ASME B16.47 Flange Bolting Quick Reference

Large diameter flanges NPS 26–60 | Series A & Series B

How to Use This Chart

ASME B16.47 covers large diameter steel flanges from NPS 26 to 60 in two series: 

•  Series A (formerly ANSI/API 605): Classes 150, 300, 400, 600, and 900 — NPS 26 to 60 (Class 900 listed to NPS 48). 

•  Series B (formerly MSS SP-44): Classes 75, 150, 300, 400, 600, and 900 — NPS 26 to 60 (Classes 400, 600, 900 listed to NPS 36 only). 

For each flange size and class, the table provides:

•  Number of stud bolts for the flanged joint 

•  Nominal stud bolt diameter 

•  Stud bolt length including two heavy hex nuts, for raised-face (RF) flanges 

•  Wrench size (flat-to-flat) for the heavy hex nuts 

Key notes:

•  Stud bolt lengths per ASME B16.47-2020 Tables 31C through 41C. Length includes two heavy hex nuts but excludes end-point chamfer length. 

•  Lengths are for raised face: 0.06 in. RF for Class 75, 150, and 300; 0.25 in. RF for Class 400, 600, and 900. 

•  Series A Class 900 is only listed in B16.47-2020 through NPS 48. Series B Classes 400, 600, and 900 are only listed through NPS 36. 

•  Wrench sizes are for standard heavy hex nuts per ASME B18.2.2. Always verify against project specifications. 

•  For ring-joint (RTJ) facings, stud lengths differ from the raised-face values shown. 

Series A (ANSI/API 605)

Class 150 — Series A  

NPS 26–60

0.06 in. raised face

Class 300 — Series A  

NPS 26–60

0.06 in. raised face 

Class 400 — Series A  

NPS 26–60 

0.25 in. raised face 

Class 600 — Series A  

NPS 26–60 

0.25 in. raised face 

Class 900 — Series A  

NPS 26–48 

0.25 in. raised face 

NPS 50–60 not listed in B16.47 

Series B (MSS SP-44)

Class 75 — Series B  

NPS 26–60 

0.06 in. raised face

Class 150 — Series B  

NPS 26–60 

0.06 in. raised face 

Class 300 — Series B  

NPS 26–60 

0.06 in. raised face 

Class 400 — Series B  

NPS 26–36 only 

0.25 in. raised face 

Class 600 — Series B  

NPS 26–36 only 

0.25 in. raised face

Class 900 — Series B  

NPS 26–36 only 

0.25 in. raised face 

References and Disclaimer 

Data sourced from ASME B16.47-2020 Large Diameter Steel Flanges (NPS 26 through NPS 60) and MY Engineering Bolting Table v1.0. This chart is a field reference only — always verify stud bolt lengths, quantities, and nut dimensions against project specifications, engineering drawings, and the current edition of ASME B16.47 before procuring or installing hardware.