Troubleshooting at a Minesite
The usage of ibaPDA-PLC-Xplorer saved many hours of unscheduled downtime and associated production loss
After a scheduled maintenance shutdown in an Ore Processing Plant, the start-up of a particular Sequence came to a grinding halt whenever a certain step in the Sequence was reached. The Plant operators could not determine the root cause of the problem, as their SCADA system was flooded with seemingly unrelated Alarm messages when this Sequence Stop occurred.
A quick initial online monitoring of the S7 PLC logic by the site Engineer also yielded no meaningful clue to the source of the problem.
Quick and easy ad-hoc setup
for any S7 PLC related troubleshooting and optimisation tasks
high speed acquisition
long term continuous as well as trigger/event based
As an iba user, the site Engineer quickly realised that it was time to get serious and to start up their ibaPDA-PLC-Xplorer.Thanks to symbol based S7 program integration, setup of the digital inputs and outputs that required monitoring was a cinch. The
Ethernet based acquisition times was then set to 10ms to get a high resolution capture of the seemingly fleeting event.A short few minutes later, the Plant Operators were asked to attempt another Sequence start. As soon as the Sequence crash occurred, the Engineer took one look at the live data on his ibaPDA trend screen and immediately realised the root cause of the problem. The trend clearly showed that all previously active 24V digital inputs dropped to zero a mere 150ms after the Sequence program gave the command to activate a particular digital output.
This “loss” of all the 24V digital inputs led to the Alarm flooding on the SCADA system as well as the PLC program immediately aborting the Sequence. Since this sequence stops also led to a deactivation of any associated digital outputs (including the one that “drained” the 24V supply), all inputs became healthy again some 50ms later. As all of this happened in the blink of eye, it was impossible to observe it via traditional SCADA or S7 PLC online monitoring means.
Based on the ibaPDA captured data though, the root cause was obvious and fixed a short time afterwards. As it turns the digital output in question activated a Solenoid valve which had been immersed in water during maintenance work. This now created a partial short circuit which drained the 24V supply.
All up, the identification of this rather simple problem was made possible by the power of ibaPDA-PLC-Xplorer capability for high speed Ethernet based data acquisition, trending and analysis capability.