A production model and maintenance planning model for the process industry

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5. Validation of the Model

To demonstrate how the model works, four maintenance scenarios are discussed. The first is a
basic real-life case, with five products scheduled on two identical production lines with the same
speed. The only difference being that production line 1 is old and a inhibits larger probability of a
breakdown, which is reflected in higher expected breakdown costs per period. Demand for the
five products is given in table 3. The planning horizon consists of ten periods of two weeks each .
Round the clock production makes the capacities of both production lines equal to 336 hours per
period. This capacity will be fully utilized in the basic example. The production rates (capacity
divided by processing times) of the five products are given in table 4. Preventive maintenance
costs are 67,500 dollars for each production line. These are one-time costs, including labor costs.
material costs, opportunity costs, and the like. Costs of corrective maintenance are much higher,
and amount to 250,000 dollars for each production line. Expected breakdown costs were
calculated, using the probabilities of a breakdown as listed in table 5. Inventory and backorder
costs are the same for each product: 10 dollars and 100 dollars per ton of product per time period,
respectively. Setup costs are fixed at 1,000 dollars for each product on both lines.

Table 3: Demand Table

Table 4: Production rate

Table 5: Probability of a breakdown

Figure 1 illustrates the relationship between cumulative demand and cumulative capacity,
indicating that the factory loaded almost up to its maximum capacity.

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