CFR > Title 30 - Mineral Resources > CHAPTER I—MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR > SUBCHAPTER B—TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS (parts 5 to 36) > PART 7—TESTING BY APPLICANT OR THIRD PARTY > SUBPART J—Electric Motor Assemblies (§7.301 to §7.311) > 7.305—Critical characteristics.

7.305—Critical characteristics.

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.