Multiple Panelview Plus 6's and Compactlogix PLC's

Working on a project where we would have two pieces of equipment (say A & B) each with a 1769-L30ER and a Panelview Plus 6 600. There is also some shared loading equipment (say C) that would have a 1769-L18 PLC and no HMI.

Can I have the L18 communicate to both Panelviews as well as both PLC's?

The idea would be to have a screen on both HMI's to operate the L18 equipment. This way either equipment A or B could be shut down and A&C or B&C could still run. There would also be messaging (produced/consumed tags?) between the A&C and B&C PLC's.

Is this feasible, or am I asking for trouble here?

Sure, if you have a lockout scheme to prevent 2 panels from taking control. Put the control logic in the L18. Monitoring tags could be identical in all the HMI's, however to make it easier to lockout and troubleshoot, any control bits should be in separate areas of mapped memory to the HMI's. You could lock it out using the Screen number register on the HMI's. One thing to keep in mind, its probably best to only control something that can be seen from the HMI and as always the machines should be adequately guarded by a safety system outside the control of the PLC's. Even so, people do stupid things and best to be able to see what you are controlling.

The trick is to run the networking from A and B into C so that dropping A or B doesn't stop comms to C and the remaining machine.

The screens will happily talk to multiple PLCs and the PLCs will have no problems producing tags to more than one consumer.

Put connection status bits into the produced tags then you can put logic to handle the absence of A or B from C.

You can have both screens with the same tags in C if you are lazy but as ATU says it allows the operators to do stupid things when both machines are running.

Usually in this setup the hardest thing to get working is any safety interlocks between the machines when one member is missing.

Thanks for the advice guys. After thinking about it a little more, I think we'll just put a small HMI on the loading table. For about $600 it doesn't seem worth the hassle.

I think this falls under the category of "just because you can doesn't mean you should".

If you consider your time writing and debugging, it may also be the most economical choice.