The difference between ASME B16.5 standard and ASME B16.47 standard
ASME B16.5 standard covers steel pipe flanges and flanged fittings from NPS ½” through NPS 24″ in pressure classes 150 to 2500. This includes pressure ratings, dimensions, tolerances, materials, marking, and testing. ASME B16.5 and ANSI B16.5 only cover sizes up to 24 inches. For bigger sizes, ASME B16.47 standard covers pipe flanges in sizes 26″ through 60″ and in pressure class ratings 75, 150, 300, 400, 600, and 900. Then, ASME B16.47 is further divided into ASME B16.47 Series A and ASME B16.47 Series B flanges for blinds and weld necks.
The designation formerly referred to as MSS SP-44 flanges are now considered ASME B16.47 Series A flanges, while API 605 flanges are now ASME B16.47 Series B flanges. Materials covered in this standard are the same as ASME B16.5 except for nickel alloys. Due to this, they share the same pressure-temperature chart for the selection of flange materials.
WHAT IS THE DIFFERENCE BETWEEN ASME B16.47 SERIES A AND SERIES B FLANGES?
ASME B16 47 Series A flanges are thicker, heavier and stronger than their Series B counterparts. They also can often handle more external loading than Series B. Series A flanges tend to be more costly than Series B flanges. ASME B16.47 Series B flanges need more but smaller fasteners, such as bolts & nuts. They also usually have a smaller bolt circle diameter than Series A flanges. Generally, there is less flange movement after installation due to the smaller bolt circle diameter. Both Series A and B define weld neck flanges and blind flanges in raised face type. However, Series A defines ring type joint (RTJ) flanges from Class 300 through Class 900 within this standard while Series B does not.
Series A flanges are popular for new pipeline projects or equipment.Meanwhile,many choose Series B flanges for refurbishment or replacement jobs.