Why is sling angle limited to 60° from vertical?

Angles above 60° produce large lateral loads and buckling risk outside this pad-eye screen. Use a spreader / lifting beam and a stamped BTH-1 design.

Is the weld check one-face or both-face?

This app models both-face fillet welds along the lug base (A_w = 2 · 0.707 · w · L), which is standard pad-eye practice.

Does Pass mean I can lift without further review?

No. Pass is a field screening result only. Confirm ASME B30.20, site lift plan, shackle OEM charts, and qualified engineering before the lift.

Lifting Lug & Rigging Capacity Calculator (ASME BTH-1 / AISC) — 50 t · 4 lugs · 45° · S355

Engineering Reference & ASME Code Basis

1. Core Formula & Variable Definitions

ASME BTH-1-2023 — Design of Below-the-Hook Lifting Devices (Chapter 3 lug / pin) · AISC Steel Construction Manual 15th Ed. — Connections / lug plate practice · ASME B30.20-2021 — Below-the-Hook Lifting Devices · AWS D1.1 — Structural Welding Code — Steel (fillet weld sizing)

P_t = W_lift·IF / (N·cos θ) · P_s = P_t·sin θ

σ_b = P_t/(D_pin·t) ≤ 1.25 F_y/N_d · τ_tear = P_t/(2·a·t) ≤ 0.40 F_y/N_d

τ_w = √[(P_t/A_w)² + (P_s·h/S_w)²] ≤ 0.30 F_EXX

ASME BTH-1-2023 Category B (N_d = 2.0) · AISC lug practice · AWS D1.1 fillet · ASME B30.20 below-the-hook

Standard ASME BTH-1Category B · Nd = 2.0Hero W_safe / lugθ max 60° from vertical

θ is sling angle from vertical (0–60°). Edge distance a = R_outer − D_hole/2. Weld throat uses both-face fillets: A_w = 2·0.707·w·L and S_w = 0.707·w·L²/3. Screening only — not a stamped BTH-1 / B30.20 design package.

W_lift (Total lift weight) — Static load to lift (kN or kip), before impact factor.
IF (Dynamic impact factor) — Multiplier on W_lift for dynamic / snatch effects (typically 1.0–2.0).
θ (Sling angle from vertical) — Angle between sling and vertical; limited to ≤ 60° in this screen.
N (Number of acting lugs) — Load-sharing pad eyes (1, 2, or 4).
P_t, P_s (Tension and shear per lug) — P_t = W·IF/(N·cos θ); P_s = P_t·sin θ.
σ_b (Pin-hole bearing stress) — P_t / (D_pin · t) compared to 1.25 F_y / Nd (BTH-1 Category B).
a (Edge distance) — a = R_outer − 0.5·D_hole for tear-out shear path.
τ_w (Combined fillet weld stress) — √[(P_t/A_w)² + (P_s·h/S_w)²] ≤ 0.30 F_EXX (both-face fillet).

2. Screening rules & default duty (Category B)

Default metric duty: W = 150 kN, IF = 1.15, 2 lugs, θ = 30°, S355 plate 25 mm, hole 42 mm, pin 38 mm, both-face 12 mm fillet × 160 mm. Pass when bearing, tear-out, and weld unity ≤ 1.0 and θ ≤ 60°.

Design factor Nd2.0 (Category B)

Pin bearing allowable = 1.25 F_y / Nd; tear-out allowable = 0.40 F_y / Nd.

Sling angle0° ≤ θ ≤ 60° from vertical

θ > 60° fails this screen — use a spreader / lifting beam and stamped BTH-1 design.

Pin clearanceD_hole − D_pin ≤ 5 mm (0.2 in)

Larger clearance may require BTH-1 local stress concentration review (Eq. 3-48 class).

Out of scopeStamped lift plan / B30.20 device cert

Fatigue, fracture toughness at low temperature, spreader beams, and OEM shackle charts are not certified here.

Quick Reference Lookup Table

Illustrative ASME BTH-1 / AISC lifting-lug duties (this app — engine assert)
Case	P_t / lug	Governing notes
15 t · 2 lugs · 30° · S355 · t 25 mm · pin 38 mm	99.6 kN	Pass · weld unity 75% · W_safe/lug ≈ 100 kN
50 t · 4 lugs · 45° · S355 · t 40 mm · pin 60 mm	212.1 kN	Pass · σ_b 88.4 MPa / allow 221.9 MPa
30 kip · 2 lugs · 0° · A36 · t 0.75 in · pin 1.25 in	17.25 kip	Pass · σ_b ≈ 18.4 ksi
100 kip · 4 lugs · 30° · A572-50 · t 1.5 in · pin 2 in	36.1 kip	Pass · weld governs · W_safe/lug ≈ 33 kip

P_t = W·IF/(N·cos θ). Weld model is both-face fillet at the lug base. Values are from the calculator engine, not LLM placeholders.

3. Applicability & structural steel service limits

Ambient structural carbon steels (S275 / S355 / A36 / A572 Gr.50 / SA-516 Gr.70) with Category B Nd = 2.0. Not temperature-derated ASME Section II-D allowables.

Group / Regime	Range / Condition	Limit / Criterion	Engineering Notes
S275 / S355 (EN 10025-2 class)	Screening −20 °C to +100 °C ambient	Fy from structural-steel-properties.json	Below −20 °C, confirm toughness / impact requirements for the lift. Above +100 °C, re-rate yield and weld allowables.
ASTM A36 / A572 Gr.50	Screening −20 °C to +100 °C ambient	Fy 36 ksi / 50 ksi class	Use mill cert Fy when thicker plate derates yield. Not a substitute for project fracture-critical review.
Fillet weld E70XX / E80XX	Match electrode to base-metal service	τ_w ≤ 0.30 F_EXX	Both-face fillet assumed along base length L. One-sided welds or intermittent fillets need separate review.

Code Applicability & Safety Boundaries

Field screening only — not a stamped ASME BTH-1 or B30.20 design package.
Sling angle > 60° from vertical is out of scope; use a spreader beam.
Shackle WLL shown is a Grade 80 pin-diameter reference, not a certified rigging selection.
Export / PDF is a duty worksheet — verify final geometry with qualified lift engineering.

4. Step-by-Step Worked Example

Field VerificationShow

Step-by-Step Worked Example: 15 t · 2 Lugs · 30° · S355 Metric

Screen a pad-eye for W_lift = 150 kN, IF = 1.15, two acting lugs, sling angle 30° from vertical, S355 plate t = 25 mm, R_outer = 80 mm, D_hole = 42 mm, D_pin = 38 mm, hole height 150 mm, both-face 12 mm fillet × 160 mm, E70XX (F_EXX = 485 MPa), ASME BTH-1 Category B Nd = 2.0.

W_lift / IF / N:150 kN / 1.15 / 2θ:30° from verticalPlate:S355 · t = 25 mm · R = 80 mmPin / hole:D_pin = 38 mm · D_hole = 42 mmWeld:12 mm fillet × 160 mm both faces · E70XX

Sling tension and shear per lug

P_{t} = W \cdot I F / (N cos θ)

W_design = 150×1.15 = 172.5 kN. P_t = 172.5/(2·cos 30°) ≈ 99.6 kN. P_s = 99.6·sin 30° ≈ 49.8 kN.

Result:P_t ≈ 99.6 kN · P_s ≈ 49.8 kN

Pin-hole bearing vs allowable

σ_{b} = P_{t} / (D_{p in} t) \leq 1.25 F_{y} / N_{d}

σ_b = 99.6×10³/(38×25) ≈ 104.8 MPa. Allowable = 1.25×355/2 = 221.9 MPa → unity ≈ 47%.

Result:σ_b ≈ 104.8 MPa (Pass)

Tear-out and both-face weld

τ_{w} = (P_{t} / A_{w})^{2} + (P_{s} h / S_{w})^{2}

a = 80 − 21 = 59 mm. Tear-out unity ≈ 48%. Both-face A_w and S_w give τ_w ≈ 109.5 MPa vs 0.30×485 = 145.5 MPa → weld unity ≈ 75% (governs). W_safe/lug ≈ 100 kN.

Result:Pass · weld governs · W_safe/lug ≈ 100 kN

Open /15ton-2lugs-30deg-s355-metric for the live default case.

Conclusion: For the default 15 t · 2-lug · 30° · S355 duty, P_t is about 99.6 kN per lug. Bearing and tear-out run near 47–48% unity; both-face fillet weld at ~75% governs. Status is Pass with safe lift capacity per lug near 100 kN under Category B Nd = 2.0.

5. How to screen lifting lug capacity (BTH-1 / AISC)

1
Enter lift duty
Set total lift weight, impact factor, number of acting lugs, and sling angle from vertical (keep θ ≤ 60°).
2
Enter lug geometry and steel
Input plate thickness, outer radius, pin hole and shackle pin diameters, hole height, and select S275/S355/A36/A572-50/SA-516-70.
3
Set base fillet weld
Enter fillet leg size, weld length along the base, and electrode (E70XX or E80XX). The engine assumes both-face fillets.
4
Read W_safe/lug and unities
Hero shows safe lift capacity per lug. Summary chips show bearing, tear-out, and weld unity. Pass means all ≤ 100% and θ ≤ 60°.

6. Frequently Asked Questions & Technical References

Show

Category B uses design factor Nd = 2.0 on yield for the pin-hole bearing and related lug-plate checks in this screen (ASME BTH-1).