New York CDL Tanker key terms

The front-to-back movement of liquid inside a partly filled tank when the vehicle speeds up, slows down, or changes gears. Surge pushes against the tank heads and shifts weight onto the tractor.

The empty space left above the liquid in a tank so the product can expand as it warms without overflowing. Outage is measured as a percentage of total tank volume.

An internal wall inside a tank that slows the back-and-forth movement of liquid. Baffles are not full bulkheads; some liquid still passes through openings, so surge is reduced but not eliminated.

A solid internal wall that divides a tank into separate compartments and completely blocks liquid from moving between them. Cargo is loaded and unloaded compartment by compartment.

A tank with no baffles or bulkheads inside, used for food-grade and other single-product loads. Liquid moves freely, so surge is strongest and the driver must brake and turn very gently.

One sealed section of a divided tank barrel, each with its own hatch and outlet. Loading compartments unevenly changes axle weights and can make the vehicle unstable.

The piping and valves that connect tank compartments to a single loading or unloading line. Setting manifold valves correctly prevents mixing products and cross-contamination between compartments.

A probe in each compartment that signals or automatically stops the flow when liquid reaches a set level during loading. It protects against overfilling and keeps the required outage space.

The combination of high-level sensors, alarms, and automatic shutoff devices that stop product flow before a compartment overflows. Drivers must confirm the system is working before starting a load.

A system that captures fuel vapors displaced from a tank and returns them to the storage facility instead of releasing them to the air. Lines and fittings must be connected and sealed properly.

The pressure a liquid's vapor exerts inside a closed tank, which rises as the product gets warmer. High vapor pressure means more fumes, greater fire risk, and more stress on tank seals.

Filling a tank through a connection at the lower part of each compartment rather than through the top hatch. It reduces static and vapor generation and lets overfill sensors work.

Filling a tank through an open hatch on top of the barrel. The driver must bond the vehicle, control the flow rate, and watch the level to avoid overfilling and static sparks.

Connecting the tank vehicle to the loading rack or receiving facility with a cable so both are at the same electrical potential. Bonding prevents a spark from jumping between them.

Connecting equipment to the earth so static charge drains away safely. Grounding plus bonding is required before loading flammable liquids and must stay connected through the whole transfer.

Electric charge that builds up when liquids flow or splash and when surfaces rub together. If it discharges as a spark near vapors, it can ignite them, so bonding and grounding are required.

A liquid with a flash point at or below 60 degrees Celsius (140 degrees Fahrenheit). Its vapors can ignite at ordinary temperatures, so it carries strict placarding, loading, and driving rules.

A liquid with a flash point above 60 degrees Celsius (140 degrees Fahrenheit). It is less easily ignited than a flammable liquid but still burns and is regulated when shipped in bulk.

The lowest temperature at which a liquid gives off enough vapor to ignite briefly when a flame is applied. It determines whether a product is classed as flammable or combustible.

The category assigned to a hazardous material under the DOT hazard classification system, such as Class 3 for flammable liquids. The class controls placards, shipping papers, and handling rules.

A diamond-shaped warning sign placed on the vehicle that shows the hazard class of the cargo. Placards must match the load and be removed or changed when the cargo changes.

The document that describes the hazardous material being carried, including proper shipping name, hazard class, quantity, and emergency contact. It must be within reach and shown to inspectors on request.

A reference carried in the cab that lists initial response steps for spills and fires by material or placard number. Drivers use it to give responders accurate information at the scene.

A valve that opens automatically to release pressure or vapor when it gets too high inside a tank. It protects the tank from rupture during loading, unloading, or fire exposure.

Allowing air or vapor to enter or leave a tank so pressure stays within safe limits during temperature changes or product transfer. Blocked vents can cause a tank to collapse or rupture.

A crash in which the vehicle tips onto its side or roof. Tank vehicles are top-heavy and roll over more easily, so drivers must slow down before curves and avoid sharp steering.

The point where the vehicle's weight is balanced. A loaded tank has a higher center of gravity than most trucks, so it tips more easily in turns and on ramps.

The movement of product to one side of a tank during a turn or lane change, which adds weight to the outside of the curve. It can tip the vehicle even at moderate speed.

Applying the brakes gradually and early so liquid does not slam forward into the tank head. Hard stops with a partly filled tank can push the vehicle forward and damage the tank.

The total distance needed to stop, including perception, reaction, and braking distance. A loaded tank vehicle needs much more room than a dry van, especially on wet or icy roads.

The gap kept behind the vehicle ahead. Tanker drivers should allow at least one second per ten feet of vehicle length plus extra space, and more in bad weather or heavy traffic.

Spreading the load so each axle stays within its legal limit. Loading compartments out of balance can overload an axle, reduce steering grip, and make the vehicle unsafe to drive.

The maximum weight allowed on a single axle or axle group under federal and state rules. Drivers must check scale tickets and load sheets to stay within these limits.

The condition of the tank shell, heads, seams, and fittings that keeps product inside. Drivers check for cracks, leaks, and damaged seals during pre-trip and after any hard contact.

The required check of the tank, valves, hoses, placards, and emergency equipment before driving. It catches leaks, loose fittings, and missing gear that could cause a spill or crash.

The equipment and steps used to keep a spilled product from spreading, such as absorbent, drip pans, and blocking drains. Quick containment reduces fire risk and environmental damage.

A liquid carried in a tank or other container with no intermediate packaging, such as a tanker barrel. Bulk shipments trigger specific placarding, shipping paper, and loading rules.

A tank built and cleaned to food-grade standards so products stay free of contamination. It is usually smooth bore and needs careful cleaning between different food products.