49 CFR §179.500-3

1. (a)Tanks built under this specification shall be hollow forged or drawn in one piece. Forged tanks shall be machined inside and outside before ends are necked-down and, after necking-down, the ends shall be machined to size on the ends and outside diameter. Machining not necessary on inside or outside of seamless steel tubing, but required on ends after necking-down.
2. (b)For tanks made in foreign countries, chemical analysis of material and all tests as specified must be carried out within the limits of the United States under supervision of a competent and disinterested inspector; in addition to which, provisions in § 179.500-18 (b) and (c) shall be carried out at the point of manufacture by a recognized inspection bureau with principal office in the United States.
3. (c)The term “marked end” and “marked test pressure” used throughout this specification are defined as follows:
   1. (1)“Marked end” is that end of the tank on which marks prescribed in § 179.500-17 are stamped.
   2. (2)“Marked test pressure” is that pressure in psig which is indicated by the figures substituted for the **** in the marking DOT-107A **** stamped on the marked end of tank.
4. (d)The gas pressure at 130 °F in the tank shall not exceed 7/10 of the marked test pressure of the tank.