Light and bright Company has three fairly similar departments making dye additives for the textile industry. Currently there is an on-going discussion concerning the optimum maintenance policy for pump type ZB83, a pump type used in all three departments. Two of the departments, for about 10 years now, use a preventive maintenance policy with an interval of 20 weeks for their 4, and 6 pumps respectively. They are very satisfied with the current PM frequency. The third department, With 10 pumps, uses the same, policy but is not happy with it. Two years ago they skipped a preventive maintenance campaign due to budgetary restrictions and they did not encounter many problems until the 26th week: 1 pump failed in week 26, 2 in week 29, 2 in week 34 and 3 in week 39. They suggest changing the PM frequency from 20 to 30 weeks.

The maintenance manager who coordinates the maintenance activities of the three departments is willing to consider this suggestion. He came led some further information: from the records on 400 pump cyli (while using a PM frequency of 20 weeks). Only 10 cycles were ended because of a pump failure: 1 after 5 weeks, 2 after 10 weeks, 4 after 15 weeks and 3 after 18 weeks. Costs for a PM are 8000 euro. For CM interventions there is an additional cost of 2000 euro in 60% of the cases and of 4000 euro in 40% of the cases.

Is it a good idea to switch from 20 to 30 weeks? Make an estimate of the yearly cost difference.