, Inc. Renowned for its robustness, it maintains high strength even at elevated temperatures. It exhibits exceptional resistance against corrosion, cracking, and oxidizing and reducing agents. Hastelloy butterfly valves are prevalent in industries such as oil and gas processing and power generation, and they are particularly suitable for handling nitric, hydrochloric, and sulfuric acids under moderate temperatures.

6.5 Plastics: PTFE for Soft Seats

Polytetrafluoroethylene (PTFE), commonly called Teflon, is the preferred material for valve seats due to its synthetic fluoropolymer composition. Renowned for its low friction, high resilience, and exceptional chemical and fire resistance, PTFE finds extensive use in various industries, including food and pharmaceutical manufacturing, thanks to its non-toxic properties. Operating seamlessly within a temperature range of -100°F to 450°F, PTFE seats ensure reliable performance across diverse applications.

6.6 Plastics: EPDM for Soft Seats

Ethylene-propylene diene monomer (EPDM) is a synthetic rubber known for its toughness and resistance to wear and tear. EPDM valve seats are versatile and capable of handling acids, alcohols, and alkaline solutions, making them ideal for applications like chlorinated water treatment and handling sulfuric acid. EPDM is also ozone-resistant, but it's important to note its incompatibility with petroleum-based products and turpentine. EPDM seats operate effectively within a temperature range of -20°F to 230°F, ensuring reliable performance across various industries and environments.

7. Common Butterfly Valve Uses

7.1 Water & Wastewater Treatment

Butterfly valves are ideal for handling large volumes of water, slurries, and sludge due to their minimal flow obstruction and cost-effectiveness in large sizes. Their simple operation also makes them easy to manage within complex treatment systems.

7.2 HVAC

Large-diameter butterfly valves offer efficient airflow control in heating, ventilation, and air conditioning systems. Their lightweight and space-saving design simplifies installation within building ductwork.

7.3 Chemical Processing

The wide range of materials, such as stainless steels, plastics, and specialty alloys, and seat options allows butterfly valves to be tailored to specific chemicals and corrosive environments. Their quarter-turn operation is also beneficial in processes where fast adjustments are needed.

7.4 Oil and Gas

Butterfly valves find use throughout the oil and gas industry due to their ability to handle large volumes of fluids and their availability in high-pressure configurations. Robust materials options meet the demands of both exploration and refining operations.

7.5 Power Generation

Butterfly valves effectively control cooling water, steam, and other process fluids in power plants. Specialized high-performance butterfly valves with suitable seals and materials can withstand the high temperatures commonly found in power generation.

7.6 Pulp and Paper

Butterfly valves effectively handle the paper pulp, slurries, and chemicals involved in paper production processes. Materials are carefully chosen to resist abrasion and the specific chemicals used in pulping.

STREAMING - Your Best Butterfly Valve Supplier

If you're looking for high-quality butterfly valves for your industrial needs, look no further than STREAMING. Here's why:

  • Unmatched Quality: Our valves are built to last, delivering dependable performance in even the most demanding applications.
  • Comprehensive Selection: Find the perfect valve for your system with our vast range of designs, materials, and sizes.
  • Expert Support: Our team is ready to guide you through the selection process, ensuring you get the optimal solution for your unique requirements.

Our commitment to quality, extensive product range, and expertise make us a trusted partner. STREAMING has the right solution for your application with various butterfly valve designs, materials, and sizes

Contact us today to learn more and let us help you find the perfect butterfly valves to streamline your operations.

FAQs

What is a butterfly valve used for?

Butterfly valves are versatile flow control devices used in various industries to regulate the flow of liquids, gasses, and slurries. They are commonly found in water treatment, HVAC, chemical processing, oil and gas, and many other applications.

What is the problem with the butterfly valve?

Butterfly valves have two main drawbacks: restricted throttling, making them less than ideal for precise flow control, especially at low flow rates, and susceptibility to wear. Another is susceptibility to wear because high pressure or abrasive conditions can lead to disc wear, potentially compromising sealing effectiveness.

Which is better: butterfly valve or ball valve?

The best choice depends on your needs. 

Our Ball valves offer superior tight shutoff and are better for precise flow control.

If you are looking for more details, kindly visit Hvac Butterfly Valve.