Technical Blog
Known Hazards, Unknown Risks: Closing the Gap in Process Safety
In the world of process safety, we often find ourselves dealing with hazardous situations that are often discussed and well-documented yet still lead to unexpected incidents. The challenge isn’t necessarily in agreeing that certain situations contain hazards but rather in sifting through the myriad of scenarios that could occur and identifying the highest hidden risks that accompany them. A striking example of this is the increased likelihood of process safety incidents and risk during transient operations such as startup and shutdown.
Understanding the Risk: The Data Speaks for Itself
According to the Center for Chemical Process Safety (CCPS), process safety incidents occur five times more often during startup than during normal operations. A 2010 study in the refining industry further supports this, showing that 50% of process safety incidents happen during startup, shutdowns, and other infrequent operations.
Historical case studies emphasize these trends:
- Texas City, TX (2005) – An explosion during startup resulted in 15 fatalities and 180 injuries.
- La Porte, TX (2014) – A shutdown-related incident led to 4 fatalities.
- Torrance, CA (2015) – A near miss with no injuries, but the potential for catastrophic consequences.
These incidents highlight that transient operations present a unique risk profile—one that requires a different approach to hazard identification and mitigation.
Why Are Startup and Shutdown So Hazardous?
Unlike normal operations, startup and shutdown involve rapidly changing process conditions, making it difficult to predict outcomes. Several factors contribute to the increased risk:
- Dynamic Process Parameters – Conditions fluctuate rapidly, introducing instability.
- Non-Routine Operations – Operators may not be as familiar with startup/shutdown procedures.
- Bypassed or Manually Set Process Controls – Safety systems may be temporarily disabled or overridden.
- Latent Failures in Safeguards – Critical safety systems may be isolated or not functioning as expected.
- Increased Occupancy in Hazardous Areas – Occupancy factor may not be applicable or more people may be in the affected area.
None of this should surprise anyone in the industry – we all talk about start-up and shutdown being the most hazardous time in the plant. With the data, incidents, and even our own water cooler talks all pointing to the same answer, one would expect that our risk assessments paint the same picture – right?
Findings from PHA Studies
At Cognascents, we have analyzed multiple Process Hazard Analyses (PHAs) across the upstream, midstream, and downstream sectors, identifying a disconnect between documented risks and actual field conditions.
More than 75 percent of the studies Cognascents has received from clients for our review have less than 10 start-up/shutdown scenarios identified across the entire study. The studies looked at were not small project PHAs but averaged 28 nodes in length. Even though Cognascents’ based PHAs had a better skew, even our numbers fell short of the hazards that are truly present in the field – so that left us wondering why this was occurring.
- Startup and shutdown deviations are often at the bottom of each node.
- That means the team had just completed assessment of every valve opening and closing, every pump tripped, loss of each utility, loss of each heat exchanger, etc. in normal operation. By the time the team has reached the bottom of the node, it is easy to think “We have already talked about everything we can, let’s move on to the next node”.
- Teams will have experienced operators in the room, but it is less common to have the actual procedures in hand.
- Without physically picking up the procedures and reading through them in a risk assessment mindset, scenarios will simply get missed.
- Procedural reviews are inherently a different workflow and thought process than a normal operations risk assessment. It is challenging to switch in and out of the different mindsets/methodologies.
Closing the Gap: Proposed Solutions
- Enhancing PHA Methodology – Incorporate specialized guide-words such as “skipped step,” “steps performed out of order,” “too long” and “too short.”
- Procedure-Based PHA Reviews – Ensure that startup and shutdown procedures are reviewed during PHA sessions while utilizing PHA guidewords, while at least being in a separate node from the normal operations.
- Targeted Follow-Up Studies – Conduct follow-up reviews focused specifically on transient operations after PHA revalidations.
By adopting these strategies, organizations can better anticipate and mitigate the risks associated with startup and shutdown operations—ultimately preventing incidents before they occur. Even if its not with the addition of new safeguards, these types of transient operations studies often find ways to improve the procedures themselves. This can lead to increased clarity and real world risk reduction without any costly changes in the field.
At Cognascents, we are committed to advancing process safety by closing the gap between hazard identification and real-world operational risks. If you’d like to collaborate on this topic or discuss how we can support your PHA efforts, let’s connect.
Meet the Author
Jeffrey Miller, P.E. – Technical Manager – PHA & PSM
Jeffrey is an experienced chemical engineer specialized in the area of process hazard analysis, pressure relief analysis, alarm rationalization, operating procedures generation, process simulation, and MOC implementation. He has experience facilitating facility-wide PHAs, leading HAZOP and LOPA revalidation efforts, and assisting in the development of PHA guidance documents.
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