CSB Releases Safety Bulletin into 2015 Chemical Release and Flash Fire at the Delaware City Refining Company

Emphasizes Five Key Lessons for Incident Prevention When Preparing Process Equipment for Maintenance

U.S. Chemical Safety Board, May 18, 2017

The U.S. Chemical Safety Board (CSB) has released its findings and a safety bulletin entitled "Key Lessons for Preventing Incidents when Preparing Process Equipment for Maintenance" resulting from the 2015 hydrocarbon release and fire that injured one worker at the Delaware City Refining Company in Delaware City, Delaware.

CSB Chairperson Vanessa Allen Sutherland said, "More than a third the incidents investigated by the CSB occurred during maintenance activities, ultimately resulting in 86 fatalities and 410 injuries."

On November 29, 2015, alkylation unit operators at the Delaware City Refining Company, or DCRC, were preparing equipment for maintenance. Prior to performing the work, operators had to first drain and isolate a section of piping scheduled to be replaced by closing valves to block the flow of hydrocarbons into the piping.

However, the operators learned that a valve on one side of the pipe isolation was leaking and therefore would not seal properly, which led staff to expand the isolation to a downstream block valve.  That expansion did not trigger additional hazard review.  The next available valve included additional equipment not involved in the original isolation plan which needed to be drained to ensure complete removal of flammable hydrocarbons. 

The CSB determined that the work activity performed on the day of the incident was non-routine. That evening, shortly after opening the drain valve to the sewer system, the nightshift operator recalled hearing a pop and suddenly seeing a wall of fire advancing toward him. He suffered second- and third-degree burns from the flash fire.

Supervisory Investigator Johnnie Banks said, “Prior to the incident, DCRC did not have general procedures for preparing equipment for maintenance or procedures for taking those pieces of equipment out of service.  If DCRC had identified and addressed potential hazards before commencing this work, this incident would not have happened.” 

The CSB’s investigation identifies five safety lessons which can be applied to many high hazard facilities:

  1. Non-routine operational tasks surrounding maintenance should have standard operating procedures, covering tasks such as emptying, decontaminating, washing, steaming, purging, and draining equipment and vessels.
  2. For all equipment preparation activities, develop a process that requires preplanning and hazard identification prior to initiating the work.
  3. When isolating equipment for emptying or decontaminating activities prior to maintenance work, avoid reliance on single block valves. Always consider more protective measures for isolation such as including double blocks or blinds.
  4. When an equipment preparation task or isolation plan needs to be modified or expanded due to leaking valves or changing conditions, evaluate the hazard.
  5. Use closed systems such as tanks, drums, flares, control the draining, or relieving of hazardous energy in preparation to isolate equipment for maintenance.

Chairperson Sutherland said, "Non-routine operations warrant careful attention. The five key lessons from this safety bulletin will help ensure that hazards are identified, and addressed to promote safer operations during similar activities."

Click Here to View the Safety Bulletin

About the CSB

The CSB is an independent, non-regulatory federal agency charged with investigating serious chemical incidents. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems. The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website,

For more information, contact Communications Manager Hillary Cohen, cell 202-446-8094 or email

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