Ask X3What does 49 CFR 178.277 (Requirements for the design, construction, inspection and testing of portable tanks intended for the transportation of refrigerated liquefied gases) require?
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According to 49 CFR 178.277, portable tanks intended for the transportation of refrigerated liquefied gases must meet the following general design and construction requirements:
* Construction & Certification: They must be of seamless or welded steel construction, have a water capacity greater than 450 liters (118.9 gallons), and be designed, constructed, certified, and stamped in accordance with Section VIII of the ASME Code.
* Heat Treatment & Radiography: Tanks must be postweld heat treated and radiographed as prescribed in Sections V and VIII of the ASME Code. Tanks built under part UHT must be postweld heat treated as a unit after all welds to the shell and heads are completed, at a tank metal temperature of no less than 1,050 °F.
* Welding Procedures: Welding procedures and welder performance tests must be performed annually in accordance with Section IX of the ASME Code, accounting for specific essential variables (number of passes, plate thickness, heat input per pass, and specified rod and flux, which cannot vary by more than 25% from procedure qualification). Records must be retained for at least 5 years by the manufacturer.
* Materials: Shells and jackets must be made of metallic materials suitable for forming (jackets must be made of steel). Materials must account for the minimum design temperature to prevent brittle fracture, hydrogen embrittlement, stress corrosion cracking, and impact damage. Parts coming into contact with the refrigerated liquefied gas must be compatible with it.
* Insulation: The tank must include a complete thermal insulation system covering the shell, protected by a steel jacket to prevent moisture and damage. Gas-tight jackets must have a device to prevent dangerous pressure in the insulation space. Materials that can dangerously react with oxygen or oxygen-enriched atmospheres cannot be used near thermal insulation where contact is possible if the gas has a boiling point below minus 182 °C at atmospheric pressure. Insulation effectiveness must not deteriorate in service.
* Holding Time & Testing: A reference holding time must be determined for each gas through testing (as specified in § 178.338-9), considering insulation effectiveness, lowest set pressure, initial filling conditions, an assumed 30 °C (86 °F) ambient temperature, and the physical properties of the gas. Insulation effectiveness (heat influx) must be determined via type testing (constant pressure or closed system tests).
* Jackets: The jacket of a vacuum-insulated double-wall tank must have an external design pressure of at least 100 kPa (1 bar) gauge pressure, or a calculated critical collapsing pressure of at least 200 kPa (2 bar) gauge pressure.
* Design Criteria: For shells with vacuum insulation, the test pressure must be at least 1.3 times the sum of the maximum allowable working pressure (MAWP) and 100 kPa (1 bar), and in no case less than 300 kPa (3 bar) gauge pressure.
* Service Equipment: Filling and discharge openings for flammable refrigerated liquefied gases must be fitted with at least three mutually independent shut-off devices in series (beginning with a stop-valve as close as reasonably practicable to the jacket).