Section 173.338 - Tungsten hexafluoride(a) Tungsten hexafluoride must be packaged in specification 3A, 3AA, 3BN, or 3E (§§ 178.36 , 178.37 , 178.39 , 178.42 of this subchapter) cylinders. Cylinders must be equipped with a valve protection cap or be packed in a strong outer packaging meeting the provisions of § 173.40 . Outlets of any valves must be capped or plugged. As an alternative, the cylinder opening may be closed by the use of a metal plug. Specification 3E cylinders must be shipped in an overpack that meets the provisions of § 173.40 .(b) In place of the volumetric expansion test, DOT 3BN cylinders used in exclusive service may be given a complete external visual inspection in conformance with part 180, subpart C, of this subchapter, at the time such periodic requalification becomes due. Cylinders that undergo a complete external visual inspection, in place of the volumetric expansion test, must be condemned if removed from tungsten hexafluoride service.74 FR 16143, Apr. 9, 2009, as amended at 75 FR 5395, Feb. 2, 2010