October 2019

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Reliability: Viewing issues out of context may be a waste of time

An alternative to the above title would be “Test your rotating equipment engineers’ IQ.”

Bloch, Heinz P., Hydrocarbon Processing Staff

An alternative to the above title would be “Test your rotating equipment engineers’ IQ.” Depending on context and where the apostrophe is placed, the invitation to “test” is extended to you personally, or to your manager. Without taking the time to examine and fully understand context, claims and statements quickly become legends and anecdotes that entertain, at best, and cause serious damage, at worst. Six recent examples come to mind; they will be of interest to readers who wish to stay informed.

1. “Our large refinery (‘OLR’) cannot justify oil mist on a plant-wide basis.”

Answer: Yes, no, maybe.

Explanation: The engineers at OLR apparently do not realize that best-of-class competitors use oil mist not only on pumps, but also on electric motor drivers. It would indeed take that refinery a fair amount of money to implement oil mist on a plant-wide basis. However, at present, OLR must periodically regrease its electric motor bearings. Even if done right, re-greasing will consume maintenance dollars. If cost justification calculations do not include facts and true overall costs, then the calculations are meaningless.

2. “It’s an insidious myth to claim that a reliable plant is a safe plant.”

Answer: Yes, no, maybe.

Explanation: Perhaps the quote comes from someone whose primary interest is in selling operator training, systems integration and similar services. Safe operation is built into a reliable plant. Check it out, and steer clear of companies in the business of marketing consultant-conceived generalities. Hire those that can point to quantifiable achievements and can demonstrate how (or if) they have added value to an enterprise.

3. “Shielded bearings cannot be regreased.”

Answer: Yes, no, maybe.

Explanation: These bearings have a small, circumferential gap between the stationary shield and the bearing’s rotating inner ring. The original design intent is to provide bearing housings with a grease cavity (reservoir) adjacent to the bearing and to let small amounts of oil leave the grease and “bleed” into the bearing. Trying to force grease past the gap and into such bearings has been known to deflect the shield and ruin the bearing. Done right, shielded bearings can be regreased.

4. “A recent reference text on incident investigations speaks of pump problems leading to the Bhopal disaster in December 1984. I do not believe that pumps were involved.”

Answer: Yes, no, maybe.

Explanation: Failure to consider human factors in the context of mechanical reliability issues leads to “believing” theories about what may have caused a system malfunction instead of digging deeper for credible, fact-based answers. The Bhopal disaster is just one of many examples that demonstrate how early speculation into various theories can hamper the intelligent pursuit of needed information. Uncovering required information puts controversial and often accusatory facts into their proper context.

Fig. 1. A well-proven dual mechanical seal upgrade that would have complied with calls to discontinue use of failure-prone single mechanical seals in circulator pumps at the Bhopal plant. Source: AESSEAL Inc.
Fig. 1. A well-proven dual mechanical seal upgrade that would have complied with calls to discontinue use of failure-prone single mechanical seals in circulator pumps at the Bhopal plant. Source: AESSEAL Inc.

Therefore, a true reliability professional is careful not to put faith in incomplete and inconclusive theories. True experts are unbiased. They accept explanations backed by a trustworthy incident investigation process. Had this attitude prevailed in the Bhopal factory, perhaps certain earlier requests to upgrade to dual mechanical seals (similar to Fig. 1) would have been heeded, thereby solving a serious pump issue.

A thoroughly well-researched text1 contains facts on the matter and cites authoritative references found in the more recent Indian High Court proceedings. Documenting how and why we should fully absorb the incident today, the book harmonizes with experiences common to professionals that have struggled with process and mechanical reliability issues in a production environment. To a failure investigator looking at the whole picture, pump seal issues and how they were handled had immense consequences in the Bhopal incident.

5. “We do not think automatic unloaders are cost justified on large reciprocating compressor cylinders. Our operators will manually unload cylinders, if needed.”

Answer: Yes, no, maybe.

Explanation: If a power outage occurs, and a crankpin or crosshead pin obstructs an oil supply hole while pressurized gas keeps pushing on the piston, the babbitted bearing will overheat. Expensive downtime and repair costs have resulted and are known to reliability engineers;2 although, as a rule, company lawyers will rarely allow outsiders to learn the true root causes and chains of events.

6. “Pump repairs are not a high priority for us. We have standby spares for all services at our plant.”

Fig. 2. After three identical pumps experienced 23 seal failures within  12 mos, pump fire statistics (one fire per 1,000 failures) caught up with a refinery in New Mexico. Source: US Chemical Safety Board.
Fig. 2. After three identical pumps experienced 23 seal failures within 12 mos, pump fire statistics (one fire per 1,000 failures) caught up with a refinery in New Mexico. Source: US Chemical Safety Board.

Answer: Yes, of course spares are in place. However, each failure event or repair intervention increases the probability of a pump-related fire (statistically, one fire per 1,000 failure events); moreover, each repair costs money (Fig. 2). Therefore, failure avoidance through upgrading (meaning the elimination of weak links, and consistently enforcing safe operating procedures) is among the prime objectives of best-of-class companies. Incidentally, it also reinforces our firm belief that a reliable plant is a safe plant. Arguing otherwise is an unproductive exercise in semantics and has little to do with reliability engineering.

Remember: People may be the weakest link if they disregard proper operating procedures. Reliability improvement efforts must be supported by sound management and by maintaining focus. Failure avoidance strategies backed by informed managers will provide rapid payback. Experienced managers will not let word games divert attention away from true safety and reliability. Regardless of job function, it is important to steer clear of hearsay. There is never a sensible substitute for examining asset events in their proper context. HP

Literature cited

  1. Bloch, K. P., Rethinking Bhopal, Elsevier, Amsterdam, the Netherlands, Oxford, the UK and Cambridge, Massachusetts, 2016.
  2. Bloch, H. P., Petrochemical Machinery Insights, Elsevier Publishing, Oxford, UK and Cambridge, Massachusetts, 2016.

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