What is the different between API609 Category A and Category B?

API 609 is the American design standard forbutterfly valves, which is divided into Category A and B.

Category A valves are "concentric" type. Also known as rubber lined butterfly valves. These are popular in low pressure systems (Class 150 or less), relatively lower cycle life, rubber liners are also good for abrasive slurry services.

Category B valves are "offset" type, meaning the shaft is offset from the disc, so they can handle higher differential pressures. Most of the offset types cause the disc to rotate freely from the seat after a few degrees of rotation, which minimizes seat wear and increases valve cycle life. The offset type can have rubber, polymer (PTFE or other), metal &graphite, or even metal seats. Lots of variety which makes these suitable for a variety of temperatures and pressures.

The Category B of the API 609 standard specifies the face to face dimension of API butterfly valves, in Wafer end, flange end and lug end. When it comes to compare with the GB standard, FF dimensions of flange end butterfly valve can almost fit each other for both API 609 standard and GB standard.But the dimension is very much different for wafer end butterfly, especially size 6 inch & 8 inch.

The TEKO company has set up a mold designed and manufactured according to API 609. Therefore,all the dimensions includign wall thickness, flange drilling, and face to face can fit the API standards.

For more info, Contact us www.eccentric-butterflyvalve.com