ControlLogix Redundancy DISQ

[strauden]

Hi Guys,

I've got a problem with two redundant ControlLogix PLCs using the redundancy modules and I am not very familiar with them.

They were working fine until a few days during an outage. Now the Primary PLC is working fine, however the secondary PLC is in Program Mode (both key switches are in Remote) and the redundancy module on the secondary is stuck in DISQ.

I have tried power cycling both racks and re-seating both modules and tried using the RMCT to synchronize secondary however cannot get the secondary redundancy module back into SYNC or the PLC into RUN mode.

I don't know who has had their fingers on the PLC, could it be that someone turned the keyswitch on the secondary into Program mode and back into Remote? Would that keep the PLC stuck in Remote Program?

I cannot seem change the mode into RUN on the secondary PLC via the software.

Should the secondary PLC be in RUN mode even if it's redundancy module in not SYNCed?

Thanks in advance for your time!

 

[Saturn_Europa1]

Are you getting any errors or faults? Change the keyswitches from Run to Program to Run mode twice to clear the fault.

Do can you ping both controllers? Are the fiber jumpers loose? Is a piece of ethernet loose?

If you cant change the status to run in the software, the first thing I think of is the PLC is not in Remote.

 

[nhatsen]

Now the Primary PLC is working fine, however the secondary PLC is in Program Mode (both key switches are in Remote) and the redundancy module on the secondary is stuck in DISQ.

AFAIK you can't put the secondary PLC in Run mode: that'll happen automatically in case of a switchover.

You need to focus on the DISQ problem. I'd start a re-commisioning of the system:

a) Check all the module's firmware.
b) check copper cables (¿controlnet? ¿ethernet) and FO patch cord.
c) Start the system with one controller. Then turn on the other one.

Do you have MSG blocks running in the logic?

 

[Ken Roach]

For Redundancy systems, my recollection is that you always leave the keyswitches in REMOTE position. The Primary will be in Remote RUN, and the Secondary will be in Remote PROGRAM. The Redundancy Manager modules are in control of the mode of the controllers.

The Redundancy Module Configuration Tool is the best way to figure out what is causing the system to stay Disqualified.

Because it was a power outage that seemed to cause the issue, I would check for something that gets re-set at powerup, like the IP address of an Ethernet module.

Check to find out if there are CompactFlash or SD memory cards in the controllers; maybe one of the controllers has been loaded up with the wrong firmware from an nonvolatile recovery image.

There are separate User Manuals for Standard Redundancy and Enhanced Redundancy in the RA literature library. Just search for "ControlLogix Redundancy User Manual".

 

[ais]

Check to find out if there are CompactFlash or SD memory cards in the controllers; maybe one of the controllers has been loaded up with the wrong firmware from an nonvolatile recovery image.

This is somewhat different, but might be worth considering.
I was commissioning a system with 6 x CompactLogix + Red Lion HMI.
On a week-end the generator went down and the back-up batteries kicked in but were gradually drained over time.
With the HMI's a gradual drain corrupts the loaded program.
Anyway 3 of the HMI's had SD cards in them.
When I restarted the system, the 3 x HMI's programs were re-loaded from the SD cards. Only problem was the programs on the SD cards were not the latest version.
It required me to reload the correct version of the programs into each HMI.

Anyway, that is where I would start i.e. first make sure the program in the PLC and HMI is not corrupted/is the correct version, then start trouble shooting.
This is achieved by (removing SD cards and) simply doing a fresh download.

 

[strauden]

I went to a different site with identical setup and checked, both chassis were in Run mode.

Turned the key to run and back to REM and the controllers sync'ed.