Michigan CDL Tanker key terms

The forward and backward movement of liquid cargo inside a partly filled tank as the vehicle speeds up, slows down, or turns. Surge pushes against the tank ends and shifts weight, making the rig harder to control.

An internal wall or plate inside a tank that divides the liquid into smaller sections to reduce front-to-back surge. Baffles have holes or openings that let liquid pass slowly between compartments.

A tank built with internal dividers that limit how far liquid can slosh in one motion. It reduces surge compared with a smooth bore tank, but it does not eliminate surge, so drivers still slow down and brake gently.

A tank with no internal baffles, so the liquid moves freely from end to end as one mass. Surge forces are strongest in these tanks, requiring slower speeds, longer following distance, and very gentle braking.

A separate section inside a tanker created by bulkheads, each holding its own product. Compartments let one vehicle carry different liquids and help control weight distribution by loading them in a planned order.

A solid internal wall that separates tank compartments and keeps different products from mixing. Unlike a baffle, a bulkhead normally has no openings for liquid to flow through during driving.

The empty space left above the liquid surface in a tank or compartment. It allows for expansion of the product as temperature rises and provides room for movement, but too much outage increases surge.

A condition where most of the vehicle's weight sits high above the road, as with a loaded tanker. It makes the vehicle easier to roll over in curves or sudden steering, so speed must be reduced well before turns.

A crash in which the vehicle tips onto its side or roof. Tankers are prone to rollover because of their high center of gravity and liquid movement, especially when taking curves or ramps too fast.

Slowing down before entering a curve or ramp rather than braking while turning. With liquid cargo, braking in a curve combines surge forces with cornering forces and can cause a skid or rollover.

The actions taken to regain control when wheels lose traction. With tankers, releasing the brakes and steering gently in the direction you want to go helps, but surge may still push the vehicle, so avoid hard corrections.

A skid in which the trailer's rear wheels lose traction and the trailer moves sideways out of line with the tractor. Liquid surge can trigger it during braking or sudden steering, and it can lead to jackknifing.

A condition where the tractor and trailer fold against each other at a sharp angle, often after the drive or trailer wheels lock or lose traction. Gentle braking and steady steering help prevent it.

The total distance needed to bring the vehicle to a complete stop, including perception, reaction, and braking distance. A loaded tanker needs much more room because of its weight and the forward push of liquid surge.

The gap kept between your vehicle and the one ahead. Tanker drivers should allow extra space because liquid surge lengthens stopping distance and because sudden stops can send product rushing forward.

The setting that keeps air brake pushrods within proper travel limits so brakes apply fully and evenly. Out-of-adjustment brakes on a heavy tanker reduce stopping power and can cause pulling or wheel lockup.

A test of the air brake system for leaks, proper pressure build-up, and correct warning signals. Tanker drivers perform it before driving because heavy loads demand reliable braking on downgrades and in traffic.

A required walk-around check of the vehicle before driving. For tankers it includes looking for leaks, checking hoses, valves, domes, and placards, and confirming the tank and fittings are secure.

A close examination of the tank shell, fittings, valves, piping, and vents for damage, corrosion, or leaks. Any defect that could cause a spill must be reported and corrected before the vehicle is loaded or moved.

Looking, listening, and sometimes smelling for escaping product around valves, flanges, hoses, and hatches. Leaks on a tanker create fire, health, and environmental hazards, so loading must stop if one is found.

The controlled release of pressure or vapor from a tank through vents or relief devices. Proper venting prevents tanks from over-pressurizing or collapsing during loading, unloading, and temperature changes.

A system that captures vapors displaced from a tank during loading or unloading instead of releasing them to the air. It reduces fire risk and pollution and requires secure hose connections and careful attention to valves.

Filling a tank through connections at its lower side rather than through the top. It reduces static electricity and vapor generation, and it is common at terminals that use vapor recovery equipment.

Filling a tank through an opening on top, often with a drop tube reaching near the bottom. Without a drop tube, falling product can create static and vapors, so bonding and grounding are essential.

A pipe lowered into a tank during top loading so the product enters near the liquid surface. It reduces splashing, vapor generation, and static buildup compared with letting liquid fall freely.

An electric charge that builds up when liquids or vehicles move and can spark when it discharges. Bonding and grounding the vehicle and equipment before loading or unloading prevents ignition of flammable vapors.

Connecting the vehicle and loading equipment so they share the same electrical charge, then connecting them to earth. This drains static electricity safely before flammable product or vapor is present.

A liquid that gives off vapors capable of igniting at normal working temperatures. Its vapors are often heavier than air and can travel to an ignition source, so keep sources away and follow placarding rules.

A diamond-shaped warning sign placed on the vehicle to identify the hazard class of the cargo. Placards warn emergency responders and the public and must match the product actually in the tank.

The document describing the hazardous material being transported, including its proper shipping name, hazard class, and quantity. It must be kept within reach and given to emergency responders if an incident occurs.

Guidance carried with hazardous cargo that tells responders and the driver what to do during a spill, fire, or exposure. It includes the product's hazards and basic first-aid and firefighting steps.

The special endorsement added to a CDL that allows driving vehicles carrying certain hazardous materials. It requires a knowledge test, a security threat assessment, and compliance with specific rules.

The CDL endorsement required to drive a vehicle that carries liquid or gaseous cargo in a permanently mounted tank above a set capacity. It is obtained by passing a tanker knowledge test.

A system that prevents wheels from locking during hard braking by rapidly adjusting brake pressure. On a tanker it helps keep steering control, but it does not overcome the forces created by liquid surge.

The ability of a vehicle to resist tipping sideways in turns or sudden maneuvers. Tankers have less roll stability when loaded high, so drivers reduce speed and avoid abrupt steering.

How cargo weight is spread across axles and compartments. Loading compartments in a planned order and keeping weight within axle limits helps maintain steering and braking control on a tanker.

The maximum weight a single axle or axle group may carry under law. Overloading a tanker axle reduces braking and steering performance and can result in fines or being placed out of service.

Transferring product out of the tank at the destination. It requires setting the parking brake, chocking wheels, connecting grounding, opening valves in the correct order, and watching for leaks throughout.