FieldEngineersKitEngineering Reference & ASME Code Basis
1. Formula & conversion factors
ASME B16.5 (Pipe Flanges and Flanged Fittings) · ASME B16.47 (Large Diameter Steel Flanges) — reference only; not tabulated here · ASME B18.2.1 (Square and Hex Bolts and Screws) · ASME B18.2.2 (Nuts for General Applications) — heavy hex
Win = 1.5 · db + 1/8 in (heavy hex nut AF)
Wmm ≈ round-up(Win × 25.4) (nearest metric socket)
Pc = π · BCD / Nbolts
Live values use ASME B16.5 flangeDimension.json rows (stud Ø, N, BCD, tabulated heavy-hex AF).
Field wrench / spanner quick lookup for ASME B16.5 flanges (NPS ½–24). Hero output is heavy-hex nut across-flats (ASME B18.2.2) from the FEK flange table — not commercial standard hex. Stud length starts from the RF table length and applies FF/RTJ deltas. B16.47 NPS 26–60 is not tabulated here.
- d_b (Stud bolt diameter) — Nominal stud diameter from B16.5 bolting table (in / mm).
- W (Heavy hex wrench AF) — Across-flats width of ASME B18.2.2 heavy hex nut; tabulated and checked vs W≈1.5·d_b+1/8".
- N (Bolt count) — Number of flange bolt holes / studs.
- BCD (Bolt circle diameter) — Pitch circle through bolt-hole centers.
- P_c (Circumferential pitch) — Arc spacing between adjacent bolts: π·BCD/N.
- L_stud (Stud length) — Screening stud length for two-flange joint with facing allowance (RF / FF / RTJ).
2. Quick reference lookup table
| NPS | Cl 150 bolts | Cl 150 AF | Cl 300 bolts | Cl 300 AF |
|---|---|---|---|---|
| 2" | 4 × 5/8" | 1-1/16" (27) | 8 × 5/8" | 1-1/16" (27) |
| 3" | 4 × 5/8" | 1-1/16" (27) | 8 × 3/4" | 1-1/4" (32) |
| 4" | 8 × 5/8" | 1-1/16" (27) | 8 × 3/4" | 1-1/4" (32) |
| 6" | 8 × 3/4" | 1-1/4" (32) | 12 × 3/4" | 1-1/4" (32) |
| 8" | 8 × 3/4" | 1-1/4" (32) | 12 × 7/8" | 1-7/16" (36) |
| 10" | 12 × 7/8" | 1-7/16" (36) | 16 × 1" | 1-5/8" (41) |
| 12" | 12 × 7/8" | 1-7/16" (36) | 16 × 1-1/8" | 1-13/16" (46) |
AF = heavy hex across-flats (in) with nearest metric mm in parentheses. Live calculator chart covers all tabulated classes for the selected Class. Stud length adjusts for RF / FF / RTJ.
3. How to use this calculator
- 1
Select NPS and pressure class
Choose the flange NPS and Class (150–2500 as tabulated). Facing (RF / FF / RTJ≥300) adjusts stud length only — not wrench AF.
- 2
Read heavy-hex wrench AF
Hero output is the ASME B18.2.2 heavy hex across-flats from the B16.5 bolting row (imperial AF and nearest metric mm). Do not use commercial standard-hex sizes.
- 3
Confirm stud diameter, count, and pitch
Note stud Ø, bolt count N, BCD, hole diameter, and circumferential pitch P_c = π·BCD/N for field layout and sequence tools.
- 4
Check stud length for facing
Recommended stud length starts from the RF table length with FF/RTJ deltas. Confirm B16.5 Appendix / vendor stud charts before PO.
- 5
Continue to torque and sequence
Open Bolt Torque & Tensioning for target T and Flange Bolt Tightening Sequence for star/circular order using the same NPS / class / bolt count.
4. Engineering FAQ
ASME B16.5 flanges use heavy hex nuts (B18.2.2). Commercial standard hex AF is smaller and will not match the tabulated spanner size.
The app shows the tabulated heavy-hex AF in mm (nearest practical socket). Always check hub clearance before using an impact gun.
No — wrench AF follows stud diameter. Facing mainly changes stud length (FF shorter, RTJ longer vs RF).
Use Bolt Torque & Tensioning for target T, Bolt Tightening Sequence for star/circular order, and Flange Dimension & Weight for OD / T / pair mass.