Collector Ring Repair Upgrades Steel Plant Equipment and Restores Operations

Smith Services deployed the field service team to the customer site, and the electric motor and control systems were inspected to determine the cause of the failure. They identified the problem as an electrical failure at the collector rings (also known as slip rings). Contamination of the laminate material used for insulation on the collector rings and a faulty contact on the field discharge resistor in the electric motor control system were the causes of the problem. The field discharge resistor failed due to a high voltage spike in the rotor circuit. This, combined with laminate material contamination, caused the collector rings to fail ultimately.

“Most electric motor repair companies would just fix what failed and return the motor to OEM condition,” said Adam Watts, engineering manager for Smith Services. “At Smith Services, we take it a step further (whenever possible) and pride ourselves in performing failure analysis. We not only repair electric motors quickly, but we also present customers with innovative solutions. Leveraging the latest technologies, insulation systems, and manufacturing techniques, we engineer long-term and reliable solutions so customers can get the most out of their equipment,” said Adam.

And in the case of the equipment failure for the steel plant, doing an upgrade for the customer was no exception. In addition to repairing the control system components, Smith Services offered the customer a collector ring upgrade featuring an innovative split-ring configuration that allowed for easier, in-place maintenance and replacement without having to remove the equipment from service.

The new collector ring design featured non-porous, chemical-resistant insulation material with increased dielectric strength to combat particulate contamination. Additionally, the new system included a spark-gap safety that provided a method to effectively dissipate the energy generated in the field circuit during motor start-ups should the field discharge resistor fail in the future.

After evaluating Smith Services’ proposal, the customer elected to perform the repair and upgrade on the large generator. The large motor-generator set repair was completed on-time and remained in service, running flawlessly for six years until the next scheduled routine bearing maintenance (which typically includes a collector ring replacement). During routine maintenance, they found that the upgraded collector rings installed six years earlier were still in good condition, did not need replacing, and were fit for continued service.