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I hope readers now have some understanding of how machinery professionals approach reliability reviews. We have discussed the three facets of machinery reliability assessments: A review of machinery criticality, equipment history, and safeguards. These three aspects of a machine are required to obtain a snapshot of the current state of reliability. After determining the criticality of a machine, we must evaluate the cause-and-effect relationships between adverse machine conditions and the various failure modes. We need to ask ourselves: Are these cause-and-effect relationships understood and repeatable? If they are, then we can begin to design proper safeguards to avoid future failures as a way of improving availability. For example, if we know that a low pump flow causes high vibration due to internal recirculation, which in turn causes a mechanical seal failure, then we may need to consider an automatic flow spillback valve to preclude low flow conditions. Keep in mind that every safeguard must be cost justified, i.e., the cost of each safeguard must return value in the form of reduced risk associated with the improvement.

Reliable operation requires: 1) proper physical safeguards, such as surge control, temperatures and vibration monitors, load monitors, speed sensors, etc., to prevent and detect unwanted operating conditions, 2) well-written operating procedures, and 3) judicious design improvements. We must be ever vigilant if we wish to keep our rotating machinery out of harm’s way and operating reliably by avoiding undesirable operating conditions at all stages of a machine’s lifetime. Before writing compressor operating and monitoring procedures, you need to clearly understand your machinery’s operating limits. If in doubt, talk to the original equipment manufacturer about any concerns you may have. Always try to be conservative when setting operating limits. If you faithfully protect your process machinery with effective safeguards, you will be rewarded with many years of safe and reliable service.