Re: Predictive failures

On 4/17/2024 12:56 AM, Liz Tuddenham wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
 

...When I was designing for pharma, my philosophy was
to make it easy/quick to replace the entire control system.  Let someone
troubleshoot it on a bench instead of on the factory floor (which is
semi-sterile).

 That's fine if the failure is clearly in the equipment itself, but what
if it is in the way it interacts with something outside it, some
unpredictable or unrecognised input codition?  It works perfectly on the
bench, only to fail when put into service   ...again and again.

Then the *replacement* -- now installed in the system -- would have
the same faulty behavior as the "pulled" unit.  Lending credibility
to the pulled unit NOT being at fault.
When the control system is a 7 ft tall, 24 inch rack, bolted to
the floor, your only option is to troubleshoot the system there,
taking the system out of production while doing so.