CDL Hazardous Materials Endorsement (HME)Hazardous Materials RegulationsHard
A driver is preparing to transport a cylinder containing UN1072, Oxygen, Compressed (Class 2.2). The cylinder has a marked service pressure of 2000 psi. What is the maximum allowable filling pressure for this cylinder at 70°F (21°C), assuming it is a non-liquefied compressed gas and no special authorization applies?
- A2500 psi
- B2250 psi
- C2000 psi
- DCannot be determined without knowing the gas density.
Show answer & explanationAnswer & explanation
Correct answer: C. 2000 psi
For non-liquefied compressed gases, the filling limit is generally the marked service pressure of the cylinder at 70°F (21°C), unless otherwise specified in the HMR or by a special permit. Therefore, the maximum allowable filling pressure is 2000 psi.
Why the other options are wrong
- A. This value often relates to specific overfill allowances for certain gases or cylinder types, but not a general rule for service pressure.
- B. This value often relates to specific overfill allowances for certain gases or cylinder types, but not a general rule for service pressure.
- D. While gas density is relevant for liquefied gases, for non-liquefied compressed gases, the service pressure is the primary factor for filling limits at standard temperature.
Compressed Gas Cylinder Filling Limits
The maximum allowable filling pressure for non-liquefied compressed gas cylinders is generally limited to the marked service pressure at 70°F (21°C), unless specific regulations or special permits allow for higher pressures.
- Based on cylinder service pressure.
- Standard temperature for calculation is 70°F (21°C).
- Different rules apply for liquefied compressed gases.
- Driver must ensure cylinders are not overfilled.
Memory trick: Service pressure is the ceiling, 70°F is the standard scene!