A professional who operates or controls stills, compressors, reactors, and related chemical process equipment during rest periods, lunch hour, or emergency, performing duties of regular operators as directed by operators or supervisory personnel.

• When not relieving equipment operator, performs tasks such as assisting operator in turning valves to control flow of materials, setting equipment controls at specified readings, gauging tank levels, and recharging equipment with fresh catalytic agents.
• May be designated according to equipment operated or worker relieved as benzene-still utility operator; butadiene-converter utility operator; dehydrogenation-converter utility operator; ethylbenzene-compressor utility operator; styrene-continuous-still utility operator.