| ID |
Date |
Author |
Category |
Type |
Subject |
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42
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Tuesday, November 19, 2019, 10:31 |
Adam Newsome | T-Hall Crane | Repair | 900VFD Encoder Board Replacement | An issue arose in which the ARIEL crane hoist could not be moved. It was determined that the East and West drums were out of synchronization (by more than 0.2 m, which the limit) and the encoder board inside the 900VFD had failed.
Summary: The synchronization and encoder board issues were resolved, and the crane is now functional. The root cause of both of these issues is unknown.
The following is a timeline of events for record, in case a similar issue arises again:
Nov 6:
- Crane hoist not working
- Contact was made to COH to initiate troubleshooting
- Faults were observed: Drive fault for 700VFD, Drive fault for 900VFD and 900VFD not ready, Main Hoist Drum East and West Absolute Encoders Position Difference
- Logging in to the HMI as a maintenance user and viewing hoist feedback showed that: East drum absolute and incremental encoders agree with each other, West drum absolute and incremental encoders agree with each other, West drum and East drum encoder values do NOT agree with each other (approx 0.22 m difference, the threshold for faulting is 0.2 m)
Nov 12:
- Crane hoist mode was switched to operate only the East drum independently, and adjust it so that the encoder readout on the HMI of the difference between East and West drums was approximately 0... the red X indicators changed to a green checkmark, and the encoder difference fault was eliminated
- An attempt was made to operate both drums simultaneously again, but the drive faults persisted... contact was made to COH for further troubleshooting
- Hugo from COH suggested moving the encoder board within the VFD from 900VFD to 700VFD, to see if the "drive not ready" fault followed the board, to narrow down the issue. This swap was made, and it was determined that the issue was in fact due to a faulty encoder board. The VFD itself displayed fault code 4030 (Enc 1 open wire). A replacement as well as a spare were ordered (Allen Bradley 20-750-DENC-1).
Nov 18:
- The encoder board within 700VFD was replaced with a new one (this is the one that was previously in 900VFD)
- The fault messages were eliminated, and both drums could be run independently and simultaneously
Nov 19:
- Thomas Kauss, Travis Cave, and Adam Newsome tested the crane to verify functionality and check for synchronization of drums
- The drums are synchronized, as described in the operator's manual (visual verification of tick marks on hoists, 17 turns of rope when at upper limit)
- The crane was run to its upper limit and down a few times, and the hoists were observed: nothing out of the ordinary was noted |
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Friday, November 29, 2024, 15:23 |
Adam Newsome | Hot Cell 1 | Maintenance | 1000 kg crane: y axis position display not functioning | After a recent power cycle, the y-axis referencing was lost for the 1000 kg crane. The position readout was also incorrect, somewhere on the order of > 30,000 mm. On 2024-11-29, A. Newsome re-referenced the y-axis. The position readout correctly reset to zero, and both +y and -y motion is functioning correctly, but the y-axis position readout on the HMI constantly displays 0 and does not change. To be investigated.
Update 2024-12-02:
After going online with the PLC, it was determined that the reason for the display of 0 as the position is that the two values used for calibration of the +y and -y limits were actually the same, meaning the scaling factor (the difference between these two values) was 0, which resulted in the displayed value being 0. The root cause of this is that the encoder was not functioning correctly so its value was not changing when the crane moved and it was stuck at one value. Upon investigation of the encoder input card, the red "ERR" light was on. This indicates the encoder signals are not properly reaching the input card. Once this was discovered, it was remembered that this happened in July 2024 as well (no e-log was written). In July, the root cause was identified as being a loose encoder signal wire in a junction box. Junction box CJB1-BC, located on the bridge crane near its disconnects, was opened and investigated. Upon checking each wire, it was determined that the red wire seemed not to be making full contact. The wire was removed and re-inserted, and the "ERR" indicator on the encoder card turned off. The crane's +y and -y limits were re-referenced. The crane is functioning normally after re-referencing. (Note: if something like this happens again, during the re-referencing process, the displayed value on the HMI will be incorrect.. this is because the PLC's scaling factor is not fully adjusted until both +y and -y limits are reached. The actual encoder measurement taken at those limits is used for the scaling factor. This is not an ideal way to program the system, but this is how it works with all ARIEL hot cell subsystems. So incorrectly displayed values can be ignored, in general, until full referencing is completed). |
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