The Comprehensive Guide to Triple Offset Butterfly Valves

triple offset butterfly valves

Introduction: What is a Triple Offset Butterfly Valve?

A triple offset butterfly valve is a specialized type of butterfly valve that offers optimal seal ring performance, extended service life, and low maintenance requirements. This type of valve is utilized in various industrial applications, ranging from water treatment, chemical processing, oil and gas, and HVAC systems, to name a few. In this comprehensive guide, we will discuss the features, benefits, and applications of triple offset butterfly valves, as well as compare them to other butterfly valve types.

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How Does a Triple Offset Butterfly Valve Work?

A triple offset butterfly valve operates using three distinct offsets:

• The first offset involves the valve stem’s position, which is eccentric to the centerline of the bore.
• The second offset is the deviation of the disc/seat sealing surface from the shaft’s centerline.
• The third offset involves the conical geometry of the sealing surfaces, which produces a right-angle cone shape.

This unique design ensures a bubble-tight shut-off, metal-to-metal seal, and efficient operation, even under high pressure applications and high-temperature conditions. The working mechanism of triple offset geometry relies on contact pressure rather than elastic deformation, resulting in minimal friction between the sealing components and a longer service life.

butterfly valves

The benefits of Triple Offset Butterfly Valves

Triple offset valve offers several key benefits that make them a preferred choice in various industries:

• Extended Valve Life: The unique sealing design ensures repeatable sealing, resulting in a longer valve lifespan.
• Zero-Leakage Performance: The metal-to-metal seal guarantees a tight shut-off, eliminating any leaks.
• Suitable for Harsh Environments: These valves are corrosion-resistant and ideal for handling harsh media.
• Friction-Free Operation: The design allows for smooth stroking and lower torque requirements, making them suitable for automation.
• Cavity-Free Design: There are no spaces for debris to accumulate, reducing maintenance costs and ensuring uninterrupted operation.

Considerations When Choosing Triple Offset Butterfly Valves

When selecting a triple offset butterfly valve for a specific application, it’s essential to consider the following factors:

• Pressure and Temperature Ratings: Ensure that the valve is designed to withstand the operating pressures and temperatures of the system. Triple offset butterfly valves are available in various pressure classes, ranging from class 150 to class 1500.
• Material Selection: The valve materials should be compatible with the process fluid and surrounding environment. Corrosion-resistant alloys are commonly used for both the disc and seating surface in triple offset valve to ensure zero leakage performance.
• Actuation: Choose an appropriate actuator for the valve, considering factors such as actuation speed, torque requirements, and control options (manual, pneumatic, electric, or hydraulic). The friction-free stroking of triple offset butterfly valves allows for the use of lower torque actuators, making them ideal for automation.
• Size and Connection Type: Select the correct valve size and end connection type (flanged, wafer, or lug) to match the system requirements and ensure proper installation.
• Certifications and Standards: Ensure that the valve meets relevant industry standards and certifications, such as API, ASME, ISO, and CE.

butterfly valves

Triple Offset Butterfly Valve vs Other Offset Type Butterfly Valves

Triple Offset vs Double Offset Butterfly Valves

While both the triple offset and double offset butterfly valves are designed to minimize friction and improve sealing components performance, there are some key differences between the two:

• Seal Type and Friction: Double offset valve relies on plastic deformation for sealing, requiring soft materials for the valve seat. In contrast, triple offset valve maintains metal-to-metal seals with contact pressure, eliminating friction altogether.
• Fluid Service: Double offset valves are suitable for clean fluids only, whereas triple offset valves can handle both clean and dirty fluids due to their sealing mechanism.
• Applications: Triple offset valves are more suited to high-demand operational scenarios, while double offset valves can serve in various industrial applications, such as water treatment, chemicals, oil and gas, and HVAC.
• Cost: Triple offset valves are generally more expensive than double offset valves due to the specialized machining required for their superior sealing performance.

Triple Offset vs Single Offset/Concentric Butterfly Valves

Comparing triple offset butterfly valves to single offset or concentric butterfly valves highlights the following differences:

• Seal Type: Single offset valves use soft materials for the valve seat and rely on friction for seal ring, while triple offset valves utilize metal-to-metal seals with contact pressure.
• Seat Friction and Lifespan: Triple offset valves have a longer operational life due to reduced seat friction, while single offset valves are more susceptible to wear.
• Pressure Class Rating: Triple offset valves can achieve higher pressure class ratings (up to class 1500) compared to single offset valves, which are limited to class 150.
• Fluid Service: Triple offset valves are more tolerant of dirty fluids, while single offset valves are only effective with clean fluids.
• Applications: Triple offset valves are suitable for severe service and high cyclic operations, whereas single offset valves are commonly used in utilities and domestic applications.

Here is an Excel table comparing Triple Offset Butterfly Valves with other offset type butterfly valves:

Triple OffsetDouble OffsetSingle Offset/ConcentricSeal Type and FrictionMetal-to-Metal SealPlastic DeformationFriction Seal with Soft MaterialsFluid ServiceSuitable for both clean and dirty fluidsSuitable for clean fluids onlySuitable for clean fluids onlyApplicationsHigh-demand operational scenarios (water treatment, chemicals, oil and gas, HVAC)Various industrial applicationsUtilities and domestic applicationsCostGenerally more expensiveLess expensiveLess expensiveSeat Friction and LifespanReduced seat friction, longer operational lifeModerate seat friction, moderate operational lifeHigher seat friction, shorter operational lifePressure Class RatingUp to class 1500Up to class 150Up to class 150

This table provides a comparison between triple offset butterfly valves and other offset type butterfly valves, highlighting the differences in seal type, fluid service, applications, cost, seat friction and lifespan, and pressure class rating.

Installation, Maintenance and Repair of Triple Offset Butterfly Valves

Proper installation, maintenance, and repair practices are vital to ensure the optimal performance and longevity of triple offset butterfly valves. Some guidelines to follow include:

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• Installation: Ensure that the valve is installed in the correct orientation, with the disc in the fully open position before installing the actuator. Follow the manufacturer’s recommendations for flange bolting and gasket installation. Always use a gasket compatible with the process fluid and operating conditions.
• Periodic Inspection: Regularly inspect the valve for signs of wear, corrosion, or damage. Monitor the valve’s performance, looking out for issues such as leakage, excessive actuator torque, or difficulty in operation.
• Maintenance: Perform routine maintenance as recommended by the manufacturer, including cleaning, lubrication, and calibration. Replace worn or damaged components as needed.
• Repair: Consult the manufacturer’s guidelines for repair procedures and use genuine replacement parts. If required, seek assistance from qualified service personnel or the valve manufacturer.

butterfly valves

Sustainability and Environmental Benefits of Using Triple Offset Butterfly Valves

Triple offset butterfly valves offer several sustainability and environmental benefits compared to other valve types:

• Reduced Energy Consumption: The friction-free operation of triple offset butterfly valves allows for the use of lower torque actuators, leading to reduced energy consumption during valve actuation.
• Longer Service Life: The contact pressure sealing mechanism and absence of cavities in triple offset valves result in extended valve life, reducing the need for frequent replacement and associated waste.
• Leak Prevention: The tight shut-off performance and metal-to-metal seals of triple offset butterfly valves minimize the risk of fluid leaks, which can lead to environmental contamination and increased emissions.

By choosing triple offset butterfly valves for appropriate applications, industries can contribute to a more sustainable and environmentally friendly approach to valve selection and system design.

Conclusion

Triple offset butterfly valves offer many advantages over other types, such as better sealing, longer lifespan, and lower maintenance. They are widely used in various industries. When choosing these valves, consider factors like pressure and temperature ratings, material compatibility, and size. Proper installation, maintenance, and repair are crucial for optimal performance. These valves also help in sustainability by reducing energy consumption and preventing leaks. To explore the full potential of triple offset butterfly valves, visit our website at https://www.dombor.com/industrial-valves/butterfly-valves/triple-offset-butterfly-valves/ and elevate your industrial processes.

The Vanessa Series 30,000 valve shares the same cone-to-cone principle with a globe valve, but sealing is performed by quarter turn rotation. TOVs use a sealing system consisting of a stationary seat and a rotating sealing surface sharing an identical shape: an inclined conic section. When these cones overlap, closed position is reached and sealing occurs. Such 'quarter turn globe' concept is made possible by the use of three 'offsets' meant to completely eliminate rubbing. Optimized seating angles and rotational characteristics guarantee superior tightness via an ingenious combination of the triple offset design and a flexible metal seal ring across all basic, cryogenic and high temperature configurations.

Offset 1

The shaft is placed behind the plane of the sealing surface to provide a continuous seat path.

Offset 2

The shaft is placed to one side of the pipe/valve centerline to allow the displacement of the seal from the seat during the 90° opening.

Offset 3

The seat and seal cone centerlines are inclined in respect to the pipe/valve centerline. This third offset completely eliminates rubbing.

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