*Michael Economides, a University of Houston chemical engineering professor familiar with the refining process, said that when a raffinate splitter is taken out of service for maintenance all flammable substances should be removed.
Liquid is drained, he said, and vapor is purged from the system with a blast of inert gas.
"These high-end hydrocarbons are not just flammable," he said, "they are eminently explosive ... This is big, intricate equipment with many nooks and crannies, and it is conceivable that there could have been a pocket of gas still somewhere in the unit."
Gas left in the system could be touched off by a welder's torch, or virtually any other source of ignition, with catastrophic results."*