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Normalization of deviance can kill

06.01.2014  |  Bloch, H. P.,  Hydrocarbon Processing Staff, 

Keywords: [risk plan] [best practices] [maintenance]

On January 28, 1986, the space shuttle Challenger (mission STS-51-L) broke apart just 73 seconds after launch. The seven-member crew of the shuttle lived until 3 minutes and 58 seconds after launch, which is when the crew compartment struck the Atlantic Ocean at over 200 mph. The origins of the Challenger disaster are traceable to issues ranging from deep-seated human failings by top decision-makers to poor and mishandled design decisions involving O-rings.

Failure scenario

An O-ring failure had been anticipated by more than one competent individual well ahead of the launch. With honesty and courage, the Thiokol engineers had issued early warnings concerning the O-ring application at extreme cold temperatures. Unfortunately for the Challenger crew, the minus-side of the figurative ledger is populated by the usual suspects—the folks who prefer to drift with the prevailing currents. Because of the disaster’s complexity and ramifications, well over 100,000 pages of reports and findings have been generated. Most documents are in the public domain, and a few knowledgeable people have issued syntheses of the vast amount of material.

Although many well-focused summaries apply to the process industries, one has a special impact. It was prepared by Richard “Mike” Mullane, a former astronaut, left, in Fig. 1. Mr. Mullane had flown on three space shuttle missions and is uniquely qualified to convey pertinent facts regarding this program. In 2013, the author had two opportunities to hear Mr. Mullane speak at ExxonMobil’s (EM’s) maintenance productivity conferences. EM recognized that the lessons from the Challenger disaster have great value to equipment users in all modern industries.

  Fig. 1. Mike Mullane (left)
  with Heinz Bloch at a 
  recent EM maintenance
  productivity conference.

Mr. Mullane spoke about original plans to have 26 space shuttle ascents per year from different launch sites. He related how these underfunded plans were so unrealistic as to rightly be called an “economic lie.” Mr. Mullane examined why bad things happen to teams with stellar credentials and seemingly flawless success histories. His answers are found in practices that are often observed in the hydrocarbon processing industry (HPI), and are commonly called normalization of deviance.1 Unfortunately, normalization of deviance leads to predictable surprises and incompetent engineering management, all adding to the risk of a disaster.

Parallel conditions

The similarities between NASA and the HPI are uncanny. Some reliability engineers in the HPI find themselves getting away with deviation “a,” and they know that they have also gotten away with deviations “b,” “c” and “d.” When allowing deviation “e” to be added to project, the engineers are surprised that things blow up when the resulting safety margins drop below zero. These engineers allow schedule pressures to dictate the pace of work and reduce the time left for reviewing details, thus leaving no time left for meaningful inspections or verifications. These staffers allow procurement of lube oil, gaskets, bearings or mechanical seals from the lowest bidder. They tolerate an alliance partner whose overall quality is inferior. They summarily reject higher initial-cost bidders instead of determining the lifecycle costs. They either do not know, or simply forget to explain to management that purchasing—at premium cost—from vendors with application engineering expertise is the path to best practices.


One option involves reliability professionals closely mapping out career paths that require more nurturing and grooming of knowledge. True professionals must develop an aversion to repeat failures of equipment. More importantly, they must offer researched facts instead of quick opinions. As Mr. Mullane explained, it is often dangerous to structure an initially favorable outcome into false feedback. The initial absence of a problem does not mean that there will be no problems later.2 Consider the automobile industry and its history of vehicle recalls. How many times is “getting away with it” not the equivalent of “always getting away with it”?


The prescription for soundly managed reliability engineering can be lengthy, and it deserves more detailed explanations. Here are a few of Mr. Mullane’s findings to consider:

  • Recognize the vulnerability. Safety and quality rank well above schedules.
  • Practice situational awareness. Understand that, while a work environment will surely change over the long run, it can also change unexpectedly in the short term.
  • Interpret an anomalous result. Do not be predisposed as to its cause.
  • Avoid shortcuts. Do not let an aggressive “can do” culture maneuver support shortcuts.
  • Review worst practices. Always stick to best practices without compromise.
  • Speak up. If you see something amiss, speak up and say something.
  • Review best practices. Periodically reset best practices to meet conditions.

Convergence of bad decisions

Yes, the Challenger disaster had much to do with an unsuitable joint design. But joints that survived were the real anomaly here. While the unusually cold launch temperature on January 1986 aggravated the design flaw, it was certainly not the only reason for all of the flaws. Mr. Mullane made that point masterfully. He managed to explain what stands in the way of achieving true reliability. HP


1 Vaughan, D., Challenger Disaster, University of Chicago Press, Chicago, Illinois, 1996.
2 Mullane, R. M., Riding Rockets, Scribner Publishers, New York, 2007.

The author
HEINZ P. BLOCH resides in Westminster, Colorado. His professional career began in 1962 and included long-term assignments as Exxon Chemical’s regional machinery specialist for the US. He has authored over 580 publications, among them 18 comprehensive books on practical machinery management, failure analysis, failure avoidance, compressors, steam turbines, pumps, oil mist lubrication and practical lubrication for industry. Mr. Bloch holds BS and MS degrees in mechanical engineering. He is an ASME Life Fellow and a registered professional engineer in New Jersey and Texas. 

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