In the case of flamepaths and joints that are not normally capable of being dismantled in the field, verification of the clearance and flamepath surfaces is not required unless specified specifically by the manufacturer. This does not mean the inspector should do nothing though, the inspector should always validate flamepaths not intended to be dismantled as far as they can reasonably and practicably do so. They should be looking for external signs near, or leading to the flamepath that indicate damage, excessive wear, heat stress and corrosion etc.
It is also important to remember that according to AS/NZS 60079.17 it is normally considered unnecessary to check the diametric clearance of spigot, shaft, spindle and threaded joints, unless there is evidence of wear, distortion, corrosion or other damage, in which case you will need to make reference to the manufacturer’s documents.
“This following information represents and opinion only of a general nature, the specifics of each individual situation must be taken into account with reference to the relevant Legislation, Codes of practice and Australian standards. Professional advice should be sort if there is any doubt.”