Triple offset & Metal to Metal Butterfly Valve

Vihung Triple offset & Metal to Metal Butterfly Valve design offers rugged reliability and extremely easy maintenance in the field. These valves are bi-directional with advanced design features such as triple eccentricity and unique elliptical seat geometry, ensuring compressive sealing around the entire seat and a “tight” bubble-free valve. These valves are well suited for operation in light vacuum to high pressure applications. The standard, non-rubbing, metal-to-metal sealing system is inherently fire-safe by design. Triple offset butterfly valve can be used not only on-off but also to regulate the flow. A triple offset butterfly valve (TOV or TOBV) is often used in critical applications and is designed similar to a double offset butterfly valve. The third offset is the disc-seat contact axis. The seat surface takes a conical shape, which, coupled with the same shape at the ridge of the disc, results in minimal contact before full closure of the valve. A triple offset butterfly valve is more efficient and allows for less wear. Triple offset valves are often made with metal seats to create a bubble-tight shut-off. The metal seats allow butterfly valves to be used in higher temperature ranges.

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Triple offset valves outperform traditional valves with increased durability, reliability and lower ownership cost.?The seat of the triple offset valve is designed to minimize wear, provide lower maintenance cost and extend service life.?The ‘zero leakage’ sealing capabilities of triple offset valves provides the performance to keep your processes operating reliably at top efficiency even in extreme operating conditions.?All of these benefits also come with a large weight saving?when compared to many other valves, making for much easier installation and maintenance.

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Triple Offset Design:

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Vihung Triple offset & Metal to Metal Butterfly 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.

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Offset 1

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

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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.

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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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Valves construction:

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Vihung Triple offset & Metal to Metal Butterfly Valve?is a robust valve capable of performing bidirectional zero leakage notwithstanding extreme temperature conditions. Indeed, its all-metal?construction,?inherently fire resistant, is unaffected by temperature changes and a fully integrated long bonnet keeps packing protected from extreme service temperatures (from -60 °C to 450 °C - from -76 °F to +842 °F).Furthermore, the?flange spot facing?ensures flange bolting nut and washer planarity, increases reliability and safety of flanged joints with long term tightness and no re-tightening requirements.

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Sealing components:

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The materials chosen for sealing, coupled with precise machining, significantly contribute to extending the life of the valve. Every Vihung Triple offset & Metal to Metal Butterfly Valve in basic configuration features a smoothly grinded seat with Stellite grade 21 weld overlay highly resistant to galling, abrasion, erosion and corrosion.

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The Vihung seal ring is the key flexible component necessary to perform sealing?and may be?laminated in Duplex (as a minimum) or manufactured as a one-piece solid. Seal rings are easily interchangeable thanks to their self-centering ability and the presence of reference pins that simplify assembly. In addition, a dynamic spiral wound gasket ensures an adequate expansion and contraction of the seal ring during opening and closing.

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Trim:

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Vihung?valves all share the same trim – a combination of optimized angles, and robust bearings and shafts. Our engineers have developed over four decades each and every component to maximize safety

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while keeping an extremely streamlined and functional design:

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The one-piece shaft?maximizes robustness to a level which is not reachable with stub shafts commonly used with low pressure butterfly valves.

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Two-piece packing glands?enhance safety and reliability in terms of fugitive emissions over time.

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The shaft to disc connection?is secured by keys (no pins) to optimize torque transmission without compromising shaft integrity.

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The disc is not a sealing element, only a carrier. Being consistent with body material, the disc can be exposed to the same level of abrasion and corrosion of the valve body without negative effects on tightness and operability.

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Heavy duty bearings and thrust bearing?are designed to withstand high pressure loads and wear.

Standard reinforced, braided and flexible graphite bearing protectors eliminate the risk of particle intrusion, ensure constant torque demand and increase overall reliability.

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Internal and external retaining devices?ensure Vihung?blowout-proof one-piece shaft is safe to operate and provide complete compliance with API 609.

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Open/closed disc references and an external disc position indicator?simplify installation/removal procedures and are in compliance with API 609.

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Features?of Vihung Triple offset & Metal to Metal Butterfly Valve:

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Vihung Triple offset & Metal to Metal Butterfly Valve?basic configuration is available with several options:

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A packing flushing device?is usually added whenever the fluid involves high health & safety risks – through this connection a pressure chamber and/or a suction point can be created to eliminate or intercept any leakage.

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A live loaded mechanism?minimizes the need to tighten the packing whenever the valve is used in heavy duty applications (including thermal cycling) or packing maintenance is not practical.

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Top and bottom bearings can be protected from dirty or polymerizing/crystallizing medium by?flushing devices?which create a barrier by means of a clean fluid injection, providing additional operational safety and reliability.

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A one-piece metal?Solid Seal Ring (SSR)?is chosen whenever the application may negatively affect the life of the standard laminated seal ring. SSRs are a standard feature in high pressure, cryogenic and high temperature configuration.

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Cryogenic configuration:

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Our?cryogenic configuration?has been designed in order to operate with temperatures down to -254 °C (-425.2 °F). The following features differentiate Vihung?Cryogenic triple offset butterfly valve?from the basic configuration:

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Vihung?seal ring is always a one-piece solid in Nitronic??50 (Solid Seal Ring) - a material highly resistant to corrosion able to preserve important mechanical features at low temperatures. Nitronic??50 also has exceptional yield strength, approximately double that of other series 300?stainless steels at ambient temperature.

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An extended bonnet keeps packing protected from cryogenic service temperatures down to -254 °C (-425.2 °F), meeting the requirements of BS6364 for non-cold box applications and major end user specifications.

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Cryogenic valves are available in Double flanged, lug, butt-weld and butt-weld top entry body styles:

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Double flanged body:

The most widely used pipe connection - it enables the best gasket load distribution and short bolting reduces the risk of stretching. The standardized flange design also ensures safe pipe jointing and ease of assembly/disassembly from the line. Vihung?provides ASME and EN flanges including designs to ASME VIII sect 2 div.1.

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Butt-weld body:

The ideal choice whenever flanged connections need to be reduced, this design provides significant initial cost savings. The butt-weld body completely eliminates the possibility of fugitive emissions through flanged joints induced by the adjacent pipe stresses. As for all Vihung?valves, ongoing maintenance is not required.

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Lug body:

A single flange design and more economical than Double flanged, as it requires less material. With threaded inserts on both sides, it is installed using two sets of bolts and no nuts. According to common industry practices, operators tend to avoid using this body style for diameters higher than NPS 36 due to operational difficulties in installing the valve.

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Butt-weld top entry body:

When an inline maintenance capability is mandatory, this design allows for access without removing the valve body from the line. The entire valve trim can be removed from the body and individual valve parts can be accessed in total safety. This feature allows for any unpredictable and extraordinary valve repair, which would be impossible, impractical or unsafe with different valve designs. Overall, the maintenance of a Vihung?valve remains largely unnecessary throughout the product lifecycle.

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High Temperature configuration:

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Our?high temperature configuration?has been designed to operate with temperatures up to 815 °C (1,500 °F). The following features differentiate Vihung?High Temperature butterfly valve?from the basic configuration:

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Vihung?seal ring is always a one-piece solid in different materials depending on the valve body - this ensures no graphite oxidation and weakening, while allowing for various hard facing technologies to be applied in order to respond to application risks.

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A bolted extended bonnet keeps packing protected from high service temperatures up to 815 °C (1,500 °F).

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Bearings and thrust bearing can be hard faced with Stellite or other overlays ensuring high mechanical properties and responding to application risks.

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All materials, including disc bolting, are selected to guarantee suitable mechanical properties in high temperatures and consistent thermal expansion rates.