49 CFR 173.316 - Cryogenic liquids in cylinders.
(4) A valve or fitting made of aluminum with internal rubbing or abrading aluminum parts that may come in contact with oxygen in the cryogenic liquid form may not be installed on any cylinder used to transport oxygen, cryogenic liquid unless the parts are anodized in accordance with ASTM Standard B 580 (IBR, see § 171.7 of this subchapter).
(6) Each cylinder must be provided with one or more pressure relief devices, which must be installed and maintained in compliance with the requirements of this subchapter.
(7) Each pressure relief device must be installed and located so that the cooling effect of the contents during venting will not prevent effective operation of the device.
(8) All pressure relief device inlets must under maximum filling conditions be situated in the vapor space of the closed cryogenic receptacle and the devices must be arranged to ensure that the escaping vapor is discharged unobstructed.
(b)Pressure control systems. Each cylinder containing a cryogenic liquid must have a pressure control system that conforms to § 173.301(f) and is designed and installed so that it will prevent the cylinder from becoming liquid full.
(c)Specification cylinder requirements and filling limits. Specification DOT-4L cylinders ( § 178.57 of this subchapter) are authorized for the transportation of cryogenic liquids when carried in the vertical position as follows:
(1) For purposes of this section, “filling density,” except for hydrogen, is defined as the percent ratio of the weight of lading in the packaging to the weight of water that the packaging will hold at 60 °F. (1 lb. of water = 27.737 cubic inches at 60 °F.).
(2) The cryogenic liquids of argon, nitrogen, oxygen, helium and neon must be loaded and shipped in accordance with the following table:
|Pressure control valve setting (maximum start-to-discharge pressure psig)||Maximum permitted filling density (percent by weight)|
|Design service temperature (°F.)||−320||−320||−320||−320||−452||−411|
(3) Hydrogen (minimum 95 percent parahydrogen) must be loaded and shipped as follows:
|Column 1||Column 2|
|Design service temperature||Minus 423 °F. or colder.|
|Maximum permitted filling density, based on cylinder capacity at minus 423 °F (see Note 1)||6.7 percent.|
|The pressure control valve must be designed and set to limit the pressure in the cylinder to not more than||17 psig.|
The filling density for hydrogen, cryogenic liquid is defined as the percent ratio of the weight of lading in a packaging to the weight of water that the packaging will hold at minus 423 °F. The volume of the packaging at minus 423 °F is determined in cubic inches. The volume is converted to pounds of water (1 lb. of water = 27.737 cubic inches).
(i) Each cylinder must be constructed, insulated and maintained so that during transportation the total rate of venting shall not exceed 30 SCF of hydrogen per hour.
(ii) In addition to the marking requirements in § 178.35 of this subchapter, the total rate of venting in SCF per hour (SCFH) shall be marked on the top head or valve protection band in letters at least one-half inch high as follows: “VENT RATE**SCFH” (with the asterisks replaced by the number representing the total rate of venting, in SCF per hour).
(iii) Carriage by highway is subject to the conditions specified in § 177.840(a) of this subchapter.
(d)Mixtures of cryogenic liquid. Where charging requirements are not specifically prescribed in paragraph (c) of this section, the cryogenic liquid must be shipped in packagings and under conditions approved by the Associate Administrator.