Tank Vehicles
What this domain tests
Tank vehicle questions focus on liquid surge, baffles, outage space, vents, and the high center of gravity. The exam tests whether you can predict how a partly filled tank will behave.
Core rules
- Liquid moves inside a tank. Starting, stopping, and turning cause surge that pushes the vehicle.
- Baffles divide the tank and reduce surge, but they do not eliminate it. A smooth-bore tank has the strongest surge.
- Keep the tank’s center of gravity low and drive smoothly. Brake and accelerate gently, and slow down before curves.
- Tanks need outage space for expansion, commonly about 1 percent of capacity. Never fill to the brim.
- Check manholes, vents, hoses, and valves. A blocked vent can cause pressure problems.
- No smoking around tank vehicles, and follow hazardous materials rules when the cargo requires them.
Worked example
A 5,000-gallon tank needs about 1 percent outage, or 50 gallons of empty space. If the driver fills it completely, heat or movement can force liquid out through the vent or damage the tank. On a partly filled smooth-bore tank, a hard stop sends liquid forward, then it surges back; the driver should brake earlier and more gently than with a dry van.
Traps that cost marks
Treating baffles as a complete cure for surge; filling a tank to the top; braking hard with a partial load; ignoring vents and valves; and taking curves at the same speed as a box trailer.