Vanessa's Exclusive Triple Offset Design
Our triple offset valve, also known in the industry as triple eccentric or triple offset butterfly valve, represents an important step forward compared to traditional process valves, such as gate, ball, globe and plug valves. Although Vanessa shares the same cone-to-cone principle with a globe valve, sealing is performed by applying quarter turn rotation instead.
Three offsets against the symmetrical axes of the pipe / valve eliminate any possibility of rubbing:
The shaft is placed behind the plane of the sealing surface. The purpose of this offset is to have a continuous seat path.
The shaft is placed to one side of the pipe / valve centerline. The purpose of this offset is to allow the displacement of the seal from the seat during the 90° opening.
The seat and seal cone centerlines are inclined in respect to the pipe / valve centerline. This third offset completely eliminates rubbing.Vanessa’s seating and rotational characteristics guarantee superior tightness. They derive from an ingenious combination of the triple offset design and the use of a flexible metal seal ring. These key features are at the core of our Series 30,000 and are shared across all configurations, i.e.: Basic, Cryogenic and High Temperature.
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Vanessa's seating force is generated by externally applied torque rather than by mechanical interference as in position-seated ball, butterfly and plug valves. This means that the cone-to-cone sealing occurs by contact pressure and not by friction generated by the elastic deformation of the seat. This feature allows our valve to handle high pressure classes and provide reliable and highly controlled operating torque. Our trim design, seating angles and surface finish all contribute to a very low, consistent and predictable torque demand which is unaffected by fluid temperatures and pressures throughout the valve life. The non-rubbing rotation ensures low and constant running torque across the 90 degree rotation so that the operating torque calculated and tested on a newly manufactured product is equal to a comparable fully operational valve.
Metal to metal
Vanessa's cone-to-cone concept requires metal-to-metal seating in order to handle all possible applications. We use Stellite® grade 21 seat and a resilient seal ring in Duplex as a minimum with high mechanical resistance. Stellite®21 is a cobalt alloy that coats the body seat to provide hardness, resistance to fluid abrasion and wear, while ensuring high corrosion resistance. Due to its unique design, the metal seal ring has elastic properties which allow for radial compression to be uniformly distributed around the seating surface. These are key contributors to the zero leakage performance of the valve.Stellite® is a registered trade name of Deloro
Thanks to sealing elements that remain in position and rotate around their own axis, Vanessa valves allow customers to save valuable space and significantly improve operability due to lower and more consistent running torque compared to any other rising stem valve. Furthermore, the quarter turn rotation eliminates any negative effects on packing caused by rising stems, such as extrusion and abrasion, improving valve performance and reducing fugitive emissions.
No contact between sealing elements during open-close operations
Eliminating contact between seat and seal during opening-closing means extending the life of the sealing elements and the valve altogether. This also combines with the main feature of quarter turn rotation, i.e. low and consistent running torque, for which valve operation remains quick and easy over time and modulating is possible even at very low angles. This feature makes the triple offset valve the ideal solution for any application requiring emergency shutdown, blow off or frequent cycling (e.g. molecular sieve).