Herrig Brothers Farm Propane BLEVE | SafeGuard PSM Case Study

📋 Incident Summary

On April 9, 1998, a propane boiling liquid expanding vapor explosion (BLEVE) at the Herrig Brothers Farm in Albert City, Iowa killed two volunteer firefighters and injured seven others. An all-terrain vehicle (ATV) had struck and damaged the piping connected to a 30,000-gallon propane storage tank on the farm property, releasing liquid propane that ignited and began burning. When the volunteer fire department arrived to fight the fire, the burning propane tank catastrophically failed — a BLEVE — launching tank fragments and a fireball that killed the two firefighters.

The ATV had struck a propane fill pipe connected to the large storage tank, shearing the pipe and initiating the propane release and fire. The fill pipe lacked an excess flow valve or other automatic shutoff that would have stopped the propane flow when the pipe was sheared. The volunteer firefighters who responded were not adequately trained on the behavior of propane BLEVEs or the standoff distance required to survive a propane tank BLEVE event.

The CSB investigation found that the absence of an excess flow valve on the propane fill pipe was the primary enabling factor for the sustained propane release. In addition, the local volunteer fire department lacked training specific to propane BLEVE hazards and did not maintain the standoff distance that would have protected firefighters from the tank failure. The case underscores the importance of both mechanical safeguards on propane systems and emergency responder training on BLEVE behavior.

🔎 Key Findings

Finding 1

ATV Struck Fill Pipe, Shearing It and Releasing Propane

An all-terrain vehicle struck the fill pipe connected to the large propane storage tank, shearing the pipe and initiating a sustained release of liquid propane that ignited.

Finding 2

No Excess Flow Valve on Fill Pipe

The sheared fill pipe had no excess flow valve or automatic shutoff that would have stopped propane flow when the pipe was damaged. An excess flow valve is a fundamental safeguard against piping failure-caused propane releases.

Finding 3

Propane Fire Exposed Tank to Heat, Causing BLEVE

The sustained propane fire heated the tank shell above the liquid propane level, weakening the steel and ultimately causing a boiling liquid expanding vapor explosion — one of the most dangerous failure modes of a pressurized vessel.

Finding 4

Firefighters Not Trained on BLEVE Standoff Distance

The volunteer firefighters who responded were not trained on propane BLEVE behavior or the safe standoff distance required to survive a propane storage tank BLEVE. They were within the lethal fragment range when the BLEVE occurred.

Finding 5

Two Volunteer Firefighters Killed by BLEVE Fragments

Tank fragments and the fireball from the propane BLEVE killed two volunteer firefighters who had approached the burning tank without knowledge of the lethal radius of a propane BLEVE.

Finding 6

BLEVE Radius Significantly Underestimated by Responders

The responding firefighters did not have specific knowledge of the propane BLEVE lethal zone, which can extend hundreds of feet from a large propane storage tank.

🔍 Root Causes

Absence of Excess Flow Valve on Fill Pipe

The primary enabling factor was the absence of an excess flow valve on the propane fill pipe. An excess flow valve would have automatically stopped propane flow when the pipe was sheared, preventing the sustained release and fire.

Inadequate Emergency Responder Training on BLEVE Hazards

The volunteer firefighters did not have training on propane BLEVE behavior, recognition of pre-BLEVE warning signs, or the standoff distance required to survive a BLEVE from a large propane storage tank.

ATV Operating Near Propane Storage Piping

The ATV was operating in proximity to propane storage piping without protective measures to prevent vehicle impact with the fill pipe or other exposed connections.

☑ CSB Recommendations

→ Propane Industry / NFPA

Require excess flow valves on all propane fill lines connected to large agricultural and commercial propane storage tanks to prevent sustained release when piping is damaged.

→ Fire Service / State Fire Marshals

Develop and distribute BLEVE hazard training for volunteer fire departments, specifically covering propane tank BLEVE recognition signs, lethal fragment radius, and minimum standoff distances.

→ Iowa State Fire Marshal

Require all local fire departments responding to propane fires to maintain minimum standoff distances based on propane tank size until the fire is safely contained or the tank is confirmed cooled below BLEVE temperature.

→ Agricultural Propane Industry

Implement vehicle impact protection for propane fill pipes and other vulnerable piping connections at large agricultural propane storage installations.

💡 Lessons Learned

⚠ Excess flow valves on propane piping are passive, automatic safeguards that stop a catastrophic release when piping is damaged. They are inexpensive, reliable, and required by code in many applications — but their absence converts a pipe strike into a mass casualty event.

⚠ A BLEVE is one of the most dangerous failure modes in emergency response. Firefighters who approach a burning propane tank without BLEVE training do not know they are within the lethal fragment radius until it is too late.

⚠ Emergency responder training on propane BLEVE behavior — recognition signs (tank discoloration, flame impingement, pressure relief valve cycling) and standoff distances — is a life-safety training requirement for any jurisdiction with propane storage.

⚠ Vehicle impact protection for exposed propane piping on farms and commercial facilities is simple and inexpensive. An ATV guard rail or bollard that prevents pipe shearing can prevent the ignition event that precedes a BLEVE.

⚠ When propane tanks are on fire, cooling the tank to prevent BLEVE is a valid emergency response strategy — but only when responders maintain adequate standoff distance and have sufficient water supply to accomplish it safely.

PSM Elements: PSI · EP · SOP · TRN

🔨 Safety Meeting Toolbox Talk

Topic: Propane BLEVE Hazards & Emergency Responder Safety

💬Do all propane fill lines at our facility have excess flow valves that will automatically stop propane flow if the pipe is sheared or significantly damaged?

💬Are all exposed propane piping connections at our facility protected from vehicle impact by bollards, guard rails, or other physical barriers?

💬Do our emergency response procedures for propane tank fires include specific standoff distances based on tank size, and are first responders trained on BLEVE recognition and standoff distance requirements?

💬Are local fire departments and emergency responders who would respond to a propane emergency at our facility trained on BLEVE behavior and minimum safe standoff distances?

💬Do we conduct periodic coordination with local emergency responders to review our propane storage volumes, fire response procedures, and the specific BLEVE hazards at our facility?

✎ Team Action Items

✓Identify all propane fill lines and exposed piping connections at your facility — verify excess flow valves are installed and have been tested within the manufacturer recommended interval

✓Walk around your propane storage area and identify any exposed piping connections that could be struck by vehicles, forklifts, or other mobile equipment — verify adequate impact protection is in place

✓Pull your emergency response plan for a propane storage tank fire — verify it includes specific standoff distances based on your largest tank size and BLEVE recognition criteria

✓Contact your local fire department and verify they have received BLEVE hazard training relevant to the propane tank sizes at your facility

🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 4 PSM elements (PSI · EP · SOP · TRN). Each represents a documented gap that process safety documentation and consulting can close before a similar event occurs at your facility.

Process Safety Information (PSI)

Accurate, complete Process Safety Information is the foundation every other PSM element depends on. When PSI is missing or wrong — chemistry data, equipment specs, P&IDs — the entire hazard analysis is built on a flawed base.

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Employee Participation

OSHA PSM requires workers to be meaningfully involved in hazard analyses and procedure development — not just trained on the finished product. Active participation catches gaps that management alone misses.

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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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Training & Operator Competency

Workers must understand process hazards — not just the steps on the page. Training records, refresher frequency, and verified competency are all OSHA PSM requirements that gaps here violated.

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