CDL Hazardous Materials Endorsement (HME)Bulk Tanks and Other ContainersHard
A portable tank is designed for the transport of liquid hazardous materials. It has a test pressure of 6.0 bar. According to UN portable tank regulations, what is the maximum allowable working pressure (MAWP) for this tank?
- A3.0 bar
- B6.0 bar
- C4.0 bar
- D4.8 bar
Show answer & explanationAnswer & explanation
Correct answer: C. 4.0 bar
For UN portable tanks, the maximum allowable working pressure (MAWP) is typically specified as two-thirds (2/3) of the minimum test pressure. Therefore, 2/3 * 6.0 bar = 4.0 bar.
Why the other options are wrong
- A. This is 1/2 of the test pressure, which is incorrect.
- B. The MAWP cannot be equal to the test pressure; the test pressure is always higher to ensure a safety margin.
- D. This value (4.8 bar) is 80% of the test pressure, which is incorrect.
UN Portable Tank MAWP to Test Pressure Ratio
For UN portable tanks, the Maximum Allowable Working Pressure (MAWP) is generally established as two-thirds (2/3) of the minimum test pressure to ensure a safety margin.
- MAWP = 2/3 * Test Pressure.
- Test pressure is always higher than MAWP.
- Ensures structural integrity under operating conditions.
Memory trick: MAWP is two-thirds safe, tested at full force.