A Monday before a recent 4-day holiday weekend, Bearing Headquarters received a call from a utilities company with a unit down because the 10” diameter output shaft on the main gearbox twisted off. After some conversation with our reducer rebuild shops, the customer shipped the gearbox and the bull gear being driven by the gearbox repair shop in Keokuk, Iowa. The reason for shipping the driven bull gear assembly was to do an overhaul on the gearbox and check the integrity of the entire assembly.
The 18,000 lbs. gearbox and 21,000 lbs. bull gear assembly arrived in Keokuk, Iowa on Tuesday morning. The gearbox was completely stripped down and the housing was thoroughly cleaned and inspected using our Faro arm (laser measuring device) to check the concentricity of the bores and the parallelism of the bores in a shaft line. All of the gears were removed from the shafts; the gears and the shafts were tested using Magnetic Particle Testing (Magnaflux Test). The same was done to the large bull gear assembly, the shaft was stripped and the gear was removed. After the Magnaflux inspection, a crack was found in the intermediate gear of the gearbox and a crack was found on both of the bearing adapter plates on the bull gear assembly. The gear was modified for a temporary fix and new adapter plates were made.
All the bearings and seals were replaced in the gearbox and on the bull gear assembly, a new 10” diameter output shaft was made for the gearbox, the intermediate shaft of the gearbox was modified, new bearing adapter plates were made for the bull gear assembly, the bull gear assembly was reassembled, and all the bearing end plays were set to tolerance.
After only having the box and bull gear assembly for less than 2 weeks and over a long holiday weekend, the repair was returned to the customer to meet their very fast turnaround. The customer installed the gearbox and bull gear within days and the unit is running smoothly.
All of the gears were printed while the gearbox was being repaired to offer the customer spare gears for a quick turnaround if the gearbox starts to show signs of trouble.
Faro Arm Video:
Magnaflux Testing Explanation: