# 180.203 Definitions.
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 vehicle specifically authorized under a RIN to carry out requalification operations identified under the RIN within specified geographic areas away from the principle place of business. Mobile units must comply with the requirements outlined in the approval issuance letter from the Associate Administrator for Hazardous Materials Safety (see § 107.805 of subchapter A of this chapter).
*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.
*Permanent expansion* means a permanent increase in a cylinder's volume after the test pressure is released.
*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.
[67 FR 51660, Aug. 8, 2002, as amended at 71 FR 33894, June 12, 2006; 85 FR 85432, Dec. 28, 2020]