As we see description for triple offset butterfly valve from end user's requrest that Category B and also Series B, actually they are different .
It is the one kind of face to face length, in the API 609 ( LUG, Wafer and double flange end butterfly valve) design standard, the face to face length has been specified, divided into Category A and Category B, generally category A refers to the face to face length of the concentric butterfly valve, Category B value is the face to face length of the offset ( eccentric ) butterfly valve.
It is the one kind of flange dimension. series B is mentioned in standard ASME B16.47, which is a flange dimension standard. The flange size of the American standard butterfly valve is usually ASME B 16.5 below 24 inches. There is only one system in this standard. Starting from 26 inches, the flange standard ASME B16.47 is used. There are two type dimensions in ASME B16.47 : Series A and Series B .
The flange sizes of the two series are different, including the outer diameter of the flange, the diameter of cernter of bolt hole, the number of holes, the diameter of the hole, and the thickness of the flange. So the price of the two is different. Usually, Series B flange weight will be lighter than Series A, so the cost of the valve with flange series B will be lower.
Zhejiang Zhengfeng Valve company is a professtional triple offset butterfly valve manufacturer, we can produce flanged butterfly valve with series A and series B .
Zhejiang Zhengfeng Valve