In the analysis of repairable equipment, one may need to make the assumption of constant failure rate. In my opinion, anytime one wants to make the assumption of constant failure rate, it should be validated. [Read more…]
Archives for January 2013
Statistical Confidence
An error that I see on occasion is the use of statistical confidence with a goal or target value. For example, we want 95% reliability at five years with 90% confidence. What does that mean? [Read more…]
MTBF and preventative maintenance
I find the world of maintenance a very odd place to find MTBF. While it is possible, that a set of equipment or a machine may actually have a constant failure rate it is the exception rather than all that common. Assuming a constant failure rate doesn’t make it so. [Read more…]
Hypothesis Test Sample Size
Hypothesis testing permits us to compare two groups of items and determine if there is a significant difference or not. There are many types of hypothesis tests depending on the specific question, type of data, and what is or is not known when designing the test. [Read more…]
Reliability Centered Maintenance
The document by Nowlan and Heap
Part of keeping equipment operational is affecting repairs appropriately. Sometimes it makes sense to replace an element of some equipment before it fails, i.e. automobile tires as the tread wears. Sometimes is doesn’t make sense to repair a functioning unit as the result would be a system that is less reliable then before. [Read more…]
Emerging Technology Reliability Considerations
As we continue to find and improve ways to master our environment, accomplish tasks, communicate, move, heal, etc. we continue to discover new materials, processes, and products. Emerging technologies often promise
- lower costs
- new functions
- lighter weight
- easier to use
They also may last longer.
As a minimum, they should last long as current solutions or longer or provide another compelling reason to use the new technology. [Read more…]