## Be Prepared For The Toughest Questions

### Practice Problems

A company operates one equipment that is essential in the manufacture of their products

A company operates one equipment that is essential in the manufacture of their products. This machine has been in operation for four years (1000 operating days). In order to plan for next year’s production levels, the availability of the machine must be determined. The company works a single 8-hour shift, 300 days out of one year. Relevant failure and maintenance data collected over this period is:

Failures: Minimal repair with a power law intensity function having a =

0.000125 and b = 1.650 with time measured in operating days

Repairs: Repair time is lognormal with tmed = 2.5 days and s = 0.70

Scheduled maintenance: A preventive maintenance of downtime of one day every five

weeks (30 operating days).

(a) What is the mean system downtime over the first four years?

(b) Based upon both schedule and unscheduled maintenance, determine the expected availability

of the equipment over the coming year (i.e. the next 300 operating days).

(c) If the machine costs \$30,080 to replace and a failure costs \$200, when should the machine be replaced?

Hint

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