To avoid accidents with the crane due to wear and age, it is essential to always ensure that the hoist operates within a safe working period.

The hoist operates within a safe operating period if the actual hours of use (S) are fewer than the number of hours representing the theoretical service life (D).

The theoretical service life (D) is determined and specified by ABUS according to the generally accepted engineering standards. The theoretical service life is given in full-load hours. A full-load hour is defined as the hoist having operated at its maximum load capacity for one hour.

The actual hours of use (S) of the hoist must be determined by the end user. The value must be determined based on the operating hours, the load spectrum and additional factors.

In order to also take into account the operating phases of the hoist in which the hoist was not operating at maximum load capacity, but instead lifted lesser loads, there are four different load spectrums (Km). The load spectrum (Km) is a mathematical factor. It specifies how great a load is actually placed on the hoist during operation.

There are four load spectrums

─     Light (Km = 0.5)

─     Medium (Km = 0.5 to 0.63)

─     Heavy (Km = 0.63 to 0.8)

─     Very heavy (Km = 0.8 to 1.0)

In the light load spectrum, for example, the hoist often runs with an empty load hook and transports light loads (in relation to its maximum load capacity). In the very heavy load spectrum, for example, the hoist seldom runs with an empty load hook and nearly always transports loads at its maximum load capacity.

The load spectrum thus specifies the degree to which the hoist is subjected to its maximum load capacity or only to lesser operating demands.

Examples:

Example of the “light” load spectrum (Km = 0.5)

Example of the “medium” load spectrum (Km = 0.5 to 0.63)

Example of the “heavy” load spectrum (Km = 0.63 to 0.8)

Example of the  “very heavy” load spectrum (Km = 0.8 to 1.0)