Background
The Quad Plus team was called out to this aluminum mill to perform scheduled preventive maintenance of their protection power equipment. The mill purchases mostly recycled materials from various suppliers to produce coils of aluminum alloys that are then sold to their customers who produce automobiles, cans, building materials, and more.
During the execution of the preventive maintenance service, the team discovered a defective electrical mechanical relay on the B-phase of their hot mill stand protection scheme. The relay would not trip the circuit breaker if a fault as on the B-phase. The failure to trip could lead to catastrophic equipment failure or injury to personnel.