Category Archives: Theory and definitions
Conditional failure probability, reliability, and failure rate
What is the relationship between the conditional failure probability H(t), the reliability R(t), the density function f(t), and the failure rate h(t)? In the article Conditional probability of failure we showed that the conditional failure probability H(t) is: X is the failure … Continue reading
Conditional probability of failure
The most powerful information sought by all maintenance engineers and managers boils down to the conditional failure probability. It is the probability of an item failing in an upcoming period of interest knowing that it is currently in an unfailed state. If you … Continue reading
Posted in Reliability Analysis, Theory and definitions
Tagged Conditional failure probability
1 Comment
MTTF is the area under the reliability curve
The reliability curve, also known as the survival graph eventually approaches 0 as time goes to infinity. How do we show that the area below the reliability curve is equal to the mean time to failure (MTTF) or average life … Continue reading
Random failure and the MTTF
Nowlan and Heap said that the (conditional) probability of occurrence of most failure modes is constant throughout the life of a component. They described this behavior as being that of “random” failure. What is the Mean Time to Failure (MTTF) of a randomly … Continue reading
Expected failure time for an item whose maintenance policy is time-based
Let Tc be the time of a cycle, tp the preventive maintenance time interval, and T the failure time. The expected life cycle Tc will be the planned maintenance time tp multiplied by the probability that planned maintenance does occur, plus the … Continue reading
Posted in Theory and definitions
Leave a comment