Generator Flex Lead Replacement

Mechanical Dynamics & Analysis (MD&A) experts recently performed a Generator Flex Lead Replacement.  At the customer’s request, the Technical Information Letter (TIL) was completed. MD&A provided all the hardware and replaced all flexible leads.

During the disassembly and replacement of all flexible leads, it was observed that some of the assemblies were too short. The customer arranged for the removal of all asbestos-containing material associated with the flex lead assemblies. This allowed the new flexible leads to be fit and drilled, which created a more uniform bolting configuration with a larger contact surface.

The installation process also involved properly torquing the stainless-steel bolts, distribution plates, and nuts. Textolite barriers were installed over the flexible leads and were secured in place with glass tape. The final assembly was then insulated using fusible rubber tape, with an outer layer of raw glass tape, varnished and then tag painted.

T3 Flex links exposed, found flattened to lengthen

Views of T3’s NEW flex links

Two sets of Generator Stator electrical tests were performed, pre and post flexible lead replacement. The Customer requested that both sets of tests be performed with the unit assembled and under a pressurized carbon dioxide blanket. There were negligible differences between the before and after readings, and all values were consistent with past testing results.

Additionally, MD&A’s experienced team performed on-site testing and inspections of the Generator Stator and Field during a scheduled minor outage, which included visual inspections and a complete series of electrical tests.

A comprehensive visual inspection of the Generator Stator’s Bushing Box revealed a large crack in T3’s Stand Off Insulator (SOI). Once the customer arranged for the removal of the potential asbestos-containing material, the flexible leads, tubular lead, and clamshell were removed, and the old SOI was replaced. The SOI, tubular lead, and clamshell were loosely assembled to ensure proper alignment. All the components were fit checked to be stress-free.

Once all components were verified to be in proper alignment, the SOI and tubular lead were secured in place. The clamshell was blue checked at the HVB (High Voltage Bushing) and tubular lead contact surfaces. Once all component assemblies were verified, the bolting hardware underwent an initial torque. All bolting hardware was torqued a second time, 24 hours later. The assembly was then insulated using fusible rubber tape, with an outer layer of raw glass tape, varnished and then tag painted.

Views of SOI T3 (view of the cracked area)

Views of T3 SOI replacement process

The following series of electrical tests were performed on the Stator while under a pressurized CO2 blanket:

• Winding Copper Resistance
• 5000VDC Insulation Resistance
• DC Leakage
• Hipot
• RTD Resistance and Insulation Resistance Testing
• Flux Probe Resistance Reading
• HIT Skid (Vacuum and Pressure Decay Testing)

A series of electrical tests were also performed on the Field while under a pressurized CO2 blanket, including:

• Winding Copper Resistance
• 500VDC Insulation Resistance
• AC Impedance Testing

All electrical tests were found to be in accordance with OEM Specifications.

Upon completion of the job scope, and a thorough review of inspection observations and test data with the customer, the unit was returned to service.

MD&A is proud to have served the needs of the customer on repair and parts replacement for their generator, providing exceptional quality of workmanship that met their expectations.

MD&A is a full-service OEM alternative for generator service, parts, and repairs with a 35-year track record of successful generator stator and field repairs. We focus on delivering consistent quality and value with fast response, superior communications, and innovative solutions.

Call MD&A today for generator repair and services at +1 (314) 880-3000 or use our Contact form.