100+ Free Tankerman-Assistant LG Practice Questions

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2026 Statistics

Key Facts: Tankerman-Assistant LG Exam

50 questions

Q457 Exam Length

USCG NMC Q457 module

70%

Passing Score

USCG NMC

150 psi

Minimum Cargo Hose Rating

USCG tank vessel regulations

-260 F

LNG Carriage Temperature

Liquefied natural gas properties

Dec 2024

Tankerman Renamed Tank Vessel

USCG / 46 CFR Part 13

46 CFR 13

Governing Regulation

Certification of Tank Vessel Personnel

The USCG Tank Vessel-Assistant (Liquefied Gases) endorsement, formerly Tankerman-Assistant, lets a mariner assist with liquefied gas cargo transfers under a person in charge per 46 CFR Part 13. Candidates take NMC module Q457, a 50-question multiple-choice exam (code TK02) requiring 70% to pass. Content centers on liquefied gas properties and hazards (LNG boils near -260 F, LPG near -42 F, ammonia near -28 F, ethylene near -155 F; flammable ranges, flash point, autoignition, cryogenic cold burns, brittle fracture, BLEVE), cargo containment and transfer systems (tanks, secondary barriers, hoses rated to 150 psi, valves, vapor return, cool-down), atmosphere control and gas detection (inert gas, nitrogen for ammonia, combustible gas indicators, span-gas calibration), emergency and fire response (ESD, dry chemical, water spray, frostbite first aid), and transfer regulations under 33 CFR 155-156 including the Declaration of Inspection and pre-transfer conference. The credential was renamed in December 2024.

Sample Tankerman-Assistant LG Practice Questions

Try these sample questions to test your Tankerman-Assistant LG exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the primary hazard of liquefied petroleum gas (LPG) and liquefied natural gas (LNG)?

A.Temperature

B.Toxicity

C.Flammability

D.Pressure

Explanation: Although liquefied gases are also cold and stored under pressure, their primary hazard is flammability: vapor mixed with air within the flammable range ignites readily, so fire and explosion prevention drives nearly all gas-carrier safety practice.

2Which statement best describes a liquefied gas cargo?

A.A liquid that must be heated above ambient temperature to form a gas

B.A liquid that must be stored at absolute zero to remain liquid

C.A substance that at normal temperature and pressure would be a gas

D.A gas mixed with another substance that causes it to liquefy

Explanation: A liquefied gas is a substance that at ordinary atmospheric temperature and pressure is a gas; it is kept liquid for transport by refrigeration, pressure, or both, greatly reducing its volume.

3In what condition is LNG carried aboard a liquefied gas carrier?

A.At a pressure in excess of 15.4 psia

B.Entirely in the vapor stage

C.At its critical temperature

D.At its boiling point

Explanation: Fully refrigerated LNG is transported at its atmospheric boiling point, about -260 F (-162 C), at near-atmospheric pressure; boil-off vapor is continuously generated and is typically used as fuel or reliquefied.

4Compared to air, the vapors of liquefied petroleum gas (propane/butane) are:

A.Lighter than air

B.The same density as air

C.Heavier than air

D.Variable, sometimes lighter and sometimes heavier

Explanation: Propane and butane vapors have a vapor density greater than air (propane about 1.5 times air), so released LPG vapor sinks and collects in low spaces such as bilges, trenches, and decks, where it can travel to an ignition source.

5The flash point of a liquid is defined as the lowest temperature at which the liquid:

A.Will give off sufficient vapors to form a flammable mixture with air near its surface

B.Will burn steadily once ignited

C.Must reach before it will flow readily

D.Will explode without an ignition source

Explanation: Flash point is the lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near its surface; it is a fundamental measure used to classify flammable versus combustible liquids.

6Under U.S. regulations, flammable liquids are defined as liquids that:

A.Give off flammable vapors only above 80 F (27 C)

B.Have a Reid vapor pressure of 18 pounds or more

C.Give off flammable vapors at or below 80 F (27 C)

D.Sustain combustion at a temperature at or below 100 F (38 C)

Explanation: U.S. tank-vessel regulations classify a liquid as flammable when it has a flash point at or below 80 F (27 C); above that threshold and up to 150 F the liquid is termed combustible.

7Autoignition temperature is best described as the lowest temperature at which a flammable vapor will:

A.Form an ignitable mixture with air

B.Stop burning once a flame is removed

C.Ignite and sustain combustion without a spark or flame

D.Condense back to a liquid

Explanation: Autoignition temperature is the lowest temperature at which a vapor-air mixture ignites spontaneously and burns without any external spark or flame; for example, methane autoignites near 1000 F (about 537 C).

8The approximate flammable (explosive) range of methane in air is:

A.About 1 to 9 percent by volume

B.About 16 to 25 percent by volume

C.About 2.5 to 34 percent by volume

D.About 5 to 15 percent by volume

Explanation: Methane, the main component of LNG, has a flammable range of roughly 5 to 15 percent by volume in air; mixtures below the lower limit are too lean and above the upper limit too rich to burn.

9Ethylene has an unusually wide flammable range. Approximately what is that range in air?

A.2.5 to 34 percent by volume

B.2.1 to 9.5 percent by volume

C.5 to 15 percent by volume

D.16 to 25 percent by volume

Explanation: Ethylene's flammable range is approximately 2.5 to 34 percent by volume in air, much wider than methane or propane, making it ignitable over a broad mixture range and requiring tight atmosphere control.

10What is the approximate atmospheric boiling point of fully refrigerated ammonia (NH3) cargo?

A.-42 F (-41 C)

B.-260 F (-162 C)

C.-155 F (-104 C)

D.-28 F (-33 C)

Explanation: Anhydrous ammonia boils at about -28 F (-33 C) at atmospheric pressure, so fully refrigerated ammonia is carried near that temperature; it can also be carried under pressure at ambient temperature.

About the Tankerman-Assistant LG Exam

The USCG Tank Vessel-Assistant (Liquefied Gases) endorsement, renamed from Tankerman-Assistant in December 2024, authorizes a mariner to assist with liquefied gas cargo transfers under the supervision of a person in charge. The credential is governed by 46 CFR Part 13, and the knowledge examination is NMC module Q457 (Tankship Liquefied Gases), a 50-question multiple-choice test requiring a 70% passing score. The exam shares much of its content with the Dangerous Liquids module but adds a cargo-properties block specific to liquefied gases such as LNG, LPG, ammonia, and ethylene.

Questions

50 scored questions

Time Limit

Set by the NMC examination module

Passing Score

70% (35 of 50)

Exam Fee

MMC application/evaluation fees apply; confirm on the NMC website (U.S. Coast Guard National Maritime Center (NMC))

Tankerman-Assistant LG Exam Content Outline

22%

Liquefied Gas Properties & Hazards

Boiling points and vapor density of LNG (about -260 F), LPG/propane (about -42 F), ammonia (about -28 F) and ethylene (about -155 F); flammable range (LEL/UEL), flash point and autoignition; cryogenic cold burns, brittle fracture of carbon steel, BLEVE, and visible vapor-cloud behavior

18%

Cargo Containment & Transfer Systems

Independent (Type A/B) and pressure-vessel (Type C) tanks, secondary barriers and hold spaces, cargo piping and crossovers, hose rated to at least 150 psi, valve seating, pump relief valves, controlled cool-down, vapor return, and filling limits that allow for thermal expansion

16%

Atmosphere Control & Gas Detection

Inert gas to keep oxygen below combustion levels, nitrogen padding for ammonia to avoid carbamate formation, purging and gassing-up to avoid the flammable range, combustible gas indicators and their limits, span-gas calibration, oxygen analyzers, and enclosed-space entry testing

16%

Emergency, Fire & First Aid

Emergency shutdown (ESD) and emergency release couplings, shutting off the leak first in a gas fire, dry chemical and water-spray tactics, cooling exposed steel to prevent BLEVE, rewarming frostbite at about 108 F, and restoring breathing in gas-poisoning casualties

16%

Regulations, PIC & Documentation

46 CFR Part 13 tankerman endorsements and the assistant's supervised role, 33 CFR 155-156 transfer rules, the Declaration of Inspection signed by each person in charge, the pre-transfer conference, the all-round red light transfer signal, and Certificate of Inspection authorized cargoes

12%

Pollution Prevention & Stability

Topping-off as the critical bunkering moment, plugging scuppers to contain deck spills, loading as the most frequent pollution source, list control with wing tanks and trim control by shifting weight, sloshing/free-surface limits, static control, and vacuum protection of tanks

How to Pass the Tankerman-Assistant LG Exam

What You Need to Know

Passing score: 70% (35 of 50)
Exam length: 50 questions
Time limit: Set by the NMC examination module
Exam fee: MMC application/evaluation fees apply; confirm on the NMC website

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

Tankerman-Assistant LG Study Tips from Top Performers

1Memorize key cargo boiling points: LNG near -260 F (-162 C), ethylene near -155 F (-104 C), propane near -42 F, and ammonia near -28 F (-33 C), and know that LPG vapor is heavier than air

2Learn each flammable range: methane about 5-15%, propane about 2-9.5%, ethylene about 2.5-34%, and ammonia about 16-25%, and remember flammability is the primary hazard of LPG and LNG

3Know that an inert gas system works by reducing oxygen below the level needed for combustion, and that ammonia is inerted with nitrogen because it reacts with CO2 to form solid carbamate

4Understand why a combustible gas indicator reads low when the hydrocarbon level is above the upper explosive limit (too little oxygen to burn the sample on the filament)

5Remember the transfer rules: each person in charge signs the Declaration of Inspection (33 CFR 156), cargo hose must withstand at least 150 psi, and an all-round red light signals a flammable cargo transfer

6Drill emergency response: shut off the leak first in a gas fire, treat frostbite by rewarming in water at about 108 F, and restore breathing first when treating gas-poisoning casualties

Frequently Asked Questions

What is the USCG Tank Vessel-Assistant (Liquefied Gases) endorsement?

It is a U.S. Coast Guard merchant mariner credential endorsement, formerly called Tankerman-Assistant, that authorizes the holder to assist with liquefied gas cargo transfers under the supervision of a person in charge, as governed by 46 CFR Part 13.

How many questions are on the Q457 exam and what score do I need?

The NMC Q457 (Tankship Liquefied Gases) module has 50 multiple-choice questions, and you must answer at least 70% (35 of 50) correctly to pass.

What cargoes does the liquefied gas exam cover?

It covers liquefied gases such as LNG (methane), LPG (propane and butane), ammonia, and ethylene, including their boiling points, vapor densities, flammable ranges, toxicity (notably ammonia), and cryogenic hazards.

Why was the credential renamed in 2024?

In December 2024 the Coast Guard updated tank vessel personnel terminology, renaming the Tankerman-Assistant endorsement to Tank Vessel-Assistant; the underlying 46 CFR Part 13 requirements and Q457 exam content remain the focus.

What is the difference between the Assistant and the PIC endorsement?

An Assistant (Tank Vessel-Assistant) helps with cargo transfers under supervision, while a Person-in-Charge (Tank Vessel-PIC) is qualified to supervise and be in charge of the transfer. The Assistant endorsement is often a step toward the PIC endorsement.

What is the Declaration of Inspection?

Under 33 CFR 156, the Declaration of Inspection is the form that each person in charge must complete and sign before an oil or hazardous materials transfer begins, confirming the vessel, equipment, and procedures are ready and safe.

What is span gas used for on a gas carrier?

Span gas is a known reference concentration used to calibrate gas analyzers and detectors so they indicate correct gas concentrations, which is essential for reliable atmosphere monitoring and leak detection.

100+ Free Tankerman-Assistant LG Practice Questions

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