Maddox Smith Staff asked 4 years ago

5 Questions

Q 1 The propulsion system of a twin-screw cruise ship consists of four high-speed diesel engines. Each propeller shaft is driven by a pair of engines through a gearbox.  During the course of designing the ship, two different proposals are considered for the operation of the pairs of diesels in the propulsion system. The first configuration involves making each pair of diesel engines standby parallel systems. The active engine of each pair has a failure rate of 7000 per million hours. The standby engine is assumed not to fail while idle. Switching between engines is imperfect, with a probability of switching failure of 2%. A gearbox in this configuration has a failure rate of 280 per million hours. There are no common cause failure modes. The second configuration is to operate a pair of diesels in an active parallel configuration. The failure rate of each engine is 5000 per million hours, and is unaffected by how many engines are working. Common cause failures are modelled with a beta-factor of 10%. A gearbox in this configuration has a failure rate of 200 per million hours. Irrespective of the configuration, the ship will sail safely with just one operational diesel engine. A cruise lasts five days. Ignoring the possibility of repairing a failed engine before another engine fails, determine the probability of complete propulsion system failure before the end of the cruise for each configuration. Hence decide which of the two design proposals is the most reliable                       Question 4        Q 1       Q 2         Q 7  next 2 pages