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OTHER SIMULATION ISSUES 523

repair, the repair required and the availability of spare that one of the factors affecting the time taken to
parts. Some data have been collected. The elapsed repair equipment is that the repair technician may
time between repairs being needed varies between not carry the necessary spare parts or may not be
one and four weeks and the distribution of repair able to carry out a repair at the clinic because of the
callouts is shown below. So, 50 per cent of callouts lack of the necessary electronic testing equipment to
for a repair happen one week after the last callout; assess exactly what repair is needed. In both cases,
30 per cent happen two weeks after the last callout; the repair technician has to travel back to a central
10 per cent happen three weeks after the last callout; repair depot which adds to the time taken. One
10 per cent happen four weeks after the last callout. option under consideration is equipping the repair
technician with a small van that can carry additional
Time between spare parts and also carry some of the necessary
repairs (weeks) % of repair callouts testing equipment. This would reduce the time taken
to carry out some repairs as shown below:
1 50
2 30 Van option
3 10 Time taken to repair % of repair
4 10 equipment (Days) callouts
1 80
The time taken to repair equipment is shown below.
2 10
40 per cent of repairs take one day to repair, 40 per
3 10
cent take two days and 20 per cent take three days.
The Health Minister has asked for any advice we
Time taken to repair % of repair
can give.
equipment (Days) callouts
Solution
1 40
2 40 Clearly, we could do some simple analysis and cal-
3 20 culate the effect of the Van option on reducing aver-
age repair time. However, this would be quite sim-
The Health Minister has been receiving complaints plistic and might not give a full picture of the effect. It
from community representatives about the fact that is probably more useful to build a simple simulation
local health care at these clinics is often disrupted or model and simulate the effects of introducing the
delayed because medical equipment required is Van option. We have built an Excel model for the
waiting for repair. Initial investigations have revealed problem which shown is in Figure 12.14.
Figure 12.14 Simulation Model for the Repair Problem

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