The following critical characteristics shall be inspected on each motor assembly to which an approval marking is affixed:
(a) Finish, width, and planarity of surfaces that form any part of a flame-arresting path.
(b) Clearances between mating parts that form flame-arresting paths.
(c) Thickness of walls, flanges, and covers that are essential in maintaining the explosion-proof integrity of the enclosure.
(d) Spacing of fastenings.
(e) Length of thread engagement on fastenings and threaded parts that assure the explosion-proof integrity of the enclosure.
(f) Use of lockwasher or equivalent with all fastenings.
(g) Dimensions which affect compliance with the requirements for packing gland parts in § 7.304 of this part.