Video summary

Wake Up Call: Refinery Disaster in Philadelphia

Main summary

Key takeaways

News and Commentary

Incident Overview (June 21, 2019)

On June 21, 2019, the Philadelphia Energy Solutions (PES) refinery suffered a catastrophic failure in its hydrofluoric acid (HF) alkylation unit. A severely corroded pipe elbow ruptured, releasing process fluid (mostly propane with a small amount of HF). The escaping vapor ignited, triggering a major fire and multiple explosions.

The incident:

  • Released more than 5,000 pounds of highly toxic HF
  • Propelled large vessel fragments offsite, including a 38,000-pound fragment across the Schuylkill River
  • Caused an estimated $750 million in property damage
  • Despite the refinery’s dense urban location, authorities reported no known serious offsite health impacts

Investigation Findings (Chemical Safety Board)

The investigation, led by the U.S. Chemical Safety Board (CSB), concluded that a key community-protection safeguard did not work as intended.

Mitigation system failure

  • The HF mitigation water spray system could not be activated remotely.
  • A fire knocked out communication and backup power to the system.
  • About 40 minutes after the release began, a worker later had to manually start the system—allowing HF to vaporize and escape for a prolonged period.

The CSB emphasized the event should serve as a “wake-up call” to both the industry and regulators.

Five Main Safety Issues Identified by the CSB

  1. Mechanical integrity / corrosion management failure

    • The elbow failed due to accelerated corrosion driven by high residual metal content (nickel and copper), making it more vulnerable in HF service.
    • The elbow was installed around 1973 with a higher-nickel/copper alloy and remained in service for over 40 years, corroding faster than adjacent piping.
    • PES and the prior owner did not inspect all carbon steel piping components susceptible to HF corrosion.
    • Response cited: CSB states that API later revised standards to require special emphasis inspection programs to detect accelerated corrosion.

  2. Failure to verify equipment safety after changes in standards (“good practice guidance”)

    • Over time, ASTM standards evolved such that the elbow’s metal composition no longer met requirements.
    • PES and the prior owner did not perform a comprehensive evaluation of installed older components to confirm they still met safety expectations.
    • Implication: New hazard knowledge requires reassessment of existing equipment, not only new builds.

  3. Lack of remotely operated emergency isolation valves

    • CSB found there were no emergency isolation valves installed to remotely stop nearby hydrocarbon sources from feeding the failure point.
    • These valves were also not explicitly required by then-current API guidance.
    • Recommendation: Update API standards to require remotely operated emergency isolation valves on relevant inlets/outlets for HF and certain hydrocarbon-containing vessels.

  4. Safeguard reliability problems (fire/explosion compromised mitigation)

    • The water spray mitigation system was a critical safeguard, but became inoperable remotely when its control components were damaged and backup power failed.
    • Recommendation: API should require protection of critical safeguards and their control components from fire/explosion hazards (e.g., radiant heat and flying debris).

  5. Inherently safer design not required

    • CSB highlighted that HF is uniquely hazardous: it vaporizes and can travel offsite (unlike sulfuric acid, which remains a liquid on release).
    • Alternative alkylation technologies exist (e.g., solid acid catalysts and ionic liquid catalysts).
    • Recommendation: EPA should require Process Hazard Analysis to include a safer-technology/alternatives review and risk prioritization for HF, with corrective actions as needed.

Call to Action

Overall, presenters argued the tragedy exposed weaknesses not only at PES, but also in:

  • Industry standards
  • Federal regulatory requirements governing HF alkylation safety

The call to action was for API, refiners, and EPA to implement the CSB recommendations to help prevent similar HF alkylation unit disasters.

Presenters / Contributors

  • Owens (CSB spokesperson / presenter)
  • Grim (CSB investigator / presenter)

Original video