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Valero Delaware City Refinery Asphyxiation Incident

Overview

Two contract employees were overcome and fatally injured by nitrogen while performing maintenance work near a 24-inch opening on the top of a hydrocracker unit reactor. One worker died after entering or falling into the nitrogen-filled reactor, and a second worker died while attempting rescue.

Incident Snapshot

Field Value
Facility / Company Valero Energy Corporation
Location Delaware City, DE
Incident Date 11/05/2005
Investigation Status The CSB issued a case study report and a safety video based on this incident at a news conference in Newark, Delaware, on November 2, 2006.
Accident Type Confined Space / Asphyxiation
Final Report Release Date 11/02/2006

What Happened

  • A few days before the incident, Matrix installed a temporary nitrogen supply system on the hydrocracker unit reactor (R1).
  • Valero operators opened the nitrogen valve about one or two turns to provide a nitrogen purge inside R1 as part of the catalyst loading procedure.
  • The nitrogen flowed slowly out of the reactor through the top manway, the only open discharge point on the reactor.
  • Two days before the incident, workers employed by Catalyst Handling Services Corporation finished loading the reactor with the new catalyst and placed a temporary plastic tarp and wooden cover over the open manway.
  • About five hours before the incident, a CHSC foreman wrapped red danger tape around the studs.
  • A Valero hydrocracker unit operator issued a safe work permit to a Matrix nightshift boilermaker crew to install the top elbow, or pipe assembly, on R1.
  • The permit was not amended to limit the work to set up only.
  • The nitrogen purge status was marked N/A on the permit even though the reactor continued to be purged with nitrogen.
  • At about 11 p.m., two Matrix boilermakers removed the wooden cover and plastic tarp and cleaned the manway flange surface.
  • While the boilermakers were cleaning the manway flange surface, a Matrix pipefitter told them that a roll of duct tape was lying on the distribution tray about five feet below the opening.
  • The boilermakers discussed retrieval options with their foreman and decided to make a long wire hook and lower it through the manway to retrieve the tape.
  • A few minutes before the incident, nearby workers saw the first victim standing next to the studs surrounding the open manway trying to retrieve the tape with the wire.
  • One worker saw him kneeling next to the studs while he worked with the wire.
  • Nobody saw him enter the nitrogen-filled reactor, but he either fell in or intentionally went into the reactor.
  • An eyewitness saw the boilermaker foreman and the nightshift contract administrator looking through the manway into R1.
  • The eyewitness watched the foreman hurriedly grab a ladder, insert it into the reactor, and immediately climb down.
  • The eyewitness next saw the nightshift contract administrator approach the ladder, hesitate, and then urgently call for help on his radio.
  • The site emergency siren then activated.
  • Valero Emergency Response Specialists and Matrix safety personnel arrived on the platform in less than two minutes and saw two victims lying motionless inside the reactor on the tray five feet below the manway.
  • They inserted an oxygen meter through the manway and it immediately alarmed; the oxygen concentration was near zero.
  • A Valero operator put on his self-contained breathing air respirator then entered the reactor to help the two victims.
  • An Emergency Response Specialist asked a contractor loading catalyst into the adjacent reactor to put on his supplied breathing air helmet and climb down the ladder into the reactor to help the operator.
  • Rescue workers wrapped a confined space recovery tripod hoist cable around each victim and lifted them out one at a time.
  • The two victims were deprived of adequate oxygen for nearly ten minutes.
  • Once on the work platform, an emergency medical technician examined each victim; however, both were unresponsive and efforts to revive them unsuccessful.
  • They were transported to the hospital where they were pronounced dead.

Facility and Process Context

  • Valero Energy Corporation acquired the Delaware City refinery from Premcor Refining Company, Inc. in September 2005.
  • The Delaware City refinery processes 180,000 BPD at the 5,000-acre complex and has about 570 employees.
  • During the turnaround, Valero refinery unit operators retained responsibility for unit shutdown, control and removal of hazardous chemicals from equipment, and equipment lock-out and tag-out.
  • Valero operators prepared, reviewed, and approved all contractor work permits, including safe work, hot work, and confined space access control, in accordance with the Valero site procedures.
  • Valero assigned a contract administrator to each turnaround work shift.
  • The dayshift and nightshift contract administrators were responsible for expediting the work, reporting progress to the Valero turnaround manager, monitoring safety and health issues, and coordinating the work among the turnaround contractors.
  • Matrix was contracted to provide pipefitters, boilermakers, and other skilled labor needed for the turnaround.
  • Matrix and the other contractors were responsible for providing skilled craftspeople with general industrial and refinery-specific safety training.
  • Contractors were required to incorporate all Valero refinery safety policy requirements in their safety procedures.
  • Matrix was responsible for preparing written work permit requests for the assigned tasks, submitting them to the Valero unit operators, and reviewing the scope of each permit and listed safety prerequisites with the Valero permit preparer.
  • After the work permits were approved by a Valero unit operator, the Matrix boilermaker foremen reviewed the permit with the assigned work crew before starting the activity.

Consequences

  • Fatalities: 2 contractor employees died.
  • Injuries: None reported.
  • Environmental release: None reported.
  • Facility damage: None reported.
  • Operational impact: The reactor was being purged with nitrogen during catalyst loading and pipe reassembly work; emergency responders closed the nitrogen supply valve the night of the incident.

Key Findings

Immediate Causes

  • The first worker was overcome by nitrogen and collapsed in the vessel.
  • The crew foreman was asphyxiated while attempting to rescue him.
  • Nitrogen gas displaced the oxygen, creating an oxygen-deficient atmosphere.

Contributing Factors

  • The nitrogen purge continued to vent through the top manway.
  • A nitrogen purge warning sign and barricade were not in place in the work area.
  • The permit was not amended to limit the work to set up only.
  • The nitrogen purge status was marked N/A on the permit even though the reactor continued to be purged with nitrogen.
  • The boilermakers' safe work permit did not inform them that the reactor was on nitrogen purge.
  • The Valero permit-preparer did not specify fresh-air work restrictions on either crew's safe work permit.
  • The Valero and Matrix workers interviewed by the CSB investigators stated that their training did not address the possibility that an oxygen-deficient atmosphere might be present outside the confined space near the access opening.
  • The Valero refinery safe work procedures required operators to install a barricade and post warning signs at all equipment access points before the nitrogen purge was started, and to list all personnel working inside the barricaded area using a controlled area entry log, but these were not used at the R1 manway the night of the incident.
  • The wooden cover did not prevent the nitrogen from venting out of the manway.
  • The manway opening was only 24 inches and the victims were not wearing safety harnesses, making recovery difficult.

Organizational and Systemic Factors

  • Contrary to the procedure requirement, the work permit issued to the Matrix boilermaker foreman on November 5, 2005 to install the pipe assembly was approved without first conducting this safety-critical jobsite visit.
  • The Valero and Matrix worker training did not address the possibility that an oxygen-deficient atmosphere might be present outside the confined space near the access opening.
  • The CSB found that neither the industry safety guidelines nor the Valero corporate guidelines, site procedures, or associated training material adequately address the risk of asphyxiation caused by possible nitrogen accumulation outside the confined space during a nitrogen purge.
  • The Valero site procedure for permit-required confined space entry required all open, permit-required confined space access points to be clearly identified with a warning sign.
  • The OSHA confined space standard does not specifically address situations where atmospheric hazards may be present directly outside a confined space access opening.

Failed Safeguards or Barrier Breakdowns

  • a nitrogen purge warning sign and barricade were not in place in the work area
  • the permit was not amended to limit the work to set up only
  • the nitrogen purge status was marked N/A on the permit even though the reactor continued to be purged with nitrogen
  • the boilermakers' safe work permit did not inform them that the reactor was on nitrogen purge
  • the Valero permit-preparer did not specify fresh-air required on their permit
  • the Valero site fresh-air work procedure was not specified on either crew's safe work permit
  • the barricade and control log were not used at the R1 manway the night of the incident
  • no warning sign was in place at the time of the incident
  • the wooden cover was not intended to, and did not prevent the nitrogen from venting out of the manway
  • the foreman did not remain on the platform and instead climbed into the reactor
  • the victims were not wearing safety harnesses

Recommendations

  1. 2006-02-I-DE-R1 — Recipient: Valero Delaware City Refinery — Status: Not specified — Summary: Conduct safe work permit refresher training for all permit-preparers and approvers and affected refinery personnel and contractors. Emphasize: All proposed work requires a jobsite visit by the requestor and a unit operator to identify special precautions, equipment status, and personal safety equipment requirements. The conditions for marking the “nitrogen purge or inerted” (Yes/No/NA) status box. The permit must clearly identify all hazards and special personal protective equipment requirements. “Fresh Air” work restrictions apply to “Set up only” permits whenever an IDLH atmosphere is suspected or known to be present in the work area.
  2. 2006-02-I-DE-R2 — Recipient: Valero Delaware City Refinery — Status: Not specified — Summary: Conduct confined space control and inert gas purge procedure refresher training for all affected refinery personnel and contractors. Emphasize: warnings at all access points to confined space temporary openings. warnings, barricades, and access control log at equipment during purging. overcome. procedures.
  3. 2006-02-I-DE-R3 — Recipient: Valero Energy Corporation — Status: Not specified — Summary: Audit work permit procedures and nitrogen purge safety procedures at each Valero U.S. refinery. Determine if issues identified in this Case Study are occurring elsewhere. Implement corrective action, including training, where necessary.
  4. 2006-02-I-DE-R4 — Recipient: Valero Energy Corporation — Status: Not specified — Summary: Require Valero U.S. refineries to revise and conduct nitrogen hazards awareness training. Emphasize: overcome. procedures.
  5. 2006-02-I-DE-R5 — Recipient: Matrix Service Industrial Contractors, Inc. — Status: Not specified — Summary: Conduct confined space control and inert gas purge procedure refresher training for all affected personnel. Emphasize: warnings at all access points to confined space temporary openings. The need to maintain posted warnings, barricades, and access controls as required by the client. overcome. procedures.
  6. 2006-02-I-DE-R6 — Recipient: American Petroleum Institute — Status: Closed – Acceptable Action — Summary: Revise Guidelines for Safe Work in Inert Confined Spaces in the Petroleum and Petrochemical Industries (API, 2005) to clearly address the following: An oxygen-deficient atmosphere rapidly overcomes the victim. There is no warning before being overcome. An oxygen-deficient atmosphere might exist outside a confined space opening. Rescuers must strictly follow safe rescue procedures.
  7. 2006-02-I-DE-R7 — Recipient: American Society of Safety Engineers — Status: Closed – Exceeds Recommended Action — Summary: Revise Safety Requirements for Confined Spaces, ANSI/ASSE Z117.1, to emphasize that an oxygen-deficient atmosphere rapidly overcomes the victim, there is no warning before being overcome, an oxygen-deficient atmosphere might exist outside a confined space opening, and rescuers must strictly follow safe rescue procedures.
  8. 2006-02-I-DE-R8 — Recipient: Compressed Gas Association — Status: Not specified — Summary: Issue a safety alert to address nitrogen/inert gas hazards in confined spaces. Emphasize that: overcome. procedures.

Key Engineering Lessons

  • Nitrogen purge gas can accumulate outside a confined space opening and create a lethal oxygen-deficient atmosphere near the access point.
  • Temporary covers such as a wooden cover and plastic tarp may not prevent nitrogen from venting through an open manway.
  • Work permits must accurately reflect purge status and required personal protective equipment when inert gas is present.
  • Access-point warnings, barricades, and controlled-area logs are necessary safeguards during nitrogen purging operations.
  • Rescue attempts into an oxygen-deficient atmosphere can create a second fatality if safe rescue procedures and respiratory protection are not followed.

Source Notes

  • Priority 1 final report used as the primary authority for incident facts and findings.
  • Priority 4 supporting statement used only where consistent with the final report.
  • Priority 4 recommendation status pages used to confirm final status for recommendations R6 and R7.
  • Some recommendation summaries in the source text were truncated or garbled; summaries were preserved only to the extent explicitly provided.

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