Home Health Case Studies in Maintenance and Reliability: A Wealth of Best Practices
The superior man, when resting in safety, does not forget that danger may come. When in a state of security he does not forget the possibility of ruin. When all is orderly, he does not forget that disorder may come.
Thus his person is not endangered, and his States and all their clans are preserved.
..... Confucious, 551BC to 479BC.
Author: V. Narayan
Location: 2.1.4 A Large Petroleum Refinery
On taking up my position as area engineer, one of the things I found at this site was quite intriguing. We were doing 'function-testing' as the sole method of checking whether large rotating machinery tripped on overspeed (or other trip signals).
When there is an unsafe condition such as excessive axial displacement, the detector sends signals to the logic device (black box). This processes the signals and initiates corrective action by the actuator. Function tests do not exercise the actuators. Therefore, they (the final element as instrument engineers call it) may give a false sense of security—we cannot verify whether the valve or other final element would actually move (open or shut) as required. On the other hand, they do help to avoid the production downtime caused by full checking of the complete trip systems"
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