Front-line operations department employees in facilities handling hazardous materials are increasingly involved in making many decisions during the course of their workday, the outcome of which could affect the risk of accidental exposure to themselves and others. We as managers of risk should ask ourselves if those decisions are based on sound scientific principles and application of rational logic. Or are the employees unknowingly exposing themselves to a variety of high-risk activities, when lower risk alternatives are available for the asking?

What Risk? A Scenario to Consider

Take the case of an operator with 10 years of plant experience whose responsibilities included logging a fractionation tower’s locally installed pressure gauge reading. The tower produces a light hydrocarbon overhead product, a highly volatile flammable mixture at moderate pressure, and has had no history of problems. The gauge is located at the safety relief valve/disc assembly at the top of the tower - so to read the gauge the operator ascends the tower’s stairs. On this occasion, the operator approaches the top of the stairway and hears the high-pitched sound of escaping fluid. The operator, anxious to identify the leak source so as to provide a more complete report to the supervisor, decides to continue climbing, searching for the source of the noise. The leak rate increases as the operator gets closer, then the escaping flammable vapor suddenly ignites causing burns to the operator in the resulting radiant heat.

In an accident investigation of the event, some key questions are raised. Did the operator assess the risk? If so, what did the operator perceive his exposure to this risk to be upon noticing that something was “not quite right”? Why did he decide to take that course of action? And, did the Process Hazard Analysis team members fulfill their responsibility to identify the hazards of this operation?

The Operator’s Perspective

The operator may have chosen the path taken as a result of not pausing to think about the possible consequences of continuing forward. The operator related to the accident investigation team that he had previously climbed these stairs hundreds of times without anything unforeseen occurring. Over the years, the operator became complacent about his proximity to the potentially dangerous equipment. Also, the operator may have assumed that diligence in following procedures would preclude injury. In addition, the operator knew that there were a number of plant safety systems that he thought he could depend on to minimize his exposure. He had acquired a certain level of comfort over his years in this plant. His assessment of the risk of this task: Low.

The Plant Engineer’s Perspective

The plant engineer, whose responsibilities include the safe and efficient operation of the unit in which the fractionation tower is an integral part, is also responsible for ensuring that the operations department personnel are not exposed to unnecessary risk in performing their assigned duties. From the engineer’s perspective, the leak is highly unexpected. The engineer was responsible for ensuring that the tower was pressure-tested for leaks prior to recommissioning at the last turnaround. Her assessment of the risk of this task: Low.

Perspective of the Risk Analyst (The Watchdog)

The risk analyst is frequently called upon to provide his expertise during the unit’s Process Hazard Analyses and Job Safety Analyses. It is necessary that he take an outsider’s view even if consulting with the plant from within the company. Perhaps because of his independent viewpoint, he may be expected to provide a more accurate estimate of risk, but this depends heavily on the risk analyst’s experiences. During the analyses, he guides the team in the discussion of the possibility of leaks and, before making his own assessment, listens carefully to the comments made by other team members, including operations and engineering department representatives.

What About The Biases In This Case?

In this case, the operator’s comments are revealing. Perhaps because the operator had performed the task of reading the tower pressure routinely with no untoward event, he had become acclimated to the dangers present. The operator, as expected, related to the team his individual experiences with leaks. This has the effect, perhaps unintended, of introducing a bias into the PHA team’s assessment of the risk of the hazard discussed. The team’s risk exposure assessment then differed from an independent analytical and objective assessment of that same risk.

The plant engineer’s contributions for the tower leak scenarios did not divulge any design flaws. She noted that the tower had not been a source of problems previously and that the metallurgy was adequate for the service. She had assumed that the existing design, with its overpressure protection system functioning properly, was adequate to circumvent any possible cause for leaking during operation. Although she was aware of the need during tower operation for periodic checks of the pressure, she made no assessment of the alternatives because of her evaluation of the risk as low.

The risk analyst’s judgment of the scenario may be somewhat tempered by these remarks, but he realizes that he is required to provide his objective assessment, a “composite” or industry viewpoint, relating to leaks in this service. He may acknowledge that leaks had not arisen in this unit previously, but has had experiences elsewhere that cause him not to dismiss the leak scenario as quickly as the others had. Even so, since he typically doesn’t have “veto” authority, his voice is but one in a handful of others which may statistically diminish his input. His assessment of the risk of this task: Moderate.

Risk Biases

The team consensus decision to assign an overall low risk to the event thwarted any attempt the Risk Analyst might have made to preclude it. The operator and engineer were subject to biases as a result of risk habituation, or the habit of becoming accustomed to an environment where hazards are perceived to be low, whether or not they in fact are.

On the other hand, workers may tend to overestimate the risk when assessing a scenario that has some factor of trepidation associated with it. An example might be entering a vessel for internal inspection following a similar inspection where a worker was asphyxiated.

Biases in risk perception may be introduced into hazard analyses for a number of reasons. Risk assessment team members may:

1. Be accustomed to the hazards imposed by their everyday work routines without experiencing an accident,
2. Have a general lack of knowledge or inadequate training in the hazards in their workplace,
3. Be subject to psychological influences - a sense of foreboding of an impending accident,
4. Fail to consider the “not-so-obvious” risk scenarios, while focusing on the “easier” issues.

Means to Reduce Risk Biases

Assessing risk of scenarios generally is a two-step process. It involves either a qualitative or quantitative assessment of the consequence, then the likelihood. Acquiring the information quantitatively (so many occurrences in 10 years, for example) is not often accurate, especially for events that are remote. Chances are that a more accurate assessment of both “consequence” and “likelihood” is made when a semi-qualitative scheme is used (e.g. inhalation hazard to 1-5 people; 1-10 occurrences in 10 years).

Other means to avoid biases in your risk assessments:

1. Train your operating personnel using predictive hazard analysis results,
2. Conduct risk assessments using knowledgeable, trained staff,
3. Require participation by both hands-on and highly experienced operating personnel in risk assessment,
4. Have risk assessments reviewed by independent qualified personnel,
5. Ensure independence and objectivity of team leadership,
6. Guard against teams being influenced by management to limit the scope of remedial measures for cost or other reasons,
7. Consider previous related incidents within the plant, and outside the organization, as part of the risk assessment process.

Thoughts or comments?

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