...
As used in this section, the word “cylinder” includes UN pressure receptacles. In addition to the definitions contained in §171.8 of this subchapter, the following definitions apply to this subpart:
Commercially free of corrosive components means a hazardous material having a moisture content less than 55 ppm and free of components that will adversely react with the cylinder (e.g., chemical stress corrosion).
Condemn means a determination that a cylinder is unserviceable for the continued transportation of hazardous materials in commerce and that the cylinder may not be restored by repair, rebuilding, requalification, or any other procedure.
Filled or charged means an introduction or presence of a hazardous material in a cylinder.
Mobile unit means a hazardous material having a moisture content less than 55 ppm and free of components that will adversely react with the cylinder (e.g., chemical stress corrosion).
Non-corrosive service means a hazardous material that, in the presence of moisture, is not corrosive to the materials of construction of a cylinder (including valve, pressure relief device, etc.).
Over-heated means a condition in which the temperature of any portion of an aluminum cylinder has reached 176°C (350°F) or higher, or in which the temperature of any portion of a steel or nickel cylinder has reached 343°C (650°F) or higher.
Over-pressurized means a condition in which the internal pressure applied to a cylinder has reached or exceeded the yield point of the cylinder.
Proof pressure test means a liquid-based pressure test by interior pressurization without the determination of a cylinder's expansion.
Rebuild means the replacement of a pressure part (e.g. a wall, head, or pressure fitting) by welding.
Repair means a procedure for correction of a rejected cylinder that may involve welding.
Requalification means the completion of a visual inspection and/or the test(s) required to be performed on a cylinder to determine its suitability for continued service.
Requalification identification number or RIN means a code assigned by DOT to uniquely identify a cylinder requalification, repair, or rebuilding facility.
Test pressure means the pressure used for the requalification of a cylinder.
(1) Water jacket method means a volumetric expansion test to determine a cylinder’s total and permanent expansion by measuring the difference between the volume of water the cylinder externally displaces at test pressure and the volume of water the cylinder externally displaces at ambient pressure.
(2) Direct expansion method means a volumetric expansion test to calculate a cylinder’s total and permanent expansion by measuring the amount of water forced into a cylinder at test pressure, adjusted for the compressibility of water, as a means of determining the expansion.
[67 FR 51660, Aug. 8, 2002, as amended at 71 FR 33894, June 12, 2006; 85 FR 85432, Dec. 28, 2020]