Plc upgrade with minimum down time?

Hi :

I am working in a manufacturing plant with 150u Siemens plcs.
Now we want to upgrade the system to s7.But the problem is that we must change the racks and wirings and we must stop the plant for a long time.Can anybody please help me how to do it with minimum down time?

Thank You

How many racks are you talking about swapping out?
Can this job be done on the weekend when plant is down?
I would also think that a good part of the time will depend on how qualified your electricians are and the number of electricians you have.
Once it is wired, you should be able to verify all inputs and outputs within a couple of hours, this will also depend on the number of racks you must recheck.

I would suggest you find someone who has done this before and has a GOOD knowledge of Step 7 to help. Have you converted the project to S7? Do you have the hardware running on the bench before installing it?

The best way for safe operation

If you have a very important production that's not allowed to be much interrupted my suggestion is the following....

1. Look for a DP-slave interface and replace the old CPU with this one.
2. Use the existing old I/O's as DP I/O with the new S7 CPU.
Then you can start debugging your new software with no danger. If you have some major problems on Sunday evening, just put back the old CPU and have the plant running again. The next weekend just plugg in the S7 CPU again and continue the testing. Then when the plant have been running a week or two on the new software then you take next step.

3. Remove the old I/O's and install the new. Then you will have the whole weekend just for the signal testing....

This is the best way if you want to have a guaranteed production.

Ronnie Bengtsson
Certified Siemens Solution Provider

That is always difficult to do and needs very very big planning and thinking in advance.
After manufacture and very much testing of all on the bench build the new one in the panel together with the old one.
I replace cooling computers this way.
I can even do this under running time as i can just stop control action on one small section and while i rewire the panel have somebody control the valves.
When it is critical there is always a backup so use that one.
Or you can wait until the plant stops for maintenance or just because of a fault and then replace it.
And yes it involves very long working time.
I would opt to leave it in as long as possible using replace cards.
Please have a good look in local control as this will ease your job. In the old days communication was a big problem now with even internet valves no problem anymore.