CRL Reliability Engineering 2

Question 1

Two components with reliabilities of 0.90 and 0.95 are arranged in series. What is the system reliability?

Accepted Answer

0.855

Answer

Series reliability is the product of component reliabilities: 0.90 × 0.95 = 0.855.

Question 2

Two identical pumps, each with reliability 0.80, run in active parallel redundancy. What is the system reliability?

Accepted Answer

0.96

Answer

Parallel reliability = 1 − (1 − 0.80)² = 1 − 0.04 = 0.96.

Question 3

A Weibull analysis returns a shape parameter (beta) of 0.7. What failure behavior does this indicate?

Accepted Answer

Infant mortality with a decreasing failure rate

Answer

A beta below 1 means the failure rate decreases over time, which points to early-life or infant mortality failures.

Question 4

An asset runs with an MTBF of 500 hours and an MTTR of 20 hours. What is its inherent availability?

Accepted Answer

96.2%

Answer

Inherent availability = MTBF / (MTBF + MTTR) = 500 / 520 ≈ 96.2%.

Question 5

In a Weibull distribution, what does the characteristic life (eta) represent?

Accepted Answer

The time by which about 63.2% of the population has failed

Answer

Eta is the time at which about 63.2% of units are expected to have failed, whatever the value of beta.

CRL - Certified Reliability Leader Practice Test