Lots of variety which makes these suitable for a variety of temperatures and pressures. The offset type can have rubber, polymer (PTFE or other), metal &graphite, or even metal seats. 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. “Offset” type, meaning the shaft is offset from the disc, so it can handle higher differential pressures. These are popular in low-pressure systems (Class 150 or less), relatively lower cycle life, rubber liners are also good for abrasive slurry services. Also known as rubber-lined butterfly valves. Differences between API 609 Category A and Category B Butterfly Valves Category A Butterfly Valves The valve body was modified to the American standard connection size. In the API 609 Category B, the 6-inch to 150LB butterfly valve is specified, the structure length is only 57mm, and many manufacturers, or 70mm, is the same with the national standard valve body, it can be seen that many American standard butterfly valve manufacturers directly to use the national standard valve mold.

This is also a way to judge a manufacturer if they are professional in producing American standard butterfly valves. In comparison with the national standard GB butterfly valve, the flange butterfly valve, and the national standard butterfly valve structure length is the same, but there is a gap between the clip butterfly valve, especially the 6 inch, 8 inch difference between the two specifications/standard is largest. The Class B butterfly valve of the API 609 standard specifies the structure length of the American standard butterfly valve, flange butterfly valve, and lug butterfly valve. Sizes covered are NPS 3 to NPS 24 for Classes 150, 300, and 600. These valves may have a seat rating less than the body rating. Pressure-temperature rated butterfly valves that have an offset seat and either an eccentric or a concentric disc configuration. Sizes covered are NPS 2 to NPS 48 for valves having ASME Class 125 or Class 150 flange bolting patterns.

Manufacturer’s rated cold working pressure (CWP) butterfly valves, usually with a concentric disc and seat configuration. Two butterfly valve categories: Category A Butterfly Valves: Differences between API 609 Category A and Category B Butterfly Valves.

Api 609 category b pdf