Key Takeaways

Recurring Gaps Undermine Safety – Even after 30 years of OSHA’s PSM standard, common oversights in process hazard analyses (PHAs)—from incomplete overpressure evaluations to poor documentation—continue to expose facilities to preventable risks.

Detail Matters in Hazard Analysis – Quantifying scenarios, thoroughly evaluating relief discharge locations, fire potential, and all types of leaks helps teams avoid false assumptions and ensures safeguards are appropriately designed.

Stronger Systems Require Teamwork and Follow-Through – Effective PHAs depend on broad team participation, robust recordkeeping, and timely action on recommendations to turn hazard identification into true risk reduction.

When OSHA's Process Safety Management (PSM) standard took effect in 1992, it promised a new era of systematic hazard identification. Three decades later, process safety professionals are still witnessing the same critical oversights repeatedly compromising facility safety—oversights that have contributed to near misses, and far worse, major incidents.

Drawn from more than 40 years of field observations, 10 recurring process hazard analysis (PHA) misses pose significant risks to personnel, assets and communities. These fundamental gaps occur across industry sectors, ranging from petrochemicals to pharmaceuticals.

Each PHA oversight can result in insufficiently documented risk exposing facilities to the danger of operating under false assumptions about their safety. By identifying what is most commonly missed or insufficiently documented within PHA, facilities can improve their safety culture, proactively preventing failures, and averting catastrophic incidents—ultimately preserving their license to operate and saving lives.

Critical Miss 1: Stopping at Overpressurization

Too many PHA teams stop their analysis at identifying "potential overpressurization" without providing the necessary detail to define the extent of the overpressurization. For example, there is a crucial difference between a vessel experiencing 1.3 times its maximum allowable working pressure (MAWP) and 3.5 times its MAWP.

At 1.3 times MAWP, a vessel might experience stresses that exceed its design limits but may remain structurally intact, with only localized deformation such as bulging or yielding. In such an overpressure situation, catastrophic failure of the vessel is not guaranteed.

At 3.5 times MAWP, a vessel is almost certain to experience catastrophic failure, as such stresses far exceed design capacity. This could result in a rupture or explosion with devastating consequences, posing severe risks to personnel (potentially resulting in multiple fatalities), equipment (often incurring significant financial losses), and the environment (with far-reaching impacts on both the surrounding community and local ecosystems).

Quantifying the overpressure scenario would address this gap. Facilities must specify the expected level of the pressure excursion, describe potential consequences in detail and consider cumulative fatigue damage from repeated moderate overpressure events. This level of detail enables proper safeguard evaluation and risk mitigation.

Critical Miss 2: Not Evaluating Relief Discharge Location

Relief devices prevent overpressurization, but evaluating where that relief goes, i.e., the relief discharge location, matters just as much. PHAs routinely evaluate relief device sizing and case consideration while sometimes overlooking the potential discharge location hazards. As per the PSM requirements, a PHA must address all process hazards.

Consider a relief valve venting hot flammables near a normally occupied control room. The device may protect the vessel as intended, but the discharge location could create an entirely new, and potentially catastrophic, risk scenario.

Creating separate PHA scenarios to evaluate relief discharge locations specifically closes this gap. Facilities must evaluate ignition sources, personnel exposure potential and dispersion characteristics to determine whether the discharge location is safe.

As an example, the following verbiage could be used to document an atmospheric discharge location for a relief device:

Potential for Relief Device XYZ to activate due to overpressurization. Relief Device XYZ vents outside at the roof of Building A on the structure's north side. Potential exists for the release of hot flammables at this location. However, this location has been evaluated and determined to be safe for the following reasons:

There are no known ignition sources in the vicinity of the discharge location.
The discharge point is located more than XX feet above the roof, allowing for adequate dispersion and eliminating the potential for personnel exposure to the hot material.

In summary, the discharge location of Relief Device XYZ poses no risk of ignition or personnel exposure.

Critical Miss 3: Inadequate Fire Documentation

Fire and explosion scenarios represent some of the highest-consequence process safety hazards, yet they are often overlooked or lack sufficient detail for effective consideration within PHAs.

Teams may acknowledge fire potential without exploring the escalation scenarios that make headlines. Additionally, not all fire/explosion scenarios carry the same level of risk, and documentation should reflect the severity of the specific hazard. A vessel rupture during an external fire near a control room housing multiple personnel demands far different safeguards than a small equipment fire in an isolated area.

Detailed fire scenario documentation that includes escalation potential, proximity to occupied areas and specific consequences builds resilience and lowers hazardous risk. This level of detail enables PHA teams to understand the magnitude of the hazard clearly and is essential for evaluating whether existing fire protection is adequate.

Critical Miss 4: Failure to Consider All LOPC Events

PHAs frequently miss documenting all potential leakage scenarios and their associated hazards, leaving gaps in the analysis and risk mitigation process. Loss of primary containment (LOPC) events include, but are not limited to, flange or packing leaks, drain valve failures, corrosion-induced releases, pinhole leaks between rupture disks and relief valves, etc.

Each LOPC represents a different risk profile requiring specific safeguards. In some cases, the PHA team may not understand the full implications of the potential LOPC. For example, if a pinhole leak develops in a rupture disk located upstream of a relief valve, process gases could slowly leak through the disk, leading to pressure buildup on the downstream side. This buildup could prevent the rupture disk from bursting at the appropriate pressure during a potential overpressure situation. In other cases, leakage to the environment may be overlooked entirely. While durable design can help minimize the likelihood and extent of leakage, PHAs must discuss and document the risks associated with both small and large process leaks.

PHA teams should systematically evaluate all potential LOPC events and include specific leak rates, locations and consequences. Additionally, sampling operations should be explicitly discussed, as it is one of the few times a process is intentionally opened, which increases risk exposure to hazardous chemicals.

Critical Miss 5: Insufficient Previous Incident Documentation

OSHA requires PHAs to address previous incidents with catastrophic potential, yet many teams discuss these events during meetings without documenting the discussions in the PHA record. This omission can hinder the ability of future teams to learn from past events and work to ensure safeguards are in place to prevent recurrence.

When incidents occur despite existing safeguards, they signal either unidentified hazards or failed safeguards, which are critical PHA inputs.

To demonstrate adherence to this requirement, it is advisable to document previous incidents within the PHA explicitly. Use keywords like "Previous Incident" in PHA documentation, preferably at the relevant scenario, and include incident dates, tracking numbers, brief descriptions and potential “worst-case” consequences (e.g., personnel injury did not occur because of the actual incident but could have manifested under different circumstances). This creates an auditable record and enables proper risk assessment.

Critical Miss 6: Missing Management of Change Documentation

The absence of Management of Change (MOC) documentation during a PHA can significantly compromise the safety and integrity of industrial operations. MOC documentation confirms that any modifications to processes, equipment or procedures are properly evaluated for potential safety risks. Without proper MOC records, changes made during the operation of a plant or facility may go unchecked, leading to unaddressed hazards, faulty risk assessments, inaccurate process safety information and incomplete hazard analyses.

For example, when a restriction orifice removal invalidates relief device sizing or new control valves change process dynamics, the PHA must reflect these changes; otherwise, risk exists but goes unaddressed.

Without MOC integration, PHAs become obsolete documents that do not reflect actual operating conditions. Documenting relevant MOCs using clear identifiers and tracking numbers is vital. Facilities should cross-reference MOCs within hazard scenario documentation so that all change-related risks are captured and evaluated as part of the PHA.

Critical Miss 7: Inadequate Hazard Identification

PHA teams often dismiss high-consequence scenarios as "double jeopardy," thereby talking themselves out of discussing and documenting such scenarios. The Center for Chemical Process Safety defines double jeopardy as the concurrent incidence of two independent initiating events or other revealed failures. A major incident like Piper Alpha, which is often attributed to the premature startup of a pump, actually resulted from multiple, seemingly independent failures occurring simultaneously. Processes are typically designed to tolerate single failures. They fail when multiple errors align—precisely the scenarios often dismissed as unlikely or excluded as “double jeopardy.”

To address such gaps, facilities may focus some potential hazard scenarios on the consequences rather than fixating on the initiating causes. By assuming that the "bad thing" happens and identifying what can be done to detect and minimize its impact regardless of the initiating cause, teams are less likely to overlook scenarios and more likely to identify safeguards to address them.

Another common oversight is neglecting the role of human error in process safety. This includes operator mistakes, procedural non-compliance or insufficient training, all of which can significantly contribute to accidents. A PHA should consider not only mechanical or chemical hazards but also how human actions or inactions might impact the process. Proper consideration may dictate that safety critical steps require sign-off or supervisor verification.

Critical Miss 8: Insufficient Team Involvement

To that end, PHAs are not solo exercises. They require diverse perspectives from operations, engineering, maintenance, safety and management. Missing any key stakeholder can result in blind spots that prove costly.

Operators, for example, know firsthand how the process works and may identify hazards or operational risks that others, such as engineers, might overlook in their design documents. Management also plays a critical role in the team by reinforcing the importance of the PHA process as well as allocating time, resources and the personnel necessary for a thorough analysis. Their presence, especially at the initial PHA session, underscores a commitment to prioritizing process safety, accountability and collaboration.

Facilities should strive to include all necessary participants whenever feasible. It is far better to delay the process until the right people are in the room than to proceed with insufficient involvement. Rushing the PHA or excluding key stakeholders can lead to incomplete analyses, which may have catastrophic consequences.

Critical Miss 9: Inadequate Documentation and Recordkeeping

PHAs generate critical safety information, yet results are often inadequately communicated, or in some cases not communicated at all, leaving personnel unaware of potential hazards and mitigation measures. Poor documentation practices compound the problem, creating compliance gaps and operational oversights.

To address these issues, facilities must implement robust documentation and communication practices to help ensure that PHA results are effectively recorded, shared and maintained. Implementing robust action item tracking systems and establishing regular review cycles also help keep PHAs current and relevant.

Critical Miss 10: Lack of Follow-Up or Improper Decline of PHA Action Items

Identifying hazards is only part of the process—effective risk management requires that identified issues, including suggested action items, are addressed in a timely and systematic manner.

OSHA's PSM Compliance Directive, Process Safety Management of Highly Hazardous Chemicals – CPL 02-01-065, provides specific criteria for justifiably declining PHA recommendations. These criteria are as follows:

The analysis upon which the recommendation is based contains material factual errors.
The recommendation is not necessary to protect the health and safety of the employer’s own employees or the employees of contractors.
An alternative measure would provide a sufficient level of protection.
The recommendation is infeasible.

Unfortunately, many organizations ignore these requirements, often declining PHA recommendations without referencing any of the above rationales. This leaves hazards unaddressed and creates potential compliance and safety risks.

As per OSHA's PSM standard and EPA's Risk Management Program (RMP) rule, PHAs must be revalidated at least once every five years. Facilities should establish clear action plans with assigned responsibilities and timelines, allocate sufficient resources to address identified gaps, and conduct follow-up audits to verify effectiveness.

The Bottom Line

PHAs are a cornerstone of effective PSM, but their success hinges on thoroughness, attention to detail and a commitment to continuous improvement. These 10 common PHA misses deserve attention as they continue to undermine the effectiveness of analyses and increase the potential for catastrophic incidents.

Ultimately, every PHA's goal should be to proactively identify and mitigate risks, upholding lessons learned from past incidents and addressing all potential hazards. ⊕