Deconstructing the Marathon Incident: Key PHA Lessons for Fired Heater Safety

The Marathon Martinez Incident: A Cascade of Preventable Failures

What began as a routine startup of a renewable diesel hydroprocessing unit quickly spiraled into catastrophe. A seemingly minor valve misalignment became the first domino in a chain of failures, culminating in a fired heater tube rupture and a devastating fire. The CSB investigation meticulously pieced together the sequence of events, pinpointing key contributing factors:

• Lesson 1: Valve Misalignment – The Initial Trigger: An inadvertently open valve ("Valve B") diverted process flow around the fired heater. As the CSB report notes, "Marathon Martinez’s failure to identify the potential for the flow diversion...contributed to the incident." This seemingly simple error initiated a chain reaction.
• Lesson 2: Afterburning – Unseen Escalation: Blocked air inlets on burners, combined with the flow diversion, led to incomplete combustion and dangerous afterburning in the heater's convection section. This caused temperatures to skyrocket, weakening the heater tubes beyond their design limits.
• Lesson 3: Inadequate Safe Operating Limits – Blind to Danger: Critically, "Marathon had not equipped the fired heater...with adequate safe operating limits (Not-to-Exceed limits) and alarms to alert personnel that the tube metal temperatures had exceeded their mechanical design limits..." (CSB Report). The absence of proper alarms left operators blind to the escalating danger.
• Lesson 4: Worker Proximity – Placing Personnel in Harm’s Way: Troubleshooting procedures required a field operator to be dangerously close to the fired heater, directly in the line of fire when the inevitable tube rupture occurred. The CSB stresses, "The field operator was at risk when the fired heater tube ruptured because he was standing directly next to the heater..."
• Lesson 5: Defeated Safety Instrumented System (SIS) – False Sense of Security: The flow diversion bypassed the flow meter, rendering the low-flow SIS ineffective. The system designed to protect against low flow conditions was unknowingly circumvented, providing a false sense of security.

The human cost of this incident is immeasurable: a worker endured third-degree burns over 80% of his body, facing months of critical care and rehabilitation. The financial toll, estimated at $350 million in property damage, is staggering. These are not just numbers; they represent real lives and livelihoods profoundly impacted. This tragedy underscores the urgent need for robust PHA to move beyond reactive responses and embrace proactive, preventative strategies.

Key Lessons from the CSB Recommendations

The CSB report offers a clear and actionable roadmap for preventing similar incidents. These recommendations, targeted at Marathon and the broader industry, provide invaluable insights for strengthening your process safety programs. Let's examine the key lessons and how you can apply them:

Lesson 6: Engineering Safeguards for Afterburning and Overheating (CSB Recommendation R1 & R6b)

• CSB Recommendation: Implement engineering safeguards to detect and prevent afterburning, including combustibles monitoring (like Tunable Diode Laser analyzers), flame detectors, and comprehensive thermocouple instrumentation. The CSB recommends that API update API RP 556...with engineering safeguard requirements (“shall” rather than “should” language) to detect and prevent afterburning in fired heaters.
• Why it matters: Afterburning is a silent killer in fired heaters. Relying solely on temperature monitoring may be insufficient. Combustibles monitoring and flame detection provide early warning signs of incomplete combustion, enabling proactive intervention before temperatures reach critical levels. Your PHA must rigorously analyze scenarios leading to afterburning and evaluate the necessity of these advanced safeguards.
• Practical Application: The What-If PHA Automated Excel Spreadsheet facilitates a systematic evaluation of afterburning scenarios. You can use it to analyze "What-If" questions like "What if burner air supply is blocked?" or "What if fuel/air mixture is incorrect?" The tool helps you document the need for safeguards like combustibles analyzers and flame detectors as layers of protection identified directly through your PHA study, aligning with CSB recommendations and industry best practices.

Lesson 7: Robust Safe Operating Limits and Alarms (CSB Recommendation R2 & R5)

• CSB Recommendation: Update corporate standards for Not-to-Exceed (NTE) Limits and Alarms, specifically for tube metal temperature alarming,, and ensure clear predetermined response actions, including remote heater shutdown and personnel evacuation. The CSB recommends that API revise API RP 556...with Requirements for proper response to high tube metal temperatures, including guidance to alert operators when safe operating limits are exceeded...
• Why it matters: Generic temperature alarms are insufficient. You need tube metal temperature NTE limits that trigger immediate, pre-defined actions, including automated shutdown and personnel evacuation protocols. As the CSB emphasizes, personnel continued troubleshooting because no Not-to-Exceed alarm activated, highlighting the fatal flaw in relying solely on generic alarms. Your PHA is the foundation for defining these critical limits.

Lesson 8: Reinforce "Walk the Line" Practices (CSB Recommendation R3)

• CSB Recommendation: Improve "Walk the Line" performance to ensure rigorous valve alignment verification before startup, enhanced shift communication regarding valve lineups, and reinforced training on "Walk the Line" concepts for all operations personnel and management. The CSB stresses the need to Reinforce Walk the Line concepts, including the expectation for only trained operators to control valve line-ups at their units, through training for all levels of management.
• Why it matters: Human error is inevitable, but its consequences can be mitigated. "Walk the Line" practices are essential for minimizing valve misalignments and other human-factor related errors. Training alone is not enough; you need structured procedures and verification processes embedded in your operational culture. The CSB report highlights that even management personnel were manipulating valves without proper training or communication, underscoring a systemic breakdown in procedural adherence.

Lesson 9: Comprehensive Gap Assessments and Corporate Oversight (CSB Recommendation R4 & R7)

• CSB Recommendation: Conduct comprehensive gap assessments of facilities against corporate safety policies, particularly focusing on Operating Limits, PHA, and PSM/RMP Operating Procedures. The CSB also recommends that Marathon Petroleum Corporation confirm the results of the Martinez facility’s comprehensive gap assessment...and conduct an Operations Excellence full assessment.
• Why it matters: Corporate standards are only effective if consistently implemented and rigorously audited across all facilities. The Marathon Martinez incident revealed a significant gap between corporate policy and site-level implementation. Regular, comprehensive gap assessments and robust corporate oversight are vital to identify and rectify these discrepancies before they lead to incidents. For safety inspectors, this emphasizes the need for thorough audits that go beyond surface-level compliance.
• Practical Application: Utilize the What-If PHA Automated Excel Spreadsheet as a standardized platform for conducting and documenting PHAs across your organization. The consistent framework and reporting features facilitate easier comparison of PHA studies across different units and facilities, enabling corporate oversight to identify potential gaps in risk assessment quality and implementation of safeguards. Furthermore, the tool's organized data structure aids in tracking action items and recommendations arising from gap assessments and audits, ensuring accountability and continuous improvement.

Implementing a Consistent PHA Framework

The lessons from the Marathon Martinez incident highlight the risks of relying on unstructured brainstorming. To address systemic failures—like afterburning or bypassed interlocks—teams need a rigorous method to document questions and track safeguards.

To support this process, we developed the What-If PHA Automated Excel Spreadsheet. It provides the administrative structure to organize the study, helping facilitators document scenarios and track recommendations to closure.

The tool includes a library of over 1,000 industry-relevant prompts, providing a baseline to assess your safeguards against known failure modes without starting from a blank page.