Wrench time

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Wrench time ( AE : wrench time  = "wrench time") is a key figure commonly used in America for measuring management performance in (reactive) maintenance . It is assumed that it is the task of maintenance management to ensure that maintenance employees spend as high a percentage of their time on site as possible working on systems (wrench time). It is tacitly assumed that only necessary work and that are carried out in normal performance . This represents a departure from the earlier idea that it is actually a good sign when maintenance staff “sit around” without doing anything because the systems are then running and producing.

The definition is still controversial. There is broad agreement that only the time of the closer on-site time of the maintenance engineer (main and secondary activities according to the REFA definition of the on-site activities) should form the counter. If in doubt, a time that is not directly used for maintenance of the system should not be included. Every preparation, set-up , fetching material, fault finding, filling out documents etc. can and should be avoided or at least reduced by the management and therefore remains outside the key figure.

The information on the denominator has been more controversial so far. Planned attendance times of employees are almost always used. There is a tendency here to use as long a time as possible, i.e. also to leave further training, illness and vacation times, and even the public holidays, in the same period.

This leads to small wrench times and thus suggests high potential for rationalization.

The literature therefore also classifies around 30% wrench time as an average and around 70% as world class.

Too wide a reference time in the denominator, however, contradicts the measurement concerns of the key figure. Maintenance managers have no influence on the number and location of public holidays, nor on the results of collective bargaining and company agreements on working hours. The key figure should therefore be kept free from such influences. Subsequently, the denominator should sensibly contain the actual working hours of the period, best determined by the HR department. The 1,770 hours per year determined by the Institute for Work and Technology (IAT) for German full-time employment relationships could be used as an approximation .

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