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CDL · Liquid Surge

How do baffled tanks differ from smooth-bore tanks in how they handle surge?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Baffled tanks have bulkheads with holes that slow forward-and-back surge but do little to control side-to-side surge, while smooth-bore tanks have nothing inside to slow surge in any direction

  1. A Baffled tanks have bulkheads that completely separate compartments and eliminate all surge
  2. B Smooth-bore tanks control surge better than baffled tanks
  3. C There is no handling difference between the two
  4. D Baffled tanks have bulkheads with holes that slow forward-and-back surge but do little to control side-to-side surge, while smooth-bore tanks have nothing inside to slow surge in any direction

Why this is the answer

Baffled liquid tanks have bulkheads with holes that let liquid flow through while dampening the front-to-back wave action, which reduces forward surge during braking. However, baffles do not stop side-to-side surge, so the driver must still be careful in turns and lane changes. Smooth-bore tanks have no baffles at all, so surge is strong in every direction; these are typically used for food products where baffles would be hard to clean. Knowing which type you are driving tells you how much surge to expect and how cautiously to brake and steer. Bulkheads (solid walls separating compartments) are a different feature used to separate cargo or balance weight.
Source: FMCSA CDL Manual 8.2.3 Baffled vs Smooth Bore Tanks

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About this topic: Liquid Surge

Liquid surge is the forward-and-back movement of a partially filled tank, strong enough to push a stopped truck into an intersection. These questions cover why it happens, how baffles and bulkheads limit it, and how to brake and stop to control it. This is one of 10 Tanker questions on liquid surge, each with a full explanation on a single study page.

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