FieldEngineersKitEngineering Reference & ASME Code Basis
1. Core Formula & Variable Definitions
ASME PCC-1 (Guidelines for Pressure Boundary Bolted Flange Joint Assembly) · ASME B16.5 / B16.47 (Flange bolting count & stud size) · ASME B1.1 (Unified Inch Screw Threads) · ASTM A193 / A194 (Alloy and stainless fastener grades)
T = Ttable · (KKref) · fgrade · Kref = 0.13 (moly)
Round 1 = 0.30 T · Round 2 = 0.60 T · Round 3/4 = 1.00 T (star → circular check)
ASME PCC-1 screening lookup · ASME B16.5 stud geometry · rescale by nut factor K
This calculator looks up ASME B16.5 flange stud size and bolt count, then returns a PCC-1-style moly assembly torque T_table (K_ref = 0.13, A193 B7 baseline). Selected lubricant scales torque as T = T_table × (K / 0.13) × f_grade. A193 B8 / B8M Class 2 use f_grade = 0.85; B7 uses 1.00. The Torque & Passes tab shows Round 1–4 at 30% / 60% / 100% / circular 100% of T. The Sequence tab draws clockwise bolt numbering; Joint Details lists NPS, class, studs, K, and T. First-principles T = K · D · Fp is not solved in-app — confirm critical joints against the owner’s PCC-1 appendix.
- T (Target Assembly Torque) — Hero output after K and grade scaling (N·m or ft·lb). Same value labeled Target assembly torque (T) in Joint Details.
- T_table (Tabulated Moly Torque) — Stored PCC-1-style screening torque for moly K = 0.13 and A193 B7 at the selected NPS × class (see Quick Reference and boltTorque.json).
- K (Nut Friction Factor) — Advanced 1.2 presets: moly 0.13, PTFE 0.11, dry / lightly oiled 0.20.
- K_ref (Table Reference Nut Factor) — Fixed 0.13 — the lubricant assumed when T_table was stored.
- f_grade (Bolt Grade Factor) — 1.00 for A193 B7; 0.85 for A193 B8 / B8M Class 2. Annealed B8 Class 1 is not offered.
- N (Number of Studs) — Bolt count from the B16.5 joint row (shown in hero badges and Joint Details).
- D (Nominal Stud Diameter) — Stud size from the same table row (e.g. 3/4" / M20 for NPS 6 Class 300).
2. Allowances, Tolerances & Standards
Round fractions and star sequences match this calculator’s Torque & Passes / Sequence tabs. Torque remains a screening method — verify critical joints per project procedure.
Rounds 1–3 follow the joint star/cross sequence from the data table; Round 4 is a continuous circular check at 100% T until nuts stop rotating.
Changing from moly (0.13) to dry (0.20) raises required wrench torque by ~54% for the same target preload. Applying a moly table value on dry threads under-loads the gasket.
Per ASME PCC-1, studs should fully engage nuts with a few exposed threads for inspection — not computed by this tool.
Align flanges before torquing. Misalignment causes uneven gasket crush and stud bending; outside calculator scope.
Quick Reference Lookup Table
| NPS | Class 150 (N·m) | Class 150 studs | Class 300 (N·m) | Class 300 studs |
|---|---|---|---|---|
| 2" | 135 | 4 × 5/8" | 190 | 8 × 5/8" |
| 4" | 190 | 8 × 5/8" | 340 | 8 × 3/4" |
| 6" | 271 | 8 × 3/4" | 366 | 12 × 3/4" |
| 8" | 340 | 8 × 3/4" | 475 | 12 × 7/8" |
| 10" | 434 | 12 × 7/8" | 824 | 16 × 1" |
| 12" | 434 | 12 × 7/8" | 1098 | 16 × 1-1/8" |
Lookup also covers Class 600 (e.g. NPS 6 Class 600 → 1037 N·m, 12 × 1") and NPS ½"–24". Values match data/mechanical/boltTorque.json. Dry or PTFE rescale T ∝ K/0.13; B8/B8M Class 2 × 0.85. Unit toggle converts the N·m columns to ft·lb.
3. Material & Code Limitations
Grade selection changes allowable preload. This calculator offers B7 and strain-hardened B8/B8M Class 2 only — never apply B7 table torque to annealed B8 Class 1.
| Material Group | Temperature Range | Allowable Stress / Limit | Engineering Notes |
|---|---|---|---|
| ASTM A193 B7 / A194 2H (calculator baseline) | -29 °C to 427 °C (-20 °F to 800 °F) | Sy ≈ 724 MPa (105 ksi); f_grade = 1.00 | Default in Advanced 1.2. All T_table values assume B7 with moly K = 0.13. |
| ASTM A320 L7 / A194 7 (low-temperature) | -101 °C to 343 °C (-150 °F to 650 °F) | Sy ≈ 724 MPa (105 ksi) when impact-qualified | Not a separate dropdown — use B7 outputs only when the project specifies equivalent preload. |
| ASTM A193 B8 / B8M Class 2 (in-app option) | -196 °C to 538 °C (-320 °F to 1000 °F) | f_grade = 0.85 × B7 T_table (e.g. NPS 6 Cl 300 → 311 N·m) | Strain-hardened stainless option in Advanced 1.2. Confirm owner appendix before use. |
| ASTM A193 B8 / B8M Class 1 (annealed — not offered) | -196 °C to 538 °C (-320 °F to 1000 °F) | Sy ≈ 207 MPa (30 ksi) — far below B7 | Do not use B7 or Class 2 calculator outputs on Class 1 studs; they will yield. |
Code Applicability & Safety Boundaries
- Calculator scope: NPS × class table lookup, K scaling, grade factor, Round 1–4 torque targets, and star diagram. It does not solve Fp from σb·As or check gasket Wm.
- For studs about D ≥ 1-1/2" or Class 900+ / critical service, prefer hydraulic tensioning per project PCC-1 appendix.
- Lubricate threads and nut faces. Dry makeup with a moly torque value under-compresses the gasket.
4. Step-by-Step Worked Example
Field VerificationShowHide
Follow the same UI path: select NPS 6 / Class 300, keep moly K = 0.13 and A193 B7, read T from the hero card, then open Torque & Passes for Round 1–4. Finally rescale for dry lubricant (K = 0.20) in Advanced 1.2.
Read tabulated moly torque (T_table)
Hero shows Target Assembly Torque (T) = 366 N·m with badges for K, grade, and studs.
Apply K and grade factors
Switching to B8 Class 2 multiplies by 0.85 → 311 N·m.
Read Round 1–4 on Torque & Passes
Whole-N·m rounding matches formatTorque in the engine.
Rescale for dry lubricant (K = 0.20)
Same preload intent needs higher wrench torque when friction rises.
Export / site confirmation
Hand calc T = K·D·Fp may differ from screening tables — project appendix governs.
5. Frequently Asked Questions & Technical References
ShowHide
ASME B16.5 defines flange dimensions, bolt circles, and stud counts. ASME PCC-1 covers bolted flange joint assembly — nut factors and multi-pass sequences. This calculator combines B16.5 geometry with PCC-1-style screening torques.
Stored torques assume moly K_ref = 0.13. The engine computes T = T_table × (K / 0.13) × f_grade. Dry / lightly oiled uses K = 0.20; PTFE uses 0.11. Using a moly table value on dry threads under-loads the joint.
No. Options are B7 and B8 / B8M Class 2 (0.85× factor). Annealed B8 Class 1 has much lower yield (~207 MPa) — never apply B7 table torque to Class 1 studs.
The app is a table lookup + K/grade rescale, not a live Appendix O solver. Screening tables embed owner-style target stress assumptions. Use the worked example path (NPS 6 Class 300 → 366 N·m) and confirm critical joints against the project PCC-1 appendix.
Torque & Passes — hero T plus Round 1–4. Bolt Sequence Diagram — clockwise numbering and the star/cross text. Joint Details — NPS, class, stud size, count, grade, K, and T.
Prefer tensioning on large studs (about D ≥ 1-1/2"), high classes (900+), or critical services. Tensioners apply axial load without relying on nut factor K.