Meeting HACCP Requirements of GFSI Benchmarked Standards

Is Receiving of Materials considered as a CCPs?

my operation uses metal detector as CCP and as I understand it they all have different detection sensitivity, is there a widely/accepted guidance on how small should the metal detector able to detect for certain food category? e.g. oil, fats, flour, sugar, rice ,etc

Is Receiving of Materials considered as a CCPs?

Frequently these days regarded as PRPs, especially if iso-haccp oriented, but some people still use CCPs.

my operation uses metal detector as CCP and as I understand it they all have different detection sensitivity, is there a widely/accepted guidance on how small should the metal detector able to detect for certain food category? e.g. oil, fats, flour, sugar, rice ,etc

I'm afraid the global answer is No.

Yr question is really asking as to whether there is an accepted maximum size for "non-hazardous" metal fragments. Same answer.