Initially, a traditional butterfly valve was used where a close seal was not very necessary. Over the years, with new technology High Performance Butterfly valves (HPBFV) have been developed. These High-Performance Butterfly valves are manufactured with relatively strong seals made of rubber or elastomeric materials that provide strong shut-off compared to other forms of valves. Butterfly valves are used where there are space restrictions. In comparison to gate valves, butterfly valves may be used for throttling or flow control as well as in a completely open and fully closed role. The reduction of pressure through the butterfly valve is minimal relative to the gate valve. Butterfly valves are found in small and large sizes. They can be hand-controlled or operated using a wrench or a gear mechanism.
HIGH PERFORMANCE BUTTERFLY VALVE
Traditional butterfly valves are used primarily in low-pressure water and throttling systems. The seat, the disc, and the shaft are coplanar. The sealing is achieved by an interference fit between the disk and the resilient liner. The power of the seat is constrained by the working torque of the valve and the seal between the shaft and the liner. The sealing properties of this valve are weak and leaks typically occur.
What are High-Performance Butterfly valves?
The high-performance butterfly valve has excellent sealing properties and a tight shut-off. The disk is an off-centre 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 valves are 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 centre 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 (TOV) 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.
TOV’s are 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.
General service vs High-Performance butterfly Valve
- General Service Butterfly Valve: This type of butterfly valve is the default for general applications for processing. They may be used for applications including air, steam, water, etc.
The seat of the valve protects the body to ensure that the products being handled do not come into contact with the body. This seat configuration is suitable for vacuum applications. The valve shaft passes through the disk and is connected to the disk by means of a strong spline, with 3 bushings at the top and bottom serving as a shaft bearing.
The advantages of the general service butterfly valves are that their construction is easier, allowing them to be custom-made to suit various implementations of the pipe operation. Plus, they’re sealed using a range of elastomer forms, and you can pick an elastomer kind that suits your budget.
- High-performance butterfly valves can do anything that the general service butterfly valves could manage, but they are designed to resist liquids and the general service gas valves cannot be accepted. They are made of PTFE seats capable of handling chemically reactive and corrosive liquids, gasses, and steam. Whereas general butterfly valves are made of elastomers that are vulnerable to corrosion, high-performance butterfly valves use resilient material such as graphite to seal the seat. The other benefit is that they range in sizes up to 60 so that they can be used for wider applications.
You will find high-performance butterfly valves made of CS, SS, and other metals. The materials are welded such that the valve can withstand temperatures as low as-320 degrees F and as high as 1200 degrees F and can tolerate pressure ranges up to 1440 PSI. Many high-performance butterfly valves have a stop in the body that stops overtravel and an adjustable packing gland to avoid external leakage.
NTGD is a professional high performance butterfly valve manufacturer, please feel free to contact us if you have any question.