Cargo Tank Cleaning Procedures & Residue Management Flashcards
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When determining a tank cleaning procedure for a chemical tanker, which document serves as the primary operational reference for cargo-specific cleaning requirements and compatibility?
Answer: The Chemical Data Guide or the tanker company's proprietary tank cleaning guide
The Chemical Data Guide (e.g., Witherby's) or a tanker company's tank cleaning guide provides cargo-by-cargo cleaning sequences, compatibility matrices, and wall wash criteria.
Why is a cargo's miscibility with water an important consideration in planning tank cleaning operations?
Answer: It determines whether water washing is effective or if alternative solvents are needed first
Water-miscible cargoes dissolve in wash water and are effectively removed by water washing, while water-immiscible cargoes require a compatible solvent pre-flush before water washing can be effective.
During hot-water tank washing operations, what is the primary atmospheric hazard that increases compared to cold-water washing?
Answer: Enhanced volatilization of cargo residues, potentially intensifying flammable or toxic vapor generation
Elevated water temperature increases the vapor pressure of cargo residues, generating more vapors and potentially creating or worsening a flammable or toxic atmosphere during washing.
What is 'wall wash testing' used for in chemical tanker operations?
Answer: Verifying that a tank has been adequately cleaned so the next cargo will not be contaminated
Wall wash testing involves wiping a solvent across cleaned tank surfaces and analyzing the solution to confirm residue levels are below limits that would contaminate the next cargo.
Which agency enforces MARPOL Annex II cargo tank cleaning and discharge requirements for chemical tankers operating in United States waters?
Answer: The United States Coast Guard (USCG)
The USCG is the primary federal agency responsible for enforcing MARPOL requirements, including Annex II cargo tank cleaning and washings discharge rules, in US waters.
What is the Marine Chemist's specific role with respect to cargo tank residue conditions before personnel may enter for cleaning?
Answer: To test the tank atmosphere and issue certification that conditions are safe for personnel entry
A Marine Chemist evaluates the tank atmosphere for oxygen content, flammability, and toxicity, then certifies whether conditions meet safety requirements for personnel entry under NFPA 306.
When a tank survey reveals that residue from a previous cargo is chemically reactive with the intended next cargo, what is the required course of action?
Answer: Perform additional cleaning until the tank is certified free of reactive residue
Reactive cargo residues pose serious chemical reaction, fire, and explosion hazards; additional cleaning must be performed until the tank is certified safe for the next cargo.