49 C.F.R. § 178.270-10 External design pressure.
Title 49 - Transportation
(a) Each portable tank not fitted with vacuum relief devices must be designed to withstand a positive external pressure differential of at least 0.4 bar (6 psig). (b) Each portable tank fitted with vacuum relief devices must be designed to withstand a positive external pressure differential not less than the set pressure of the vacuum relief device and in any case at least 0.21 bar (3 psig). [Amdt. 178–65, 46 FR 9896, Jan. 29, 1981, as amended at 66 FR 45387, Aug. 28, 2001]
Title 49: Transportation
PART 178—SPECIFICATIONS FOR PACKAGINGS
Subpart H—Specifications for Portable Tanks
§ 178.270-10 External design pressure.
