In an automobile paint plant, a technician left his workstation at 4:15 pm in forgetting to turn off the pump used to transfer paint containing 55% acrylic resin, 15% xylene, 16% butyl acetate and 4% ethylbenzene. The transfer of resin from one diluting tank to another began at 3 pm and ended after 5 pm, as programmed, but the pump kept running. Given that its safety shutoff (tripped by an insufficient flow rate) was inoperable, the pump ran with no load for 11 hours, causing gradual heating of the resin inside the pump core along with vaporization of the solvent, which wound up rising to the level of the diluting tank. The plant watchman, who had seen the smoke and noticed smells emanating from the building’s 1st floor, sounded the alarm at 2:30 am in contacting the on-call plant employee and then calling fire-fighters. These first responders arrived at 2:55 am and proceeded by isolating the pump and monitoring it until all fumes had disappeared. The on-call person and responders left the scene at 4:40 am. Upon resuming activities two days hence (Monday), the pump’s thermal protection short-circuited; maintenance personnel observed that the pump had been blocked due to resin build-up.
The manual pump shutoff procedure during unscheduled operations was not respected. Extended pump operations with no load heated the resin left in the pump core, causing the resin to melt. Upon cooling, this resin mass solidified and prevented the pump from running.
Subsequent to this incident, the pump shutoff safety system was modified. An exceptional procedure, including a dual control, was implemented while awaiting safety system modification and improvement. Moreover, it was planned to create a dedicated acrylic resin distribution network from the storage facility to the diluting tank without requiring holding in an intermediate tank.