CDL Hazardous Materials Endorsement (HME)Bulk Tanks and Other ContainersEasy
A driver is transporting a liquid hazardous material in a cargo tank. The cargo tank must be equipped with an internal self-closing stop valve for each opening below the liquid level. What is the primary purpose of this valve?
- ATo allow for manual venting of pressure buildup within the tank.
- BTo prevent overfilling of the tank during loading operations.
- CTo prevent the uncontrolled release of hazardous material in case of external piping damage.
- DTo facilitate the complete drainage of the tank during unloading.
Show answer & explanationAnswer & explanation
Correct answer: C. To prevent the uncontrolled release of hazardous material in case of external piping damage.
Internal self-closing stop valves are a crucial safety feature. Their primary purpose is to automatically prevent the escape of hazardous material from the tank in the event that external piping, hoses, or valves are damaged or broken off during an accident or incident.
Why the other options are wrong
- A. Pressure relief is handled by separate pressure relief devices, not the internal stop valve.
- B. Overfilling prevention is typically managed by other devices like level sensors or visual outage checks.
- D. While it controls flow, its primary safety purpose is containment during damage, not drainage facilitation.
Internal Self-Closing Stop Valve
A safety valve located inside a cargo tank, designed to automatically close and prevent the release of hazardous material from below-liquid-level openings if external piping or fittings are damaged.
- Located inside the tank.
- Self-closing mechanism.
- Prevents uncontrolled release during external damage.
- Required for liquid hazardous materials.
Memory trick: Safety valves: Stop the flow, prevent the blow, relieve the pressure, and measure the level.