An employee for a mechanical contractor was working at a large automotive plant in southeast Michigan. His supervisor decided that an air vent was not sitting correclty on top of an 18 inch grooved 90. The supervisor instructed the employee to loosen the bolts on the coupling holding the 90 to the straight run of pipe. The system was currently under a 150 lb. air test. Upon loosening the nut on the coupling the fitting exploded apart and shot an air column through the roof of the automotive facility. The employee was not injured; however, the damage to the roof exceeded $100,000. This maneuver almost cost much more than the price of a new roof.
