Signal jump causes interlock trip
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1. The 15# CO2 compression unit in our company uses a TRICON system; on May 31, 2018, the unit stopped operating due to an interlock being triggered by the loss of signal from the emergency stop button on site. As can be seen from the diagram, the signal of the on-site parking button d271HS_1003 changes from false to true within just one scanning cycle. Upon checking the surveillance footage, no one was present at the site, so human error is ruled out. 2. On June 12, 2018, the gasification Unit B of our company triggered a major interlock due to the loss of the signal indicating that the valve 17XV2207 was in the open position, resulting in the shutdown of Unit B. An on-site inspection of the valves and signal wires revealed no abnormalities. The phenomena associated with these two events are very similar. Our company has analyzed them on many occasions, but we still cannot determine the exact cause I earnestly ask my colleagues to help analyze where exactly the problem lies. How to prevent such incidents from occurring in the future. If the cause cannot be found, such incidents may occur again; there’s really nothing that can be done! Thank you all here first!
Looking at the SOE records, HS1003 was maintained for only 100ms. If the wire is not loose, the probability of malfunction caused by interference is high.
Poor contact, interference, malfunction, and delays.
It’s better to first assess the extent to which adding a delay will affect the system’s processes. If a delay is not possible, it is still necessary to check the wiring to see if there are any sources of interference such as high voltage or high frequencies along the cable path between these two points
There is a high possibility of interference or poor contact; check the system logs again to see if there are any issues with communication (300ms seems to be a scanning cycle) or with the hardware. If that doesn’t work, consider replacing the emergency stop switch contacts with ones that have detection functions for open circuits/short circuits, or try using isolators with those contacts.
The suggestion upstairs is good; if the manufacturing constraints permit, considering adding a delay would be advisable. Faulty operation of the emergency stop button and valve feedback can be resolved by replacement. It is also necessary to check and confirm whether the wire connections are oxidized, poorly connected, or loose due to vibration.
There are many factors at play; could it be that the temperature between the cabinets is too high? Could it be that the vibration of the equipment itself at the site has caused the connections to loosen? Could it be interference caused by magnetic field fluctuations from electric welding or similar activities in the vicinity? ···
It could be due to signal interference; of course, component aging is also a possibility. The cause is usually hard to determine as there is no pattern to it. Solution: Delaying the operation is a good approach, but the process requirements need to be taken into account. Generally, the delay ranges from a few seconds to several dozen seconds, and this is determined based on practical considerations
It can be seen that it returned to normal after 100ms?
It happened to us before; it was because the wire came loose.