Explosion of a Cooling Tower Dosing System

An explosion occurred involving a chemical dosing system for cooling tower water at an industrial facility. Fragments of the dosing system equipment were ejected, causing fatal injuries to the water treatment operator. This was an unusual and unexpected incident for a water treatment system. The system had no automation, data recording, or other means of recording the operator’s actions or the process parameters leading up to the incident. This paper will discuss the scientific investigation that gathered the physical and chemical facts, apply a fault tree analysis, and conclusively determine the direct causes of the explosion. The dosing system was designed to, among other treatments, provide a biocide at low levels into the cooling water system to control microbiological growth and fouling. The facility had changed biocide chemicals years prior to this, and leftover drums of a prior biocide had recently been found. The treatment operator made a decision to pump the old biocide into the chemical dosing loop. The investigation determined the sequence of decisions and actions leading up to the explosion. The root causes included inadequate management of change, hazard analysis, and chemical compatibility assessment. This paper will summarize the analysis of these aspects and provide lessons learned.