The ASME B16.5 specification
The ASME B16.5 specification includes NPS 1/2 to NPS 24 Metric / Inch steel pipe flanges and flanged fittings in pressure level 150 to class 2500. This includes measurements of pressure-temperature, components, lengths, tolerances, naming, measuring and methods of designating openings for flanged fittings and pipe flanges. Two very critical flanges are widely used in piping structures such as the weld neck flange and blind flanges. The word “B16.5” or “B16 5” is used for interchangeability, which corresponds to the same standard. Nevertheless, the regular ASME B16 5 (ANSI B16 5) only includes measurements of up to 24 inches. The ASME B16.47 specification includes the specifications for pressure-temperature, components, lengths, tolerances, labeling and inspection of pipe flanges in sizes NPS 26 to NPS 60 and in classification classes 75, 150, 300, 400, 600 and 900 for larger sizes.
Even so, the standard ASME B16.47 is additionally divided into Blind flange and Weld-neck flange ASME B16.47 series A and ASME B16.47 series B flange. In the past the flange of the API 605 was also identified as the Series B flange. The ASME B16.47 Series B flanges require more but smaller fasteners (bolts & nuts) than the Series A flanges and have a smaller diameter of the bolt circle than the Series A.
How do the Series A and Series B flanges differ?
Usually, ASME B16 47 Series A flanges in the same size and pressure level are much larger, heavier and tougher than Series B flanges so they can handle more external load than Series B form. The ASME B16.47 Series B flanges need too much but fewer fasteners (bolts & nuts) than the Series A flanges and have a wider diameter of the bolt loop than the Series A.
Upon mounting the smaller diameter of the bolt circle results in less flange motion. ASME B16.47 Series A flanges are more costly from a business standpoint than ASME B16 47 Series B flanges. Any customers or piping suppliers may choose Series A flanges for the new pipeline or machinery. Even if you do any retrofitting, repair work or non-critical piping design, the Series B flanges are more widely utilized.
Typically, the greater width of the bolt loop produces less flange shift during mounting. All Series A and B describe raised face form welded neck flanges and blind flanges. Moreover, within this layout, Series A explains flanges of the ring type joint (RTJ) from Class 300 to Class 900 whereas Series B does not.
Regular welded cover, slide on, blind flanges etc. Flanges for sizes up to 24 “nominal tubing are secured by regular B16.5. B16.47 type A or B for weld-neck and blind flanges are given in sizes 26” and greater. The Series A flanges are bigger, broader and more costly while the Series B flanges have more bolt holes and are less expensive than the Series A flanges. Both the sequence API605 and B have the same flanges.