City Guilds Model Questions Vol1 2021 Engineering Question 33
Practice objective / multiple choice question 33 from the 2021 City Guilds Model Questions Vol1 Engineering examination.
A machine experiences an exponential failure rate of \(\lambda = 0.02\ \text{failures h}^{-1}\) when operating normally. After a preventive maintenance action the failure rate drops to \(\lambda_p = 0.005\ \text{h}^{-1}\). Each preventive maintenance takes 1 h of downtime and costs \(\text{₦}800\). A failure incurs a repair cost of \(\text{₦}5000\) and an additional 2 h of downtime (lost production valued at \(\text{₦}1000\) per hour). Determine the preventive‑maintenance interval \(t\) (in hours) that minimises the expected cost per hour of operation.
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About This Question
This is City Guilds Model Questions Vol1 2021 Engineering Question 33. It is one of the objective questions from the 2021 City Guilds Model Questions Vol1 Engineering examination.
Difficulty level: Hard .
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