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Q11 A system has MTBF of 200 hrs. Calculate the 100 hr. reliability of a system

ID: 1717347 • Letter: Q

Question

Q11

A system has MTBF of 200 hrs. Calculate the 100 hr. reliability of a system in which one such unit is operative and two identical units are standing by.

Two components each with an MTBF of 1000 hours are connected in (1) active (2) standby redundancy. Determine the overall system MTBF.

The failure rate of a device is constant equal to 0.06x10-3 per hr. How many standby devices are required to achieve a reliability of more than 0.985 for an operating period of 10,000 hrs? What is the MTTF of the resulting system?

Explanation / Answer

Reliablity = e^-T/M

T = time = 100 hr

M = MTBF = 200 hrs

R = e^-100 /200

Reliabilty = 2.21

c = 0.06 x 10 ^-3 /hr

Total reliabilty R = 0.985

time T = 10000 hrs

R = e ^-CT

0.985 x n = e^-0.06 x 10^-3 x 10000

n = no of stand by devices = 3

MTTF= 1 /C

MTTF = 1/ 0.06 x 10^-3

= 16666.66 hrs

overall system of MTBF = 1000/2

= 500 hrs