Read about interesting installations, unique engineering solutions, or quick turnaround times for emergency repairs in our portfolio of nuclear motor repair case studies. Check back frequently to get our most recent updates on our newest projects and learn how we solved our customer’s most difficult and demanding problems.
Unique Nuclear Motor Repair Solution Saves Power Plant Hundreds of Thousands of Dollars
A critical nuclear power plant in Northeastern U.S. experienced a failure during routine operational testing of a safety-related EQ motor that drives a fan in the containment fan cooling unit. The nuclear power generating facility that experienced the problem is a two-unit pressurized water reactor (PWR) that provides electricity to over two million homes in the region. The damaged nuclear motor prompted immediate action by the plant as the fan that the EQ motor was running provided the critical safety function of emergency cooling during loss of coolant accidents (LOCA) or main steamline breaks (MSLB).
Power plant technicians contacted the Schulz Electric nuclear group due to their extensive expertise with EQ insulation systems and their ability to provide emergency repair services for safety-related motors. As a stop gap measure, Schulz Electric reconfigured the plant’s spare EQ motor overnight by performing an F1 to F2 conversion. The plant installed the spare nuclear motor and sent the failed electric motor to the Schulz Electric facility for failure analysis and repair. During Schulz Electric’s failure analysis, experts found that the EQ electric motor was experiencing a decreasing air gap caused by cracked stator frame welds, which eventually led to stator-to-rotor contact and a subsequent trip on overcurrent during startup. The damaged welds caused the stator to become partially disconnected from the frame cage and flex inwards during motor startup where the nuclear motor is subjected to the most severe electro-magnetic forces.
After evaluation, the Schulz Electric team proposed a motor rewind utilizing their own fully qualified form-wound continuous-duty EQ insulation system, as well as a stator cage redesign and upgrade. “As an expert in nuclear motor repair, we try to not only fix problems but determine the root cause of the failure and offer solutions that can eliminate the failure mode,” said Whit Ward, a field support engineer for Schulz Electric. “The cage redesign for the nuclear motor was unique. It had to fit in the existing frame and house the existing stator core. Our engineers designed the cage to maximize the base metal contact at the welded joints, which eliminated the failure mode by distributing the electro-mechanical stresses that caused the welds to fail. So essentially what we did, was engineer out the defect in the critical EQ motor,” finished Whit.
The stator cage was designed to meet the plant’s seismic qualification criteria. This was verified through an extensive seismic qualification and complete structural analysis of the equipment. Despite a short turnaround time, Schulz Electric was able to deliver the repaired nuclear motor and save the plant thousands of dollars and months of waiting they would’ve experienced if they were forced to buy a new OEM replacement. “We’re proud of what our team was able to accomplish under such a short timeline,” said Amara Griswold, engineering manager from Schulz Electric. “After working closely with the plant, we were not only able to save them thousands of dollars and months of downtime, but we were able to deliver a far superior upgrade that removed the known failure mode and increased the overall reliability for this critical safety-related equipment.” The customer was so pleased with the final result that Schulz Electric became the plant’s preferred vendor and subsequently repaired four more nuclear motors that were experiencing the same deficiencies, thereby saving the facility hundreds of thousands of dollars.
Schulz Electric’s nuclear group specializes in nuclear motor repair. We offer a variety of nuclear services including environmentally qualified form and random wound insulation, contaminated electric motor repair with RCP electric motor overhaul and rewind, safety-related repairs, electric motor testing capabilities, high quality, cost effective solutions for MOV dilemmas, all from our nuclear motor repair facility and in-house decontamination facility.