Hot Work Procedures Flashcards
7 cards from real CMC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hot Work Procedures flashcards as text
A Marine Chemist is testing a freshly cleaned cargo tank that previously carried crude oil. A reading of 8% LEL is obtained at the bottom. What should the chemist do?
Answer: Require additional ventilation until readings are consistently below acceptable limits throughout the space
Although 8% LEL is below 10%, prudent practice requires continued ventilation until readings are well below 10% LEL uniformly, as vapor levels can fluctuate.
Which regulatory body sets the primary U.S. requirements for Marine Chemist certification of vessels before hot work?
Answer: U.S. Coast Guard via 46 CFR
The U.S. Coast Guard under 46 CFR Part 35 (and related sections) mandates Marine Chemist inspection of vessels before hot work in hazardous areas.
In marine hot work practice, what does the term 'inerting' refer to?
Answer: Replacing the atmosphere in a tank with inert gas to eliminate oxygen and prevent combustion
Inerting replaces the tank atmosphere with inert gas (typically nitrogen or flue gas) to reduce oxygen below the level needed to support combustion.
A Marine Chemist finds that a tank has an oxygen concentration of 19.0% and 0% LEL. Can the tank be certified for hot work?
Answer: No, because oxygen below 20.9% may indicate contamination from inert gas making re-gas-freeing necessary
An oxygen level of 19.0% suggests residual inert gas that could displace oxygen further; the space must be fully gas-freed to near-atmospheric oxygen before hot work is authorized.
What is the primary purpose of a 'fire watch' during hot work operations on a vessel?
Answer: To monitor for fire ignition, smoldering, or sparks in the work area and adjacent spaces, and to sound an alarm if needed
The fire watch is dedicated to observing for signs of fire or ignition in the work area and surrounding spaces and initiating emergency response immediately.
When hot work is conducted on the outer hull plating of a vessel, which internal space presents the greatest concern for the Marine Chemist?
Answer: Any void space, ballast tank, or cargo tank immediately behind the hull plating being worked on
Heat and sparks from hull plating work can penetrate into immediately adjacent internal spaces, which must be tested and confirmed free of flammable vapors.
A shipyard worker claims that because a tank has been water-washed, a Marine Chemist certificate is unnecessary for hot work. This claim is:
Answer: Incorrect, because water washing alone does not guarantee the absence of flammable vapors or toxic gases
Water washing reduces residues but does not guarantee gas-free conditions; atmospheric testing by a Marine Chemist is always required before hot work regardless of washing.