1. The failure rate for a high-speed fan is given by λ(t) =
(2.3 x 10-4+ 3.2 x 10-6 t) / hr,
(2.3 x 10-4+ 3.2 x 10-6 t) / hr,
where t is in hours of operation. The required design-life
reliability is 0.96.
reliability is 0.96.
(a) How many hours of operation should the design life
be?
be?
(b) If, by preventive maintenance, the wear contribution to
the failure rate can be eliminated, to how many hours can the
design life be extended?
the failure rate can be eliminated, to how many hours can the
design life be extended?
(c) By placing the fan in a controlled environment, we can
reduce the contribution of random failure to λ(t) by a factor of
two. Then, without preventive maintenance, to how many hours may
the design life be extended?
reduce the contribution of random failure to λ(t) by a factor of
two. Then, without preventive maintenance, to how many hours may
the design life be extended?
(d) What is the extended design life with both preventive
maintenance and controlled environment?
maintenance and controlled environment?
