I believe what ISO 17025 means by "standard" is a published standard. ISO 17025 says that it is preferable to use international (ISO), regional, and national (NIST, ASME) standards. I think you're covered there. As for OEM procedures, those I do not believe are considered "standard", though they generally manufacture the equipment to some standard (ASME, IEEE, etc.). You could also look in to GIDEP, if you already have not.