Hello, I am currently facing a recurring issue that I am struggling to resolve. Our setup includes a line with 3 thermocouple input cards (1756-IRT8I) installed on a remote rack. The diagnostic bits indicating whether the thermocouple inputs are faulted serve as permissives for the line to operate. Periodically, the line shuts down, and our historian data shows that this is due to the fault bits being triggered. Interestingly, it is not every bit every time; rather, it appears to be all fault bits on a single card during each occurrence, suggesting a loss of communication between the cards and the PLC. This communication loss lasts for only 1-3 seconds. I have already attempted replacing the Ethernet connections and the switch between the remote and main racks, but the issue persists. Has anyone encountered a similar situation before? The rotating occurrence of faults on different cards each time leads me to suspect a potential issue within the remote rack itself, although the exact cause remains uncertain. While it is unlikely that all 3 TC cards are failing simultaneously, it is a possibility worth considering. Thank you for any insights or advice you may have.
Are you monitoring the status of the ENxT module utilized for communication with the rack? Have you examined the port diagnostics for the Ethernet module? Is it set up in a Ring or Star configuration? What firmware version is running on the Ethernet module? Have you investigated potential power fluctuations affecting the rack's power supply? In the interim, consider setting denounce timers for the fault condition. If the system automatically recovers in 3 seconds, most processes should be able to withstand a brief temperature loss.
Hey there, I've had a somewhat similar issue before. As you've replaced Ethernet connections and the switch, and the issue still persists, maybe the problem lies within the cards or the slot on the rack. You may want to check if the ControlLogix chassis backplane or the I/O module itself is faulty. Try swapping the suspected faulty card with a card from another slot. If the issue moves with the card, it's probably the module. Should it stay with the slot, you're likely looking at a backplane or remote rack issue. Also, keep an eye on the rack environmental conditions. Extreme temperature changes or vibrations could also have an impact on the function of your cards. Lastly, consider checking your cabling quality, the grounding, or there could be some electromagnetic interference.
I'd be inclined to agree with your suspicion that the issue lies within the remote rack itself, given the rotating nature of the faults on different cards. This could indeed suggest an internal communication issue within the rack. Considering the short duration of the communication loss, it might well be a power supply issue. Have you checked the power supply to the rack or considered replacing it? Also, ensure the firmware versions of your PLC and the thermocouple input cards are compatible. If the parameters are not aligned, they might cause intermittent faults. It might be worth doing a firmware upgrade if there have been any recent releases. In the end, if none of these solutions work, you may want to try swapping out the remote rack itself.
I have encountered a similar issue in the past. It turned out to be a synchronization problem within the remote rack, particularly with how it handles time-critical information. An intermittent loss of communication, as brief as it may be, can trigger false faults due to the skew in timestamps. You may want to validate the firmware version of your 1756-IRT8I input cards and update them if necessary. Indeed, it's less likely that all 3 TC cards are failing simultaneously, but it wouldn't hurt to check their individual operative conditions. If feasible, perhaps run a test using substitute cards and see if the issue persists. These steps might help narrow down the causes.
It sounds like you’re in a tricky situation! Given that the issue seems to be intermittent communication loss, it might be worth checking the power supply conditions to the remote rack. Fluctuations in power can sometimes cause temporary communication drops. Additionally, consider looking into the network configuration settings, like multicast settings or any potential broadcast storms that could be influencing stability. It could also help to monitor the error logs on your PLC for any network-related messages during the shutdowns; they might provide more insight into the root cause. Good luck, and I hope you can get it sorted soon!
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Answer: Answer: The intermittent faults could be due to a loss of communication between the thermocouple input cards and the PLC, lasting for 1-3 seconds, leading to the fault bits being triggered.
Answer: Answer: To troubleshoot communication loss, you may consider checking the Ethernet connections, the switch between the remote and main racks, and inspecting the remote rack for potential issues causing the intermittent faults.
Answer: Answer: The rotating occurrence of faults on different cards each time suggests a potential issue within the remote rack. However, it is also worth considering the possibility of individual thermocouple input cards failing simultaneously. Further diagnostics may be needed to pinpoint the exact cause.
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