| name | crane-design |
| description | Crane design — ASME B30 series, wire rope sizing, hook block, hoist mechanisms, duty class (CMAA spectrum), girder design, wheel loads, stability, dynamic factors, FEM group classification. |
| metadata | {"priority":7,"promptSignals":{"phrases":["crane design","overhead crane","hoist design","ASME B30","wire rope crane","crane girder"],"minScore":3}} |
Crane Design — Complete Skill
Crane Classifications
CMAA Duty Classes (Crane Manufacturers Association of America)
| Class | Usage | Loads | Examples |
|---|
| A | Standby/infrequent | Light, infrequent | Turbine room |
| B | Light | Moderate, 2 hr/day | Assembly, service |
| C | Moderate | 50% NBL, 4 hr/day | Machine shop, paper rolls |
| D | Heavy | 65% NBL, 8 hr/day | Steel service centers |
| E | Severe | 80% NBL, 16 hr/day | Foundry, steel mill |
| F | Continuous severe | 90%+ NBL | Magnet cranes, container ports |
| NBL = net lifting capacity (rated load) | | | |
FEM Classification (European — ISO 4301)
Hoist group: combination of spectrum class (S0–S9) and utilization class (U0–U9)
Mechanism group: M1–M8 (M1 = light, M8 = very heavy)
Structural group: S1–S9
Wire Rope
Rope Selection
Common construction: 6×19 IWRC, 6×37 IWRC (IWRC = independent wire rope core)
Minimum breaking force: F_break from manufacturer tables
Wire rope grade: EIPS (Extra Improved Plow Steel), EEIPS (Extra Extra IPS)
Working load limit (WLL):
WLL = F_break / SF [SF = design factor (safety factor)]
SF per ASME B30.2: SF ≥ 5:1 for all running rope
API/crane: SF = 5 (CMAA Class A–C), SF = 6 (Class D–F)
Rope diameter selection:
D_drum ≥ 18 × d_rope (for Dd/d ratio); CMAA requires ≥ 18:1 to 26:1 depending on class
For CMAA Class E/F: D_drum/d_rope ≥ 26:1
Wire rope life (bending fatigue):
L ∝ (D_drum/d_rope)^1.5 × F_break/WLL [qualitative inverse relationship with reeving ratio]
Sheave Design
Sheave diameter:
D_sheave ≥ 18 × d_rope (same as drum; prefer 26× for severe service)
Fleet angle:
α_max ≤ 1.5° (grooved drum); 2° (smooth drum) — excessive fleet angle causes rope wear
Hook and Hook Block
Hook rating: WLL = rated capacity [tonne or ton]
Forged alloy steel hooks; ASME B30.10 or DIN 15401
Hook proof load test: 1.25 × WLL (ASME); 2.0 × WLL (proof load; European EN 1677)
Hook block design:
Sheave in block; rope reeving determines mechanical advantage (parts of line)
Parts of line n: WLL_hook_block = n × T_rope_max × (η_sheave)^((n-1)/2)
η_sheave = 0.97–0.99 per sheave (ball bearings)
Effective pull on drum:
T_drum = WLL / (n × η^n) [increasing rope tension from load side to drum]
Hoist Mechanism
Hoist motor power:
P_motor = WLL × v_hoist / η_drive [kW; WLL in N; v_hoist in m/s; η_drive = 0.85–0.95]
Gear ratio:
i = n_motor / n_drum = (π × D_drum × n_motor) / (60 × v_hoist)
Drum design:
Length L_drum = n_rope_layers × n_wraps × p_groove [p_groove = rope pitch = 1.1–1.15 × d_rope]
Wall thickness: t_drum = d_rope / 2.5 (rule of thumb); check compressive stress: σ_c = T / (t_drum × L_eff)
Brake torque (hoist):
T_brake ≥ 1.5 × T_load_drum (CMAA Class A–D); ≥ 1.75× (Class E–F)
Separate brake from motor; fail-safe (spring set, electric release)
Overhead Bridge Crane Girder
Load Cases (ASME B30.2)
- Dead load: crane bridge + trolley + hoist weight
- Live load: rated capacity WLL
- Dynamic (impact) factor: per CMAA: Φ = 1 + 0.5v_hoist [v in m/s; max Φ = 1.3 for Class A–C; 1.5 for E–F]
Or Φ = 1 + 0.1 × h_lift [h_lift in meters; per some standards]
- Inertial forces (acceleration): horizontal thrust = 20% of WLL (CMAA default)
- Skewing force: for long-span cranes; lateral forces from travel
Design load for girder:
P_design = (WLL + trolley_weight) × Φ
Wheel loads:
R_1 = P_design × (L - a) / L + Dead_load/2 [a = distance from left end to trolley; L = span]
R_2 = P_design × a / L + Dead_load/2
Girder Stress Limits (AISC LRFD or ASD for crane)
Bending stress:
f_b = M_max / S ≤ F_b [F_b = 0.66 F_y for compact AISC ASD]
Deflection limit:
δ_max ≤ L/600 (CMAA Class A–C); L/888 (D–F) under rated load
δ = P_design × a²(3L-4a) / (48EI) [for mid-span load; adjust for trolley position]
Fatigue (AISC fatigue categories):
Runway girder top flange: Category C or D; S_r ≤ allowable fatigue stress range
Number of load cycles: N = duty class × lifetime
Runway Rail
Recommended: ASCE rail for wheel load W [tons]:
W ≤ 5 tons → 25 lb/yd; W = 5–15 → 40 lb/yd; W = 15–30 → 60 lb/yd; W > 30 → 85–104 lb/yd
Bridge Travel and Stability
Bridge travel motor power:
P_travel = (F_rolling + F_slope + F_acceleration) × v_travel
F_rolling = μ_r × G_total [μ_r = 0.01–0.02 for crane wheels on rail]
Anti-tipping check (mobile crane):
Stability ratio = M_stabilizing / M_overturning ≥ 1.15 (loaded); ≥ 1.25 (unloaded)
Buffer stops:
Energy: E_buffer = 0.5 × M_bridge × v_impact² × (1 - e²) [e = coefficient of restitution; 0 for rigid stop]
Buffer capacity ≥ E_buffer
Lifting Accessories
Slings:
Wire rope sling WLL = rope WLL × sling efficiency factor (angle factor)
Angle factor: 90° = 1.0; 60° = 0.866; 45° = 0.707; 30° = 0.5
ASME B30.9 sling rating
Chain slings:
Grade 80 alloy chain; WLL × angle factor
ASME B30.9; OSHA 1910.184
Standards
| Standard | Scope |
|---|
| ASME B30.2 | Overhead and gantry cranes |
| ASME B30.10 | Hooks |
| ASME B30.9 | Slings |
| CMAA Spec 70 | Top-running bridge cranes |
| CMAA Spec 74 | Top-running single girder |
| EN 13001 | Crane safety — general principles |
| ISO 4301 | Classification for crane mechanisms |
| OSHA 1910.179 | Overhead and gantry cranes (US) |
Output
Provide: crane type and CMAA class, rated capacity WLL [tonnes], span L [m], hoist speed [m/min], wire rope size d [mm] and breaking force [kN] with SF, drum diameter D [mm] and D/d ratio, number of parts of line n, hoist motor power [kW], dynamic factor Φ, maximum wheel load [kN], girder size (W-shape or box), bending stress [MPa] vs. allowable, girder deflection [mm] vs. L/600 limit, runway rail size [lb/yd], brake torque [N·m] vs. minimum required, and applicable standard (ASME B30.2, CMAA 70).
