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Getting To Know Better the Triple Offset Butterfly Valves

Triple offset butterfly valves or TOV, also known as triple eccentric butterfly valves, were introduced to the global industry more than fifty years ago. This high-performance (HP) butterfly valves have continued progressing through the years. At the same time, the utilization of these tools has expanded over time across multiple sectors worldwide.

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Valves were generally modeled for water regulation applications. However, model enhancements over the years put all-around valves among other industry essentials for performance in the hardest conditions of hazardous operations. In the same manner, these valves have particular parameters wherein they can operate efficiently.

In the present day, TOVs propose countless advantages to industries they are needed. And they have gained attention recently because of what they can portray in controlling fugitive emissions. Through improved structures, TOVs are used in multiple ways that were never seen before while being used more cost-effectively.

Unraveling the Structure of Triple Offset Butterfly Valve

A triple offset butterfly valve may be the right solution whenever a tight shutoff is necessary. As its name denotes, three distinct offsets are styled into the valve. They are as follows:

  • 1st Offset – applies to the centerline of the seat or disc sealing surfaces, which provides a continuous sealing surface.
  • 2nd Offset – pertains to the location of the shaft for the centerline of the bore. This enables a camming action of the disc to minimize rubbing and wear between the seat and seal.
  • 3rd Offset – is the axle of the seat cone angle that is offset from the centerline of the valve bore to eliminate rubbing of the seal or seat contact surfaces during the process and to preserve sealing integrity over the cycle life of the valve. 
Triple Offset Butterfly Valve

Image Source: https://www.pinterest.ph/pin/202873158192988883/

In most cases, TOVs are chosen for particular applications due to their sealing and economic features compared to other metal-seated valve types. Their compatibility and lightweight structure allow TOVs to be installed and operated efficiently. Plus, they need less pipe bracing. A substitutive seal ring that permits an easy and quick repair and the TOVs low torque would even mean more economical.

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Furthermore, TOVs present a bi-directional tight shutoff with a metal seat only available with soft-seated valves. On this note, they are massively expanding application possibilities. The inventive self-centering, the flexible seal rings, and the optimal torque transmissions – these would mean that TOVs can offer fire-safe models that can be better than the most substantial temperature range of a general butterfly valve model.

Traditional Triple Offset Butterfly Valve

Triple offset butterfly valves can be found traditionally in the following industries:

  • oil and gas processing
  • chemical and petrochemical plants
  • refining
  • power generation
  • district heating
  • pulp and paper
  • water and wastewater treatment
  • offshore platforms
  • steel mills
  • sugar mills

Modernized Triple Offset Butterfly Valve

TOVs utilization in all industries has amplified that resulted in more significant production demands. This case compelled users to seek for solutions that are effective as they are efficient. 

Immense utilization is also on uphill because the features of TOVs offer many benefits to all applications. Some of the benefits are: 

  • operational efficiency, 
  • resistance to abrasive elements and chemicals up to a specific pressure or temperature, and 
  • versatility between numerous operating conditions. 

In taking advantage of former TOV design features, the next generation proposes such features that further improve valve performance and safety, including:

Metal-to-Metal Sealing

TOV can deliver reliable and bi-directional zero leakage at high temperature, high pressure, and harsh service applications. It offers a precision-machined metal seat and seal ring. Also, the metal-to-metal seat can better manage thermal fluctuations. 

Besides, the standard right-angle cone model of TOV supports low-friction and in-line sealing. In hydrocarbon service, the metal-to-metal seat lets a valve to satisfy the requirement for fire-safe applications that are supported by TOV’s rotational motion attribute.

Optimized Seat Angle

The TOV seat angle style associated with Stellite in the valve body seat effects a longer seal life of the valve. It also improved in abrasion resistance, even after extensive cycling. This optimized seat angle can minimize the binding of the disc.

Torque Seating

The torque-seating in a TOV permits the valve to evenly self-adjust in distributing seal compression. An extensive seal ring-supporting gasket and a floating seal ring provide a superior seal and zero leakage. A minimal increase in torque produces a better seal. This is due to more equally disseminated compression of the seal ring alongside the sealing area. Also, the applied torque assures a bi-directional seal.

Shaft Design

The positioning of the pin at the lower part of the disc permits an excellent performance in thermal expansion and diminishes shaft deflection. Hence, allowing a longer valve life expectancy. 

In the present, high-performance butterfly valve manufacturers are altering the traditional design of TOVs and are combining basic features with new ones. This innovation increases its capabilities, allowing TOVs to cater to more detrimental applications and environments. With the association of these new type features, indeed, TOVs can sustain high-temperature steam applications, fire-safe applications, and emergency shutdown services.

Conclusion:

In summary, triple offset butterfly valves have an extensive range of applications, the reason why they are industry essentials. The associated three-part offset valve promotes zero leakage, compactibility, lightweight, and economical. Still, TOVs yields efficient and effective utilization even to rigorous processes.

Resources: www.valvemagazine.com/magazine/sections/back-to-basics/10233-triple-offset-butterfly-valves-3.html

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