City Guilds Model Questions Vol1 2018 Engineering Question 44
Practice objective / multiple choice question 44 from the 2018 City Guilds Model Questions Vol1 Engineering examination.
A machine contains two critical components, X and Y, whose times to failure are exponentially distributed with mean times to failure of 200 h and 300 h respectively. Preventive maintenance replaces component X every \(T_X\) hours and component Y every \(T_Y\) hours, where both \(T_X\) and \(T_Y\) are integer multiples of 50 h. A failure causes an immediate shutdown lasting 4 h, while a preventive replacement causes a shutdown of 2 h. The overall system efficiency is 85%, meaning only 85% of the scheduled power is available after maintenance losses. Over a 1000‑hour operating period, determine the pair \((T_X, T_Y)\) that minimises the expected total downtime and give that minimum expected downtime (in hours).
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About This Question
This is City Guilds Model Questions Vol1 2018 Engineering Question 44. It is one of the objective questions from the 2018 City Guilds Model Questions Vol1 Engineering examination.
Difficulty level: Hard .
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