Is there any difference if it comes from an Ex repair facility or from manufacturer itself?
en/iec 60079-19 says not any difference. Under IEC ist does even mean it shall be certified accordingly by a 3rd party (IECEx CB). Under ATEX the way to go is much simpler.
All 3 conditions shall be met:
– audited QMS based on ISO 9001
– proper tools
– competent personnel
Note: most of the cases this is the reason why manufacturers better deliver a new product as full replacement than do repair for the same.
Keep up good work!