“Most people would rather have their wisdom teeth extracted without the benefit of anesthesia than sit through a PHA.”
PHAs are tough. They take focus and energy and they take people away from their regular jobs, which don’t go away just because they are in a PHA. Yet, like good dental hygiene, no one thinks PHAs are unnecessary. There are seven habits, though, that can make PHAs more meaningful and productive, and produce results that are more useful. Consider these before your next PHA.
- For each hazard, identify the real cause
The cause of a deviation is a failure—either a failure of a piece of equipment or an operator error. The cause is not identified until a specific failure is identified. Without a specific failure in mind, it is just about impossible to correctly estimate the likelihood of the hazard. For instance, “high temperature” should not be listed as the cause of high pressure. On the other hand, “temperature control loop fails high” could be listed as the cause of high pressure. It is a specific equipment failure. As for operator error, identify the specific error, not simply a generic “operator error.” Otherwise, how will the team estimate the frequency of opportunities to make the error, the probability that the opportunity will result in an error?
- Don’t call the failure of a safeguard a cause
The failure of a safeguard is not the cause of a deviation. Something else had to fail first to cause the deviation in the first place. For example, a pressure relief valve failing to lift is not what initiated a high-pressure hazard. Something else must have failed first. Likewise, the inability of an operator to respond to an emergency is not what created the emergency. Until you identify the failure that initiated the deviation, you haven’t found the cause.
- Don’t use “Double Jeopardy” to exempt scenarios
There was a time, early in the history of PHAs, that a scenario that required two things to go wrong was discounted as credible. “Oh, that’s double jeopardy.” As it turns out, two things can go wrong. Even three things. Or four. Don’t dismiss multiple failures as causes for hazards, just because of “double jeopardy”. The likelihood is much lower when more than one thing must fail, but a lower likelihood is not the same as impossible. Instead, consider the likelihood of more than one failure, and whether the failures must be simultaneous, or can occur sequentially.
- Think of consequences as events with impacts
“Consequence” is a sufficiently ambiguous term that it often confounds some PHA teams. It is helpful to split consequences into two parts. The first is an event; fires, explosions, and toxic releases are the big three events of process safety. The second part is the impact of that event on a receptor. Receptors include plant personnel, members of the public, the environment, and for some organizations, assets. It you define the event first, and then its impacts, the analysis is much cleaner.
- Think of a consequence as the “likely case”, not the “worst case”
Any hazard has the potential to be fatal. Someone could slip on a paper clip, fall and hit the back of their head against the corner of a desk, and then die. Does that make a paper clip a fatal hazard? What is the more likely impact of a paper clip?
There are also recorded cases of people surviving 30,000-ft falls from aircraft. Does that make such a fall anything less than fatal?
In any case, the term “worst case” is undefined. Is any event or impact “the worst”? No matter how awful the impact is that someone imagines, someone else can imagine something worse. Modifying the term to “credible worst case” isn’t much help, unless a definition of “credible” is well-developed. Does “credible” mean physically possible? Something that can occur once a year? 10 years? 100 years? Some level of likelihood must be considered; “most likely” is a term that everyone understands. When someone suggests that a hazard is potentially fatal, it is fair to accept the possibility and yet still ask whether they are talking about a paper clip.
- Match likelihood to the consequence
During the risk assessment it completes for each hazard, the team categorizes the consequence severity (the impact) and the likelihood (the frequency) of the final hazardous event. A gut check is very important at this stage. Teams are very good at imagining the event that a hazard could cause. They are not bad at imagining the impact of that event on various receptors. They are terrible at estimating likelihood. This is one of the reasons that LOPAs are so valuable. At the PHA, however, the team should do a gut check to make sure that the estimated likelihood for a hazardous event is consistent with the consequence severity that the team has settled on.
- Don’t make recommendations that don’t reduce risk
Finally, there are recommendations. One thing to keep in mind is that the primary purpose of a PHA team is to identify hazards. The group that is doing this may not be the best group to determine how to reduce risk if the hazards are too dangerous. So, consider recommendations as preliminary, even when the need to reduce risk is absolute. Keep in mind that every recommendation from a PHA requires follow-up. Recommendations from a PHA required by the PSM Standard or the RMP Rule have a legal mandate for follow-up. So, make sure that every PHA recommendation serves to reduce risk. If implementing a PHA recommendation will neither reduce the consequence severity (the impact) nor the likelihood (the frequency), the recommendation does not reduce the risk and does not belong in the PHA, no matter how good the recommendation is.
Changing Habits is Hard Work
Just as brushing and flossing regularly make visits to the dentist much less onerous, good PHA habits will make a PHA much less painful to endure. Good PHA habits will even lead to better results from the PHA. Remember that breaking bad PHA habits takes time and effort, so give yourself a break as you strive to develop new PHA habits. Even small steps in the right direction can make a difference over time. When you fall off the wagon, get back on. More effective PHAs will not only make your life easier, they will make your workplace safer.
