The high performance butterfly valve has excellent sealing properties and a tight shut-off. The disc of high performance butterfly valve is an off-center portion of a ball, and the seating function of this valve is identical to that of a ball valve. The disk and seats of the valve are offset from the shaft axis and it is not necessary to seal the shaft in this valve. Many valves have a main seat made of durable plastic and a secondary metal seal making them “fire-safe.” High-performance butterfly valve is produced in pressure groups as high as ANSI 900 and could be used in applications involving a tight shut-off.
How does a high performance butterfly valve Work?
In High-performance butterfly valves, the sealing may be provided by an interference-fit seat or a line-energized seat configuration, where the fluid pressure inside the pipe helps in boosting the interference between the seat and the outer part of the disk. Frequently utilized seat materials are polytetrafluoroethylene (PTFE) or reinforced PTFE (RTFE) due to a greater performance and temperature range.
Metal seats are also available in high-performance butterfly valves. These metal seats allow the use of a butterfly valve at a much higher temperature. Up to a thousand degrees, F. Fire-safe versions are also offered that provides the shut-off of the valve just before the fire, and the metal seal guarantees the closure of the valve during and after the fire.
Double Offset Butterfly Valve: The double-offset butterfly valve also known as the high performance butterfly valve (HPBFV), has two offset valves similar to the concentric butterfly valve. The first offset is the shaft, which is located not in the center of the disk, but behind the disk. This offset would allow the valve to have a continuous sealing surface on the disk.
The second offset is the shaft located not in the middle line of the pipe, but just to the right of the mainline. This arrangement would make the seat feel less pressure than the concentric butterfly valve and therefore prolong its life.
Triple offset Butterfly valve: The triple offset butterfly valve also a high-performance valve is a 3 offset valve compared with the concentric butterfly valve. Like a double offset butterfly valve with 2 offsets, this triple offset also has the same offset except that it has one extra offset and is a conical type seat. This conical-shaped seat would complement the disk that was already made to fit the seat.
This arrangement would mean that the seat does not have pressure or friction when it is closed or opened. As a part of this arrangement, the valve will have a bubble-tight application and a lifetime far longer than the double-off butterfly valve.
When to Use High Performance Butterfly Valves?
High Performance Butterfly valve is a versatile & reliable valve for handling high-temperature and high-pressure conditions and where superior flexible stem packaging is required to manage stem leakage or emissions. Both are for temperatures ranges from 1200 degrees F and pressures ranges to 1440 psi (150-600# ANSI).
They are more costly than RSBFVs, come equipped with Carbon Steel or Stainless Steel (or special alloys like Duplex or Super Duplex SS). They can be powered by actuators, handlers, or gears and are used in fuel management systems, chemical, petrochemical, and offshore industries or where exceptionally long life is necessary. These valves are located by a stop in the body.
Triple offset butterfly valve is found in oil refineries, high-pressure steam and offshore installations where more severe conditions occur and much higher reliable performance and/or longer life cycles are required. The valves are generally rated as 150-900# ANSI (1500# ANSI available) class and are essentially API-607 Fire Protected with a soft seat. They are very effective for serious applications but are more costly than the double-offset butterfly valve.