Until World War II, industry was not very highly mechanised. Most of the equipment was simple and over-designed. Failure consequences were not vital and had a neglected effect. Therefore, industrial equipment was operated until it failed, at which point it was either repaired or replaced ‘‘fix it when it breaks’’. Maintenance was considered as a production task and a necessary evil. The first maintenance approach could be described as reactive maintenance where no action is taken to prevent failures or to detect the onset of failure. The maintenance related costs are usually high, but this approach could be considered cost-effective in certain cases