Section 7.305 - Critical characteristicsThe 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.