(g) Manifolding cylinders in transportation. (1) Cylinder manifolding is authorized only under conditions prescribed in this paragraph (g). Manifolded cylinders must be supported and held together as a unit by structurally adequate means. Except for Division 2.2 materials, each cylinder must be equipped with an individual shutoff valve that must be tightly closed while in transit. Manifold branch lines must be sufficiently flexible to prevent damage to the valves that otherwise might result from the use of rigid branch lines. Each cylinder must be individually equipped with a pressure relief device as required in paragraph (f) of this section, except that pressure relief devices on manifolded horizontal cylinders that are mounted on a motor vehicle or framework may be selected as to type, location, and quantity according to the lowest marked pressure limit of an individual cylinder in the manifolded unit. The pressure relief devices selected for the manifolded unit must have been tested in accordance with CGA S–1.1 and CGA S–7. Pressure relief devices on manifolded horizontal cylinders filled with a compressed gas must be arranged to discharge unobstructed to the open air. In addition, for Division 2.1 (flammable gas) material, the pressure relief devices (PRDs) must be arranged to discharge upward to prevent any escaping gas from contacting personnel or any adjacent cylinders. Valves and pressure relief devices on manifolded cylinders filled with a compressed gas must be protected from damage by framing, a cabinet or other method. Manifolding is authorized for cylinders containing the following gases:
(i) Nonliquefied (permanent) compressed gases authorized by §173.302.
(ii) Liquefied compressed gases authorized by §173.304. Each manifolded cylinder containing a liquefied compressed gas must be separately filled and means must be provided to ensure no interchange of cylinder contents can occur during transportation.
(iii) Acetylene as authorized by §173.303.
(2) For the checking of tare weights or replacing solvent, the cylinder must be removed from the manifold. This requirement is not intended to prohibit filling acetylene cylinders while manifolded.
(h) Cylinder valve protection. UN pressure receptacles must meet the valve protection requirements in §173.301b(c). A DOT specification cylinder used to transport a hazardous material must meet the requirements specified in this paragraph (h).
(1) The following specification cylinders are not subject to the cylinder valve protection requirements in this paragraph (h):
(i) A cylinder containing only a Division 2.2 material without a Division 5.1 subsidiary hazard;
(ii) A cylinder containing a Class 8 liquid corrosive only to metal;
(iii) A cylinder with a water capacity of 4.8 liters (293 in3 ) or less containing oxygen, compressed;
(iv) A cylinder containing oxygen, refrigerated liquid (cryogenic liquid);
(v) A Medical E cylinder with a water capacity of 4.9 liters (300 in3 ) or less;
(vi) A fire extinguisher; or
(vii) A “B” style cylinder with a capacity of 40 ft3 (1.13 m3 ) or an “MC” style cylinder with a capacity of 10 ft3 (0.28m3 ) containing acetylene.
(2) For cylinders manufactured before October 1, 2007, a cylinder must have its valves protected by one of the following methods:
(i) By equipping the cylinder with securely attached metal caps of sufficient strength to protect valves from damage during transportation;
(ii) By boxing or crating the cylinders so as to protect valves from damage during transportation;
(iii) By constructing the cylinder so that the valve is recessed into the cylinder or otherwise protected to the extent that it will not be subjected to a blow when the container is dropped onto a flat surface; or
(iv) By loading the cylinders in an upright position and securely bracing the cylinders in rail cars or motor vehicles, when loaded by the consignor and unloaded by the consignee.
(3) For cylinders manufactured on or after October 1, 2007, each cylinder valve assembly must be of sufficient strength or protected such that no leakage occurs when a cylinder with the valve installed is dropped 1.8 m (6 ft.) or more onto a non-yielding surface, such as concrete or steel, impacting the valve assembly or protection device at an orientation most likely to cause damage. The cylinder valve assembly protection may be provided by any method meeting the performance requirement in this paragraph (h)(3). Examples include:
(i) Equipping the cylinder with a securely attached metal cap.
(ii) Packaging the cylinder in a box, crate, or other strong outer packaging conforming to the requirements of §173.25.
(iii) Constructing the cylinder such that the valve is recessed into the cylinder or otherwise protected.
(i) Cylinders mounted in motor vehicles or in frames . (1) MEGCs must conform to the requirements in §173.312. DOT specification cylinders mounted on motor vehicles or in frames must conform to the requirements specified in this paragraph (i).
(2) Seamless DOT specification cylinders longer than 2 m (6.5 feet) are authorized for transportation only when horizontally mounted on a motor vehicle or in an ISO framework or other framework of equivalent structural integrity in accordance with CGA TB–25 (IBR, see §171.7 of this subchapter). The pressure relief device must be arranged to discharge unobstructed to the open air. In addition, for Division 2.1 (flammable gas) material, the pressure relief devices must be arranged to discharge upward to prevent any escaping gas from contacting personnel or any adjacent cylinders.