General requirements for shipment of compressed gases in cylinders and spherical pressure vessels.

(a) Gases capable of combining chemically. A cylinder charged with compressed gas must not contain gases or materials that are capable of combining chemically with each other or with the cylinder material so as to endanger its serviceability. See § 173.34(e)(17) regarding the requalification of a cylinder that previously contained a corrosive liquid.

(b) Ownership of container. A container charged with a compressed gas must not be shipped unless it was charged by or with the consent of the owner of the container.

(c) Retest of container. A container for which prescribed periodic retest has become due must not be charged and shipped until such retest has been properly made.

(d) Manifolding containers in transportation. No means of interconnecting such as manifolding of individual containers may be employed for the transportation of compressed gases, except as hereinafter authorized. Containers so manifolded shall be supported and held together as a unit by structurally adequate means. Safety relief devices on manifolded horizontal containers charged with flammable compressed gas shall be arranged to discharge upward and unobstructed to the open air in such a manner as to prevent any impingement of escaping gas upon the containers.

(1) Manifolding is authorized for containers of the following gases: argon, air, carbon dioxide, helium, neon, nitrogen, nitrous oxide, oxygen or sulfur hexafluoride provided that each container is individually equipped with pressure relief devices as required by § 173.34(d) or § 173.315(i).

(2) Manifolding is authorized for specification cylinders containing the following nonliquefied gases: boron trifluoride, carbon monoxide, ethylene, hydrogen, hydrocarbon gases, methane, nitrogen trifluoride, and tetrafluoroethylene, inhibited, except that aluminum cylinders are not authorized for boron trifluoride or nitrogen trifluoride service. Individual cylinders must be equipped with approved pressure relief devices as required by § 173.34(d) or § 173.315(i) of this part. Each cylinder must be equipped with an individual shutoff valve that must be tightly closed while in transit. Manifold branch lines of these individual shutoff valves must be sufficiently flexible to prevent damage to the valves which otherwise might result from the use of rigid branch lines. A temperature measuring device may be inserted in one cylinder of a manifold installation in place of the shutoff valve.

(3) Manifolding is authorized for specification cylinders containing the following gases: 1,1-Difluoroethylene, ethane, ethylene, hydrogen chloride, liquefied hydrocarbon gas, liquefied petroleum gas and propylene, except that aluminum cylinders are not authorized for hydrogen chloride service, provided each cylinder is equipped with approved pressure relief devices as required by § 173.34(d) or § 173.315(i) of this part: and provided further, that each cylinder is equipped with an individual shutoff valve that must be tightly closed while in transit. Each cylinder must be separately charged and means must be provided to insure that no interchange of cylinder contents can occur during transportation. Manifold branch lines to these individual shutoff valves must be sufficiently flexible to prevent injury to the valves which otherwise might result from the use of rigid branch lines.

(4) Manifolding is authorized for containers of acetylene, provided that each container is individually equipped with approved safety relief devices as required by § 173.34(d): And further provided, That each container is equipped with an individual shutoff valve, or valves, which shall be tightly closed while in transit. Manifold branch lines to these individual shutoff valves shall be sufficiently flexible to prevent injury to the valves which otherwise might result from the use of rigid branch lines. All manifold containers shall be transported in a vertical position. For the checking of tare weights or for replacement of solvent the container shall be removed from the manifold. This requirement is not intended to prohibit the charging of the acetylene cylinders while manifolded.

(5) Manifolding is authorized for cargo tanks of the following gas provided individual cargo tanks are equipped with the safety relief valves and gaging devices, as required by § 173.315(h) and (i): And further provided, That each cargo tank is equipped with individual valve, or valves, which shall be tightly closed while in transit and that each such container must be separately charged: Anhydrous ammonia.

(e) Container pressure. The pressure in the container at 70 °F. must not exceed the service pressure for which the container is marked or designated, except as provided in § 173.302(c).

Note 1: In certain cases with liquefied gases the pressure at 70 °F. must be lower than the marked service pressure to avoid having a greater pressure at a temperature of 130 °F. than is permitted.

(1) For authorized containers not marked with a service pressure, the service pressure is designated as follows:

Specification marking Service pressure—psig DOT 3 1,800 3E 1,800 4 300 8 250 9 200 25 300 33 480 38 250 40 200 41 240

(2) For containers made prior to the effective date of specifications, the service pressure is designated as the same as for the same type of container made in accordance with current specifications.

(f) Container pressure at 130 °F. The pressure in the container at 130 °F. shall not exceed 5/4 times the service pressure, except:

(1) Containers charged with acetylene, liquefied nitrous oxide and liquefied carbon dioxide.

(2) When a cylinder is charged in accordance with § 173.302(c), the pressure in the cylinder at 130 °F. must not exceed 5/4 times the filling pressure authorized therein.

(g) Container valve protection. Containers charged with flammable, corrosive, or noxious gases, must have their valves protected by one of the following methods:

(1) By equipping the containers with securely attached metal caps of sufficient strength to protect the valves from injury during transit.

(2) By boxing or crating the containers so as to give proper protection to the valves.

(3) By so constructing the containers that the valve is recessed into the container or otherwise protected so that it will not be subjected to a blow when the container is dropped on a flat surface.

(4) By loading the containers compactly in an upright position and securely bracing in cars or motor vehicles, when loaded by the consignor and to be unloaded by the consignee.

(5) By equipping with valves strong enough to avoid damage during transit for containers containing non-liquefied gas under pressure not exceeding 300 psi at 70 °F.

(h) Compressed gas containers. Compressed gases must be in metal containers built in accordance with the DOT specifications, as shown below, in effect at the time of manufacture, and marked as required by the specification and the regulation for retesting if applicable;

Packagings DOT-2P DOT-3D DOT-4BW DOT-8AL 2Q 3E 4B240ET 91 ICC-3 1 3HT 4C 1CC-251 DOT-3A DOT-3T 4D 261 DOT- 3AL DOT-3AX 4 4DA 331 3A480X 4A 4DS 381 3AA 4AA 4E DOT-39 DOT-3AAX 4B 4L 401 3B 4B240FLW 5 411 3BN 4B240X 1 5F 3C 4BA 8 1 Use of existing cylinders authorized, but new construction not authorized.

(i) Foreign cylinders in domestic use. (1) Except as provided in this section and § 171.12(c) of this subchapter, a charged cylinder manufactured outside the United States may not be offered for transportation to, from, or within the United States unless it has been manufactured, inspected, and tested in accordance with the applicable DOT specification set forth in part 178 of this subchapter.

(2) Effective October 1, 1999, a CTC specification cylinder manufactured, originally marked and approved in accordance with the Canadian Transport Commission (CTC) regulations and in full conformance with the Canadian Transport of Dangerous Goods (TDG) Regulations is authorized for the transportation of a hazardous material to, from or within the United States under the following conditions:

(i) The CTC specification corresponds with a DOT specification and the cylinder markings are the same as those specified in this subchapter except that they were originally marked with the letters “CTC in place of DOT;

(ii) The cylinder has been requalified under a program authorized by the Canadian TDG regulations or requalified in accordance with the requirements in § 173.34(e) within the prescribed requalification period provided for the corresponding DOT specification;

(iii) When the regulations authorize a cylinder for a specific hazardous material with a specification marking prefix of “DOT, a cylinder marked “CTC which otherwise bears the same markings that would be required of the specified “DOT” cylinder may be used; and

(iv) Transport of the cylinder and the material it contains is in all other respects in conformance with the requirements of this subchapter (e.g. valve protection, filling requirements, operational requirements, etc.).

(j) Charging of foreign cylinders for export. (1) A cylinder manufactured outside the United States that has not been manufactured, inspected, tested and marked in accordance with part 178 of this subchapter may be charged with compressed gas in the United States, and shipped solely for export if it meets the following requirements, in addition to other requirements of the subchapter:

(i) It has been inspected, tested and marked (with only the month and year of retest) in conformance with the procedures and requirements of § 173.34(e) or the Associate Administrator for Hazardous Materials Safety has authorized the charging company to fill foreign cylinders under an alternative method of qualification; and

(ii) It meets the maximum filling density and service pressure requirements of this part.

(2) The bill of lading or other shipping paper must identify the cylinder and carry the following certification: “This cylinder has [These cylinders have] been retested and refilled in accordance with DOT requirements for export.”

(k) Outside packagings. Specification 2P, 2Q, 3E, 3HT, 4BA spherical type, 4D, 4DA, 4DS, 91, 39, 401, and 411 must be shipped in strong outside packagings, except that the 4BA spherical type may be securely mounted on pallets to provide protection for the spheres and any attachments.

1 Use of existing cylinders authorized, but new construction not authorized.

(1) Outside packaging must provide protection for the cylinder. Unless the cylinder has a protective collar or neck ring, the outside packaging must provide protection to the valve against accidental functioning and damage.

(l) Specifications 3AX, 3AAX, and 3T cylinders are authorized for transportation only when horizontally mounted on a motor vehicle or in an ISO framework or other framework of equivalent structural integrity. Cylinders may be transported in COFC or TOFC service only under conditions approved by the Associate Administrator for Safety, Federal Railroad Administration. Cylinder valves and safety devices must be protected as follows:

(1) Each cylinder must be fixed at one end of the vehicle or framework with provision for thermal expansion at the opposite end attachment.

(2) The valve and safety relief device protective structure must be sufficiently strong to withstand a force equal to twice the weight involved with a safety factor of four, based on the ultimate strength of the material used; and

(3) Each discharge for a safety relief device on a cylinder containing a flammable gas must be upward and unobstructed.

[29 FR 18743, Dec. 29, 1964. Redesignated at 32 FR 5606, Apr. 5, 1967]

Editorial Note: For Federal Register citations affecting § 173.301, see the List of CFR Sections Affected appearing in the Finding Aids section of this volume.