Hi All,

I have a topic that I need some help with. Our plant was recently audited by an external auditor and one of the findings was that we don't regularly check our backups to see if they are actually valid or recoverable.

My argument was that how would I know my PLC project that has been backed up is correct unless I physically download it to the processor to check?

Does anyone know of any industry best practises when it comes to checking of backups?

Thanks,
Shaun

 

Hi,

Most programming packages allow a compare function with the source code, is this is OK then you can recreate the program if needed. It can normally be done remoteley withut stopping the PLC

Marc Sinclair
http://www.germainesystems.eu

 

I have seen a lot of corrupt PLC back-ups, so your auditor has a valid point. You haven't lived until you've been asked to look at (fix) a critical machine that has been down for close to a week, and whose every program back-up copy is corrupt.

Many PLC programming packages let you compare on-line to off-line copies to see if the copy in your PLC CPU matches the copy on your hard drive. In this case the simplest solution is:

1) After finally accepting the changes which have been made to the PLC (according to whatever test and acceptance procedures you have), do an on-line to off-line compare. If they match, you know that what is in the CPU matches the copy on your hard drive.

2) Store the validated copy to a central archive location (normally a structured set of directories on your network). Only one or a very few people should have write access to this archive location (read access though should be unrestricted). You might as well find all the CAD files of the electrical schematics, the servo drive configurations, the MMI programs, and the PDFs of the OEM literature while you are at it, and put them in there too.

3) Record the file date and the reason for the change in a change log.

Item "0" should be "write a procedure specifying steps 1 to 3 must be followed by all personnel or outside contractors", and have this procedure signed by the appropriate management personnel. This procedure should be the first thing you show the auditor.

There are more sophisticated (including completely automated) solutions, but the above should satisfy an auditor.

 

why don't you shutdown the hot PLC so the backup work and youll see if it works. Arent the both programs equal?