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Prasannna May 28th, 2003 12:53 AM

PLC Back-up and Restore Test
I am in the process of writing a OQ (Operation Qualification) protocol for testing the back-up and restore of Siemens PLC -S7/400. Appreciate if some one could let me know the test procedure.

The procedure I have written is:

Test #1: Use a Laptop with Step 7 software installed to take the back-up. Create a directory, namely C:\backupcp2.2. Back up the software onto the created directory.

Expected Result for Test#1: PLC software is backed-up

Test#2: Download the software by reloading the back-up software from :/bckupcp2.2(Software backed-up from previous test). Confirm that after reloading the software PID Loop (FIT 400-02) of AHU-600400 is operating satisfactorily.

Expected Result for Test#2: PID Loop FIT 400-02 action is correct.

Any comments on the above test procdure.


Alan Case May 28th, 2003 06:34 AM

Well if the program you backed up is corrupted when you restore to the original PLC the first thing it does is wipe the memory of the PLC, then tries to download the new program. Program corrupted, original program wiped, dead PLC, you looking for new job.
Make the back up then try to go online, if the programs match it will happen, if you backup is no good it wont. This info is valid for ABs so I am not sure of a Siemens.

Allen Nelson May 28th, 2003 07:09 PM

Why OQ
Why are you trying to the Step 7 software? This is essentially what you are trying to do. Verifying that one group of parameters is retained (e.g., your PID settings) doesn't prove that ALL settings are retained.

Is Downloading a new PLC program part of the normal functioning of the process? Will operators be downloading different programs depending on what batch is being run?

If not, all you need to do is write up an SOP on how to backup and restore, and be done with it.

No one (even the FDA) cares how the program gets into the PLC. What they care about is that the program that was in the yesterday (or rather, on the day that it was validated) is the same program as when the batch was made. I don't know Step 7, but if there is a method of getting a serial number (checksum, download date) or some other identification from the downloaded program, then record it, just as you would record the serial number of the PLC. If there is not, then have a section that verifies that the program is the desired one by recording the off-line timestamp (or other info if the pharma has a document control system) and just DO the download. That way, you KNOW what program you are doing your OQ against.

But a test to upload and then down?, forget it.

Of course, that's my take on things. Everyone's validation department is slightly different. But trying to validate Step 7's upload/download ability would be like trying to validate Window's Explorer. At some point, you just have to assume that it works (even though, at times, it crashes.)

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