49 CFR § 178.320 - General requirements applicable to all DOT specification cargo tank motor vehicles.
(a) Definitions. For the purpose of this subchapter:
Baffle means a non-liquid-tight transverse partition device that deflects, checks or regulates fluid motion in a tank.
Cargo tank means a bulk packaging that:
(1) Is a tank intended primarily for the carriage of liquids, gases, solids, or semi-solids and includes appurtenances, reinforcements, fittings, and closures (for tank, see §§ 178.337–1, 178.338–1, or 178.345–1, as applicable);
(2) Is permanently attached to or forms a part of a motor vehicle, or is not permanently attached to a motor vehicle but that, by reason of its size, construction, or attachment to a motor vehicle, is loaded or unloaded without being removed from the motor vehicle; and
Cargo tank wall means those parts of the cargo tank that make up the primary lading retention structure, including shell, bulkheads, and fittings and, when closed, yield the minimum volume of a completed cargo tank motor vehicle.
Connecting structure means the structure joining two cargo tanks.
Constructed and certified in accordance with the ASME Code means a cargo tank is constructed and stamped in accordance with Section VIII of the ASME Code (IBR, see § 171.7 of this subchapter), and is inspected and certified by an Authorized Inspector.
Constructed in accordance with the ASME Code means a cargo tank is constructed in accordance with Section VIII of the ASME Code with authorized exceptions (see §§ 178.346 through 178.348) and is inspected and certified by a Registered Inspector.
Design type means one or more cargo tanks that are made—
(1) To the same specification;
(2) By the same manufacturer;
(4) Of the same materials of construction;
(5) To the same cross-sectional dimensions;
(6) To a length varying by no more than 5 percent;
(7) With the volume varying by no more than 5 percent (due to a change in length only); and
(8) For the purposes of § 178.338 only, with the same insulation system.
Extreme dynamic loading means the maximum loading a cargo tank motor vehicle may experience during its expected life, excluding accident loadings resulting from an accident, such as overturn or collision.
Flange means the structural ring for guiding or attachment of a pipe or fitting with another flange (companion flange), pipe, fitting or other attachment.
Inspection pressure means the pressure used to determine leak tightness of the cargo tank when testing with pneumatic pressure.
Internal self-closing stop valve means a self-closing stop valve designed so that the self-stored energy source is located inside the cargo tank or cargo tank sump, or within the welded flange, and the valve seat is located within the cargo tank or within one inch of the external face of the welded flange or sump of the cargo tank.
Loading/unloading connection means the fitting in the loading/unloading line farthest from the loading/unloading outlet to which the loading/unloading hose, pipe, or device is attached.
Manufacturer means any person engaged in the manufacture of a DOT specification cargo tank, cargo tank motor vehicle, or cargo tank equipment that forms part of the cargo tank wall. This term includes attaching a cargo tank to a motor vehicle or to a motor vehicle suspension component that involves welding on the cargo tank wall. A manufacturer must register with the Department in accordance with subpart F of part 107 in subpart A of this chapter.
Maximum allowable working pressure or MAWP means the maximum pressure allowed at the top of the tank in its normal operating position. The MAWP must be calculated as prescribed in Section VIII of the ASME Code. In use, the MAWP must be greater than or equal to the maximum lading pressure conditions prescribed in § 173.33 of this subchapter for each material transported.
Maximum lading pressure. See § 173.33(c).
Minimum thickness means the minimum required shell and head (and baffle and bulkhead when used as tank reinforcement) thickness needed to meet the specification. The minimum thickness is the greatest of the following values: (1)(i) For MC 330, MC 331, and MC 338 cargo tanks, the specified minimum thickness found the applicable specification(s); or
(ii) For DOT 406, DOT 407 and DOT 412 cargo tanks, the specified minimum thickness found in Tables I and II of the applicable specification(s); or
(iii) For MC 300, MC 301, MC 302, MC 303, MC 304, MC 305, MC 306, MC 307, MC 310, MC 311, and MC 312 cargo tanks, the in-service minimum thickness prescribed in Tables I and II of § 180.407(i)(5) of this subchapter, for the minimum thickness specified by Tables I and II of the applicable specification(s); or
(2) The thickness necessary to meet with the structural integrity and accident damage requirements of the applicable specification(s); or
(3) The thickness as computed per the ASME Code requirements (if applicable).
Normal operating loading means the loading a cargo tank motor vehicle may be expected to experience routinely in operation.
Nozzle means a subassembly consisting of a pipe or tubular section with or without a welded or forged flange on one end.
Outlet means any opening in the shell or head of a cargo tank, (including the means for attaching a closure), except that the following are not outlets: a threaded opening securely closed during transportation with a threaded plug or a threaded cap, a flanged opening securely closed during transportation with a bolted or welded blank flange, a manhole, a gauging device, a thermometer well, or a pressure relief device.
Pipe coupling means a fitting with internal threads on both ends.
Self-closing stop valve means a stop valve held in the closed position by means of self-stored energy, that opens only by application of an external force and that closes when the external force is removed.
Shell means the circumferential portion of a cargo tank defined by the basic design radius or radii excluding the bulkheads.
Stop valve means a valve that stops the flow of lading.
Tank means a container, consisting of a shell and heads, that forms a pressure tight vessel having openings designed to accept pressure tight fittings or closures, but excludes any appurtenances, reinforcements, fittings, or closures.
Test pressure means the pressure to which a tank is subjected to determine structural integrity.
Toughness of material means the capability of a material to absorb energy represented by the area under a stress strain curve (indicating the energy absorbed per unit volume of the material) up to the point of rupture.
Variable specification cargo tank means a cargo tank that is constructed in accordance with one specification, but that may be altered to meet another specification by changing relief device, closures, lading discharge devices, and other lading retention devices.
Welded flange means a flange attached to the tank by a weld joining the tank shell to the cylindrical outer surface of the flange, or by a fillet weld joining the tank shell to a flange shaped to fit the shell contour.
(b) Design certification.
(1) Each cargo tank or cargo tank motor vehicle design type, including its required accident damage protection device, must be certified to conform to the specification requirements by a Design Certifying Engineer who is registered in accordance with subpart F of part 107 of this title. An accident damage protection device is a rear-end protection, overturn protection, or piping protection device.
(2) The Design Certifying Engineer shall furnish to the manufacturer a certificate to indicate compliance with the specification requirements. The certificate must include the sketches, drawings, and calculations used for certification. Each certificate, including sketches, drawings, and calculations, shall be signed by the Design Certifying Engineer.
(c) Exceptions to the ASME Code. Unless otherwise specified, when exceptions are provided in this subpart from compliance with certain paragraphs of the ASME Code, compliance with those paragraphs is not prohibited.