During the 2023 shutdown outrigger 1 failed. While performing the HE Probe removal we found that the outrigger could only travel vertically about one inch in each direction.

Upon further inspection we found that the linear bearings had been pulled off the ball screws. And 2/3 of the ball screws had been bent. Additionally one of the linear bearings broke and was missing some of the balls, the parts were later found inside the tank.

The event that caused the failure is unknown, but one guess is that while the outrigger was in the home position the shoulder joint was opened before the elbow joint.

The outrigger was repaired on March 21st, using parts from the old outrigger. After the shutdown the parts should be replaced again with new parts. Additionally it was observed that the linear bearings are quite old so they should be replaced on outrigger 2 also.  See photo for details on which parts where repairs or replaced.

Update 2023-09-01: Both outrigger 1 and 2 had the linear bearings replaced with brand new bearings. Note that the same brand and part number was used (Thomson super-12-OPN ball bushing), however the quality of the new ones seems to have decreased and likely will not last as long as the previous ones. It is recommended that we review if they need to be replaced again in 5-10 years.