Fifty years of reliability and maintenance: A personal view
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Fifty years of reliability and maintenance: A personal view John Crocker Optimized Systems & Solutions, 230 Bristol Business Park, Bristol BS16 1FJ, UK.
Abstract
The reliability of most mechanical and electronic systems has improved dramatically over the past 50 years and yet there are warehouses full of spare parts that will never get used because there is no demand, or because they will reach their use by a date before they are needed or because they will become obsolete. Parts are frequently replaced unnecessarily while others that are much more likely to cause system failures are left untouched. The result is that despite vast sums of money being invested in spares, system availability is still very much a problem. Operations research has the tools that could significantly improve this situation but why are they not being used? OR Insight (2009) 22, 54–63. doi:10.1057/ori.2008.5
Keywords: reliability; maintainability; simulation; renewal process; Poisson process
Introduction The year 1958 saw the start of the space race and the jet age. The USSR (as it was then) had beaten the United States into space by successfully launching two unmanned earth-orbiting satellites in 1957. The United States responded by doing the same in 1958. The first jet airliner, the de Havilland Comet, had been launched in 1949 but had suffered a number of catastrophic failures resulting in the loss of many lives. In 1958, the aircraft was redesigned and launched as the Comet IV. It was followed a month later by the Boeing 707. Britain went on (with the help of France) to build the Concorde (the first supersonic airliner) whereas the United States developed the Boeing 747 ‘Jumbo Jet’ which, alas, proved somewhat more successful. & 2009 Operational Research Society Ltd 0953-5543 OR Insight www.palgrave-journals.com/ori/
Vol. 22, 1, 54–63
Fifty years of reliability and maintenance
In 1959, the BMC Mini took to the streets of the United Kingdom and the first major motorway (the M1) was opened. Although this car sold in large numbers (at least for a UK manufacturer), its price never exceeded its cost so it failed to make any profit for the company. Although buses were expected to last at least 500 000 miles, very few cars made it to 100 000 miles. It was normal for them to have a 6000-mile service interval, to burn copious quantities of oil, require several de-cokes and have their rings and cylinder linings replaced at least once. Fan belts, contact breaker points, condensers, dynamos, batteries, valves, spark plugs, brake shoes, clutch plates were all expected to fail within the first 30–40 000 miles. Motorists were first and foremost mechanics who now and again got to drive their cars. Although there was no speed limit on the ‘open’ road, most cars of that era struggled to exceed 70 mph, which was rather fortunate as most were fitted with cross-ply tyres and drum brakes which meant they tended to take a long time to stop and seldom maintained a straight line while doing so. On the home front, televisions were starting to come into t
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