What is the butterfly valve?
Butterfly valve, also called flap valve, is a kind of regulating valve with simple structure. The butterfly valve that can be used for switching control of low-pressure pipeline medium refers to the closing part (disc or butterfly plate) as a disc, which rotates around the valve shaft to achieve opening and closing. A kind of valve.
Butterfly valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal, and radioactive media. It mainly plays a role of cutting off and throttling on the pipeline. The butterfly valve opening and closing part is a disc-shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment.
The butterfly valve is usually less than 90° from fully open to fully closed. The butterfly valve and the butterfly stem have no self-locking ability. For the positioning of the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of a worm gear reducer can not only make the butterfly plate self-locking and stop the butterfly plate at any position, but also improve the operating performance of the valve.
Industrial butterfly valve features: high temperature resistance, high applicable pressure range, large nominal diameter of the valve, the valve body is made of carbon steel, and the sealing ring of the valve plate uses a metal ring instead of a rubber ring. Large high-temperature butterfly valves are manufactured by welding steel plates, and are mainly used for flue ducts and gas pipes for high-temperature media.
Design Standards & Scope of Application
Butterfly valves can be designed and manufactured in accordance with a variety of major standards and Codes including:
GB/T 12238 (Flanged and wafer resilient seal butterfly valves),
API 609 (Butterfly valves: Double Flanged, Lug- and Wafer-Type),
BS 5155 (Specification for butterfly valves),
ISO 5752 (Metal valves for use in flanged pipe systems — Face-to-face and centre-to-face dimensions),
ISO 10631 (Metallic butterfly valves for general purposes),
MSS SP-67 (Butterfly Valves),
MSS SP-68 (High pressure butterfly valves with offset design),
JIS B 2032 (Wafer type rubber-seated butterfly valves),
JB/T (Metallic sealing butterfly valve), etc.
Butterfly Valve Classifications
Butterfly valves can be divided into four types according to their construction: center line-type butterfly valves, single-eccentric center butterfly valve, double-eccentric center butterfly valve and three-eccentric center butterfly valve. Center line-type butterfly valve, which the butterfly plate rotation center is located in the center of the valve body, butterfly valve is located in the butterfly plate seal part. Double offset butterfly valve is the popular butterfly valve. This valve has two off-center stems. The first offset is that the axis of the shaft is behind the center line of the disc sealing point. The second offset is that the axis of the shaft is off the center of the valve. The three eccentric butterfly valves have three offsets. Two of these are placed in positions similar to the double-offset butterfly valve, and the third offset is the geometry of the seat surface, resulting in the conical shape of the disc and seat. The cone Angle and two eccentric shaft offsets allow the disc to seal frictionless on the seat.
Butterfly valves can also be classified according to different form of sealing. The first is forced sealing butterfly valve include two types: A. elastic sealing butterfly valve. Seal pressure is produced by the disc squeezing the seat when the valve is closed and the seat or disc is resilient; B. Torque sealing butterfly valve. The seal pressure is generated by the torque applied to the valve shaft. The second is pressure seal butterfly valve. Which the seal pressure is caused by the charging of the cartridge seal element on the seat or disc. The last is self-sealing butterfly valve. The seal pressure is generated automatically by the medium pressure.
Butterfly valves classification according to the different seal material: soft-seal butterfly valve and hard sealing butterfly valve. Soft-seal butterfly valve, which the sealing pair is composed of nonmetallic soft material and nonmetallic soft material. Sealing material using soft material such as: rubber, polytetrafluoroethylene, etc.. This kind of seal sealing performance is better, but not resistant to high temperature, easy to wear, mechanical poor. Hard sealing butterfly valve refers to the sealing material is made of metal: copper seal, stainless steel, nickel base alloy. Seat seal surface layer surfacing welding temperature and corrosion resistant alloy material. This kind of butterfly valve sealing performance with high temperature resistance, light operation, open and close without friction, improve the sealing performance of the butterfly valve, and extend the service life.
Butterfly valves classification according to the operating temperature: high temperature butterfly valve, t>450°C; medium-temperature butterfly valve, 120°C <t <450°C; normal temperature butterfly valve, -40°C <t <120°C; low temperature butterfly valve, -100°C <t <-40°C; cryogenic butterfly valve, t <-100°C.
Butterfly valves type classified by the working pressure: vacuum valve, working pressure is lower than standard atmospheric heap; low pressure valve, nominal pressure PN<1.6MPa; medium pressure valve, nominal pressure is 2.5–6.4MPa; high pressure valve, nominal pressure is 10.0–80.0MPa; super high pressure valve, nominal pressure PN> 100MPa.