FEM & ISO crane selection criteria, hoist duty groups, load spectrum and Safe Working Period — the engineering reference Wimac uses to specify every project.
Choosing the correct crane configuration starts with a structured evaluation of duty class, load spectrum and operating profile. The guide below summarises the FEM & ISO criteria used by Wimac engineering to specify every project.
As per the FEM / EN standard, hoist usage is categorised into duty groups: 1 Bm (M3), 1 Am (M4), 2 m (M5), 3 m (M6) and 4 m (M7). 1 Bm (M3) represents the lightest usage, while 4 m (M7) indicates the heaviest. When no specific duty requirement is provided, the commonly referenced class is FEM 2 m / ISO M5.
The crane and hoist duty groups are determined separately and can be different. Hoist duty groups are calculated from three factors: load spectrum Q, average operating time per day (t), and other working-condition factors.
| Operation Mode | Description | 1 Am | 2 m | 3 m |
|---|---|---|---|---|
| Light | Mechanisms that typically handle very light loads and reach maximum loads only in rare or exceptional situations. | 2–4 | 4–8 | 8–16 |
| Medium | Mechanisms that operate with moderate loads throughout the working day. | 1–2 | 2–4 | 4–8 |
| Heavy | Mechanisms that frequently handle loads close to the maximum rated capacity. | 0.5–1 | 1–2 | 2–4 |
SWP is calculated according to the actual use of the hoist in hours. The theoretical service life is based on a 10-year expected SWP for a new hoist and depends on the Hoist Duty Group.
| SWP — Theoretical Service Life (D) hours | ||
|---|---|---|
| Hoist Group | Load Spectrum | M3 (1B m) · M4 (1 Am) · M5 (2 m) · M6 (3 m) |
| Q1 | Light (kp = 0.125) | 3200 h · t ≤ 2 |
| Q2 | Medium (kp = 0.25) | 1600 h · t ≤ 1 |
| Q3 | Heavy (kp = 0.5) | 800 h · t ≤ 0.5 |
