An unexpected explosion occurred within a storage tank at a U.S. petrochemical manufacturing facility, producing a forceful overpressure wave that rattled nearby buildings and released a large black cloud of smoke. In the aftermath, the facility owner launched a formal investigation to determine the underlying cause and to reconstruct the conditions that existed inside the tank immediately before the event.
A key uncertainty in the investigation was the composition of the vapor mixture inside the one-million-gallon storage tank. Understanding whether the mixture could have entered a flammable regime required a rigorous evaluation of how temperature, oxygen concentration, and nitrogen dilution influence flammability limits.
Our partner ioKinetic was engaged to analyze the flammability behavior of the materials involved and identify root causes. The team developed detailed flammability triangles for the flammable chemical stored in the tank, along with nitrogen and oxygen, across a range of temperatures. This allowed an evaluation of how flammability limits shift as temperature, oxygen concentration, and nitrogen dilution change — key factors in understanding whether the mixture inside the tank could have entered a flammable regime.
Their methodology followed the framework outlined in “A Detailed Method for Estimating Mixture Flammability Limits Using Chemical Equilibrium” by Georges Melhem, Ph.D., FAIChE. Leveraging this approach, ioKinetic applied its extensive experience in flammability analysis, incident investigation, Root Cause Analysis, verification of physical evidence, and structural assessment to generate accurate and defensible results.
Comparison of air and oxygen (as oxidant) confirms consistent flame temperatures on the LFL and wider ULF, as anticipated.
Identifying root causes is an important part of any incident investigation. The flammability characterization provided by ioKinetic became a pivotal element of the client’s investigation. By identifying the range of mixture compositions that could have existed inside the tank, the client gained a clearer understanding of the conditions that may have led to ignition and explosion. This insight strengthened the technical foundation of the root cause analysis and supported informed decision‑making regarding corrective actions and future risk mitigation.