a) Define reliability, availability and maintainability. Outline the relationship of availability to reliability and maintainability.
b) Define the hazard rate, the formula and give a reason for its use. With the aid of a sketch, show and explain how the hazard rate function of a typical mechanical system varies with time and outline its three different life phases.
c) Ten identical pumps were put on test for 50 days, and their failure times (hours) were observed to be:
10, 16, 26, 33, 34, 36, 39, 42, 44, 48.
i. Calculate the MTTF;
ii. Estimate the reliability of the pump at 30 days;
iii. Re-calculate the reliability of the system at 30 days, if another identical pump is placed in parallel to the existing pump in ii).
d) The method of moving averages is often used for trend analysis. Explain the purpose of using the method of moving averages. Also, explain how the method can be used to identify a trend for number of failures per month of a component. Comment on the effect of different averaging periods on the trend.
