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The assembly generating the lifting movement – motor, gearbox, brake and load-bearing medium. In crane engineering the hoist is classified into mechanism groups deriving expected service life from load spectrum and running time. Too low a classification is the commonest reason a device shows unexpected wear after two years of three-shift operation.
The hoisting mechanism is the assembly of a hoist that raises, lowers and holds the load. It comprises the motor, the gearbox, the brake, the rope drum or chain wheel and the rope or chain itself. Then there are the devices that limit operation: the hoist limiter for the end positions and the overload protection.
Two hoists of equal capacity can be built very differently – depending on how often and how hard they are meant to work. The mechanism group expresses this duty. It results from two quantities: the average daily running time and the load spectrum, that is, whether the hoist mostly lifts light loads or regularly lifts its full capacity.
Two corresponding designation systems are in use: the groups of FEM 9.511 and the M classes of ISO 4301-1. The higher the group, the greater the running time or load spectrum the hoist is rated for.
The mechanism group implies a theoretical service life. A hoist loaded more lightly than assumed uses it up more slowly; one working close to capacity in three-shift operation correspondingly faster.
The portion used is determined from operating hours and the actual load spectrum and recorded at the periodic inspection; the method is described in FEM 9.755. Once the theoretical service life is reached, the hoist may only continue in service after a general overhaul. In English the concept is known as the safe working period (S.W.P.).
The brake of a power-driven hoist is built to close without energy: if the power fails, it holds the load. In addition, the EU Machinery Directive requires machinery with a working load of 1,000 kilograms or more, or an overturning moment of 40,000 newton metres or more, to have devices that warn of overloading and prevent dangerous movements.
Selection is often by capacity and price alone. A hoist in too low a mechanism group carries the load without trouble from day one – and after a short time in multi-shift operation shows wear on brake, gearbox and rope or chain. The right question is therefore not only “how heavy” but also “how often, for how long and at what share of the capacity”.
What Entracon offers here is on the matching page.
See what we offer| Group to FEM 9.511 | Class to ISO 4301-1 |
|---|---|
| 1Bm | M3 |
| 1Am | M4 |
| 2m | M5 |
| 3m | M6 |
| 4m | M7 |
It describes how the lifted loads are distributed over the running time. A light spectrum means mostly small loads and rarely the full capacity. A heavy spectrum means regular loads close to capacity.
From the operating hours and the actual load spectrum. An hours counter or a load spectrum recorder supplies reliable values; without them the figures are estimated and a margin is added. The result belongs in the inspection records.
A general overhaul is then due, in which the manufacturer or a body authorised by it inspects and replaces the specified components. After that a new period of use begins.
No. The mechanism group says nothing about a higher capacity but about service life under a given duty. The capacity on the rating plate applies unchanged.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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