A core purpose of maintenance is to manage risk. Proper allocation of maintenance’s limited resources depends upon assessing the probability and cost of failure. Let’s look at three key terms that can be confusing when analyzing risk in your facility:
- Probability. There are many ways people determine this, such as the manufacturer’s mean time between failure (MTBF) estimate. But MTBF depends upon certain assumptions. You can bet the MTBF for a motor with 4% voltage imbalance will be much less than the same motor with 1% voltage imbalance. Probability must account for the actual conditions of use.
- Cost. Comparing lost revenue from one type of failure to lost revenue from another type of failure seems logical and straightforward, doesn’t it? If a stamping machine fails and loses $8,000 of revenue that’s not as bad as failure of the drive motor in a robotic welder costing a $20,000 revenue loss. Or is it? What if it’s the light curtain that fails in that stamping press and a worker loses a hand?
- Failure. An extrusion machine is running, so has it failed? What if it has a sensor installation issue that causes erratic control, which results in an 18% scrap rate?