This morning during routine service bridge work in the Cyclotron tank, it was observed by Travis Cave that the cable tray for the Remote Handling service bridge was catching on something on the top inside surface of the Cyclotron tank. The cable tray was observed to visibly snag on this protrusion and then bounce around.
Isaac Earle and Grant Minor conducted an inspection from the edge of the Cyclotron tank with cameras and binoculars. The contact point was identified and photos and video were recorded (see attached).
After a meeting with Yuri Bylinski it was identified that the item interfering with the cable tray was a beam scraper foil (part of the Resinator D Gap), close to the center post area.
A number of causes for the snag were suspected:
- The upper tank lid might not have been at its upper limit (i.e. not raised completely by the elevation jacking system)
- The center post bearing for the service bridge might not be seated properly
- The cable tray mounting bracketry or air cylinder may have been displaced
After inspections of the service bridge before and after removal from the tank, it was determined that neither 2 nor 3 were the cause of the problem.
It was observed by the Remote Handling group that the upper limit switches located at stations 1 and 10 had not advanced high enough to mechanically "click", even though their wheels were contacting the reference surface. There was about 0.5 to 0.75 inch of travel remaining in these switches (see attached photos) before clicking.
It was also observed that the wooden stick normally set flush with the Cyclotron roof beams at max height was about 0.5" below the roof beams (measured with a Starrett scale by Grant Minor).
After further assessment, it was also determined by Dan Louie and Yuri Bylinski that the limit switch lamp on the elevating control system was actually not lit, even though it appeared so. The dull glow in the lamp was due to the neon style of the bulb, which can glow a small amount even at very low voltages and appear to be lit. A test of raising the switches while watching the lamp revealed that the lamp switched on brighter after the limit clicked.
The upper tank lid was raised around 6pm by Dale N. with Yuri Bylinski and Grant Minor present. The stick advanced upwards about 0.5" almost completely to the ceiling (see attached photos).
Until a systematic method of measurement of the vertical displacement of the system is developed (this may be the purpose of the dial indicators at each station, but requires further investigation), this problem can be avoided again by always checking both the limit switches and the distance from the calibrated "wooden stick" to the cyclotron roof beams. |