Re: How to determine the PM and Calibration grace periods ?
I think the general answer is none. I ran a high quality calibration lab a few years back where they were so strict that anyone who did not turn in their instruments on time got into trouble. They had about zero tolerance for late turn ins for calibration.
The philosophical answer is that the interval is the defined period of time to a given confidence that an instrument can be expected to remain in its specifications.
It is often written into quality systems to allow for extensions to calibration interval based on historical performance (if there is data to support that the instrument has a documented probability to remain within specifications).
If you don't have to comply with any ISO or other document, some companies to write into policy the ability to includle a grace period. But, if you are audited by an ISO auditor or other such auditor, you might have to defend such actions.
One way I can think of to build in a legitimate (in my opinion) "grace period" would be to make the due date 15 days prior to the end of the interval. For a one year calibration, if you calibrated on Jan 15 2013, the due date could be Dec 31 2013, but you have to define in your quality system that the due date will occur 15 days prior to the defined interval. The subsequent 15 day period could be the "grace period" (but you might not want to use that term) - perhaps say you allow that 15 day window for the instrument to be delivered for calibration. You could get your grace period and still abide by the defined intervals. Just my thoughts. Perhaps others may find a problem with the idea.
