JD Neuhaus said, according to ISO 4301/1 and FEM 9.511, series lifting equipment is classified and dimensioned into groups depending on the operating conditions. The group hoists are classified in is determined by the class of operating time and the load spectrum. The class of operating time indicates the average daily operating time. The load spectrum indicates to what extent a hoist or its parts are subject to maximum stress or to smaller loads only.

Four load spectra are distinguished: L1 (light), L2 (medium), L3 (heavy) and L4 (very heavy). By applying the class of operating times and the load spectra, the hoists are classified into eight groups. This results in the theoretical operating time.

By comparing the theoretical operating time with the actual operating time, the used rate of the theoretical operating time can be calculated. When the theoretical operating time has been reached, the hoists must be put out of operation or a general overhaul must be performed according to manufacturers requirements so that the hoists can be operated further, JD Neuhaus said.

The JD Neuhaus online calculator, available at www.jdn.de, is capable of calculating the remaining theoretical use of its air hoists. JD Neuhaus hoists built before 1982 are not covered by the tool.