FLASH FIRE — EQUIPMENT DE-INVENTORYING FOR MAINTENANCE (SAFETY BULLETIN)
Delaware City Refining Company — Equipment Preparation for Maintenance
Delaware City Refining Company (DCRC)
📍 Delaware City, DE
Incident: November 29, 2015  •  CSB Report: May 18, 2017
0
Fatalities
Hydrocarbons (Kellogg HF Alkylation Unit De-inventorying)
Chemical Involved
0
CSB Recommendations
📋 Incident Summary

On November 29, 2015, an operator at the Delaware City Refining Company (DCRC) Kellogg Alkylation Unit suffered second degree burns to his face and neck while performing de-inventorying activities on a vessel in preparation for the removal of a pipe spool. This incident was one of three related incidents at the same facility in 2015 -- the others occurred on August 21 and August 28 -- indicating a systemic issue with maintenance preparation procedures.

The CSB issued a Safety Bulletin rather than a full investigation report with formal recommendations. The bulletin addressed the critical importance of proper process equipment preparation before maintenance, specifically the de-inventorying and isolation steps required to safely open or remove process connections in hydrocarbon service.

The Safety Bulletin communicated key lessons applicable across the refining industry: process equipment must be rigorously verified as de-inventoried and isolated before connections are opened; multiple similar incidents at the same facility signal a systemic procedure deficiency requiring management system correction; and atmospheric monitoring must be performed immediately before any process connection is opened, regardless of confidence in prior de-inventorying steps.

🔎 Key Findings
Finding 01
Operator Burned During De-inventorying Activities
An DCRC operator performing de-inventorying steps on a process vessel suffered second degree burns when a hydrocarbon release occurred and ignited during preparation for pipe spool removal.
Finding 02
Three Related Incidents at Same Facility in 2015
DCRC experienced three incidents involving process equipment preparation for maintenance in a single year -- August 21, August 28, and November 29, 2015 -- indicating a systemic issue, not an isolated event.
Finding 03
Hydrocarbon Release During Maintenance Preparation
Residual hydrocarbon inventory in the process equipment was released during de-inventorying activities, creating a flammable atmosphere that ignited and burned the operator.
Finding 04
De-inventorying Procedures Were Not Fully Effective
The de-inventorying procedure did not prevent residual hydrocarbon inventory from remaining present in the vessel or piping at the time the operator was exposed to the flammable release.
Finding 05
CSB Issued Safety Bulletin -- No Formal Recommendations
The CSB issued a Safety Bulletin addressing industry-wide lessons on process equipment preparation for maintenance rather than a full investigation report with formal recommendations.
🔍 Root Causes
1
De-inventorying Procedures Allowed Residual Hydrocarbon Presence
The de-inventorying steps performed before the maintenance activity did not ensure all hydrocarbon inventory was safely removed -- residual inventory created a flammable release hazard during the maintenance preparation work.
2
Multiple Similar Incidents Indicated Systemic Procedure Weakness
Three incidents at the same facility within a single year involving equipment preparation for maintenance signal a systemic deficiency in procedures, training, or oversight -- requiring a management system-level corrective response.
3
Maintenance Preparation Activities Carried Unrecognized Flammable Release Risk
Workers and supervisors did not fully recognize the residual flammable material release risk during de-inventorying activities -- a risk that must be systematically addressed by written procedures with step-by-step verification.
☑ CSB Recommendations
→ Industry (Safety Bulletin)
Develop rigorous step-by-step written procedures for de-inventorying and isolating process equipment before maintenance, with verified confirmation steps at each stage that flammable or pressurized material has been safely removed.
→ Industry (Safety Bulletin)
Require supervisor or second-person verification of de-inventorying completion before any process connections are opened or pipe spools are removed from equipment in flammable or toxic service.
→ Industry (Safety Bulletin)
Require atmospheric flammable gas monitoring of the equipment and surrounding area before any maintenance work begins, even after de-inventorying is considered complete.
→ Industry (Safety Bulletin)
Investigate patterns of similar incidents at the same facility as indicators of systemic procedure or training deficiencies requiring management system-level corrective action -- not only per-incident response.
💡 Lessons Learned
Three incidents of the same type at the same facility in a single year are not bad luck -- they are a signal of a systemic deficiency in procedures, training, or supervision. Patterns of similar incidents require a management system-level response, not just per-incident corrective action.
De-inventorying process equipment before maintenance is a critical safeguard step -- but only if the procedure is rigorous, step-by-step, and verified. An assumed or incomplete de-inventorying procedure leaves residual hydrocarbon inventory that workers encounter when they open process connections.
Before any connection is opened on process equipment, an independent second confirmation that de-inventorying is complete should be required. The cost of extra verification is trivially small compared to the consequence of a residual flammable release during maintenance.
Atmospheric flammable gas monitoring should be performed immediately before -- and during -- any maintenance work on process equipment that previously contained flammable materials, regardless of confidence that de-inventorying is complete.
CSB Safety Bulletins communicate actionable lessons to industry even when formal recommendations are not issued. Facilities should review their own procedures against every applicable Safety Bulletin and treat it as a specific prompt for procedure improvement.
SOP: Operating ProceduresMI: Mechanical IntegrityPSSR: Pre-Startup Safety Review
🔨 Safety Meeting Toolbox Talk
►When we prepare process equipment for maintenance, what is the final step confirming the equipment is safe to open? Who verifies that step has been completed correctly and signs off before work begins?
►Has your facility experienced more than one incident involving the same type of work activity? If so, what was done at the management system level -- not just per incident -- to address the pattern?
►Do our maintenance preparation procedures require atmospheric flammable gas monitoring as a mandatory step before opening any process connections?
►When was the last time a supervisor or second person independently verified that de-inventorying or equipment isolation was complete before maintenance began on a high-hazard line?
►How do we translate lessons from CSB Safety Bulletins and other industry incident reports into reviewed and updated procedures at our own site?
Immediate Action Items
✓Review de-inventorying and equipment isolation procedures for process equipment in flammable or toxic service and verify they include step-by-step verification with supervisor sign-off before any connections are opened.
✓Require that atmospheric flammable gas monitoring be performed immediately before the first process connection is opened during any maintenance on equipment that previously contained hydrocarbons.
✓Review your incident tracking system for the past three years and identify any patterns of similar incident types -- especially in maintenance preparation activities -- and initiate management system-level corrective action.
✓Share the CSB Delaware City Safety Bulletin with your maintenance and operations team and compare its lessons directly to your own de-inventorying and equipment preparation procedures.
✓Establish or verify a requirement for second-person verification of equipment isolation and de-inventorying completion as a mandatory step before any high-hazard maintenance activity begins.
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 3 PSM elements (SOP · MI · PSSR). Each represents a documented gap that process safety documentation and consulting can close before a similar event occurs at your facility.

Operating Procedures (SOPs)
Operators cannot reliably hold safe operating limits without clear, current, enforced procedures. Deviation from acceptable operating conditions — a root cause here — is a direct consequence of SOP failure.
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Mechanical Integrity (MI)
Equipment must be designed, inspected, and maintained to operate safely in its intended service. Mechanical integrity failures — degraded equipment, missed inspections, deferred repairs — contributed to loss of containment here.
Supporting documents in our library →
Pre-Startup Safety Review (PSSR)
PSSR is the final checkpoint before hazardous chemicals are introduced into a new or modified system. When PSSR fails or is bypassed, unresolved hazards go live with the process.
Supporting documents in our library →
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