Investigation: How dust exploded during railcar loading
When a dust explosion occurs, it can injure workers and damage your equipment. This article explains how a safety consulting firm ran tests to determine what caused a dust explosion in a railcar during gravity loading of a powder. The final section lists the firm's suggestions for preventing another dust explosion in the loading operation.
For some time, a railcar loading operation at a chemical manufacturing plant worked smoothly. In the operation, a fine chemical powder discharged from a dryer was loaded by gravity from a holding hopper into a railcar. The powder contained some residual solvent. The holding hopper was electrically grounded and had an inert nitrogen gas atmosphere. A rotary valve at the hopper outlet controlled the powder feedrate to the railcar. Powder traveled through a steel pipe below the rotary valve, through a flexible hose with double walls [sometimes called elephant trunking] that sandwiched a metal reinforcing wire, and into the railcar. Inside the railcar, compartment walls had a relatively thick sanitary coating to prevent rust on the walls from contaminating the powder.