C
We have SLC 500/05 plc (Allen bradly) here at site. it is found that the asb (ASB 1794) on the rack 3 is declaring local fault with out any provocation.
rack 3 is the last rack and we have 6 analog input cards and 2 analog output cards (respectively) on that rack. we have tried our best to remove that fault but still that fault is popping up.
a few days prior to the commissioning (May 2014) of the plant it started showing "local fault". very first times the local fault indication was blinking. and then it started flickering. when it starts blinking, the status indication on analog cards (7th and 8th slots) starts blinking. and gives weird and random signals on the every channels on the cards and the signals on the 6th card (analog input) won't be read out. and give random values on the SCADA.
remaining 5 analog input cards don't show any problem at all.
the plant ran smoothly for 1-2 weeks. after that we took a shut down and now all of a sudden it declared local fault. the point is that we took a shut down and all the instruments and motors are not on line.
we have put resistors on the scanner and the ASB of the last rack (150 ohms each). the dip switch on the ASB is checked and the baud rate is selected to 57.8.
just to confirm that the chassis and the cards are not faulty, we changed the chassis and cards of slot 6 and 7. still this same problem popped up.
only on rack 3 we face this issue.
what could be the reason of the local fault declaration? how could i get rid of this? can anyone please help me out to resolve this issue?
rack 3 is the last rack and we have 6 analog input cards and 2 analog output cards (respectively) on that rack. we have tried our best to remove that fault but still that fault is popping up.
a few days prior to the commissioning (May 2014) of the plant it started showing "local fault". very first times the local fault indication was blinking. and then it started flickering. when it starts blinking, the status indication on analog cards (7th and 8th slots) starts blinking. and gives weird and random signals on the every channels on the cards and the signals on the 6th card (analog input) won't be read out. and give random values on the SCADA.
remaining 5 analog input cards don't show any problem at all.
the plant ran smoothly for 1-2 weeks. after that we took a shut down and now all of a sudden it declared local fault. the point is that we took a shut down and all the instruments and motors are not on line.
we have put resistors on the scanner and the ASB of the last rack (150 ohms each). the dip switch on the ASB is checked and the baud rate is selected to 57.8.
just to confirm that the chassis and the cards are not faulty, we changed the chassis and cards of slot 6 and 7. still this same problem popped up.
only on rack 3 we face this issue.
what could be the reason of the local fault declaration? how could i get rid of this? can anyone please help me out to resolve this issue?