The NVF Triple Offset butterfly valve provides a bi-directional bubble tight shut-off. This geometry ensures that the disc seal contacts the body seat only at the final shut-off position without rubbing or galling, providing a torque generated resilient seal with sufficient “wedging” to ensure a uniform seal contact.
| THE TRIPLE OFFSET GEOMETRY |
| OFFSET 1 | The shaft is offset behind the seat axis to allow complete sealing contact around the entire seat |
| OFFSET 2 | The shaft centerline is offset from the pipe and valve which provides interference free opening and closing of the valve |
| OFFSET 3 | The seat cone axis is offset from the shaft centerline to eliminate friction during closing and opening and to achieve uniform compressive sealing around the entire seat. |
Friction Free Sealing For Long Cycle Life
 NVF provides an extra rigid retaining ring with bolting, resulting from ASME stress calculations. (1) Seat is hardfaced with Stellite as standard. (2) The gasket is spiral wound SS/Graphite for zero leakage | THE LAMINATED DISC SEAL
Seating forces are generated by the torque during closing uniformly around the entire circumference. The resilient seal flexes and energizes, assuming the shape of the seat. The compression forces equally distributed around the perimeter provide a tight bi-directional shut off. The resiliency of the seal allows the valve body and disc to contract or expand, without the risk of jamming due to temperature fluctuations. It is self-adjusting.
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From: valve knowledge
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