1. Between any of the activity conducted such as calibration, monitoring activity and the activity conducted by the metal detector expert, is there any instance that for a particular (or group) of product that the metal detector settings have been changed? If yes, what could be the cause of the change in settings?
2. For the settings to be established, what is the procedure? Also between the 3 activities, how is it different, the number of testing the test pieces?
The reason I asked the question is that, if everything still stands for the 1st time since it was commissioned and no interference from the environment (such as heavy vibration, good grounding etc) that the setting should not change as you have established it based on the worst case scenario. If the settings changes from time to time for a specific product then it could not be "validated".
The scheme of what we do, the difference is that for:
Validation (checked initially with 3rd party expert) - the installation for MD is 1st check for any possible interference and wand test is performed. Setting is established step considering nature of product and its orientation (including line speed). The efficiency of the MD is established. The efficiency in terms of it should only alarm in the presence of contaminant. Then with the settings established, statistically checked for efficiency of metal detection (with test piece) and have a conclusion.
Verification - months data is review in terms rejection rate without contaminant being found. Check settings, if found the same, pass test piece on a lesser repetition.
3rd party contractor (the MD expert) check motherboard and if still ok, do wand test to check interference,if ok, will be left as found and just test certain number of pieces as "handshake". If found with defective then, rectify issue, if it changes setting, "revalidation" would be necessary.