ASME B16.47 Series A Blind Flange Dimensions: Class 150 to 900 (NPS 26 to 60)

Series A of ASME B16.47 covers large diameter flanges from NPS 26 to NPS 60. Above NPS 24 the ASME B16.5 table stops, and buyers who carry a B16.5 habit into a 30 inch line find that the bolt circle, the bolt count and the stud length all change with pressure class. The five tables below give the complete Series A blind flange set, Class 150 through Class 900.

 

Dimensions are millimetres except bolt hole and bolt diameter, which are inches in the standard and reproduced here as inch fractions.

 

Two stud lengths are given where the standard allows both a raised face and a ring joint facing: the first column is for the raised face, the second for the ring joint. An ellipsis means the standard does not tabulate that combination and the length is derived from Nonmandatory Appendix D.

Class 150 Blind Flange (NPS 26 to 60)

Class 150 is the one grade in this set where the datasheet tabulates a single stud length and does not carry a separate ring joint value; where the ring joint column is blank, the length is not listed and has to be derived. From Class 300 upward both columns are given.

Class 300 Blind Flange (NPS 26 to 60)

Class 400 Blind Flange (NPS 26 to 60)

Class 600 Blind Flange (NPS 26 to 60)

Class 900 Blind Flange (NPS 26 to 60)

Where the Series A Numbers Diverge From B16.5

Three differences catch out buyers moving from small to large diameter flanges:

• Bolt circle grows faster than flange OD. From NPS 26 to NPS 60 in Class 150 the flange OD rises from 870 mm to 1 854 mm while the bolt circle rises from 806.4 mm to 1 759.0 mm, so the rim left outside the bolt circle stays roughly constant rather than growing.
• Hole count jumps at specific sizes. Class 150 runs 24 holes at NPS 26, 28 at NPS 28 to 32, then 32, 36, 40, 44, 48 and finally 52 holes at NPS 60; the jump points differ by class, so a Class 300 flange at the same size will not necessarily carry the same hole count.
• Stud length is class specific. Class 150 uses L = 225 mm at NPS 26, while Class 900 uses 465 mm at the same size, because the flange thickness and the bolt diameter both increase.

Facing: Raised Face or Ring Joint

Every table carries two stud length columns. The raised face column applies to a 1.6 mm raised face on Class 150 and 300, and to a 6.4 mm raised face on Class 400 and above; the ring joint column applies when the flange is machined for a ring gasket. Mixing the two on one line is the single most common cause of a stud that is too short to develop full thread engagement.

Minimum flange thickness, tf, is given without the raised face height added. A purchase specification that quotes tf as the finished thickness will produce a flange that is thinner than the standard allows once the facing is machined.

The source datasheet can be downloaded here: ASME B16.47 Series A blind flange PDF. Matching large diameter flanges and gaskets are quoted against these tables; send the line list with size, class and facing for a fit-up review.

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