QUESTION 12.4.1

Cargo and ballast-system operability in sub-zero temperatures

Oil, Chemical, LPG, LNGCargo Control Room, Pumproom, Compressor Room, Main Deck

What is being checked

The inspector is checking whether cargo, ballast, inert-gas, venting, hydraulic and pollution-prevention systems are drained, heated, protected and periodically operated so that freezing cannot disable transfer, containment, pressure control or emergency shutdown.

Ready onboard

0/7 complete

SYSTEM MAPIdentify every exposed cargo, COW, ballast, inert-gas, vapour, drain, instrument-air and hydraulic component susceptible to retained water or low-temperature failure.DRAININGDrain deck lines, valves, heaters, drip trays, air lines, monitors and unused steam services from effective low points after testing or use.VENTINGKeep P/V valves, flame screens, mast riser, ballast vents and the P/V breaker protected and operable; remove covers that would obstruct required venting before transfer.HEATINGVerify deck-seal heating, cargo-compressor protection, antifreeze levels and ballast-tank heating or bubbling arrangements where fitted.HYDRAULICSStart power packs early, use suitable fluid and cycle cargo, COW and ballast valves at the defined interval to prevent freezing or blockage.BALLAST CONTROLCheck ballast-water salinity, freezing margin, tank condition and any required exchange or heating plan.OPERATION RECORDRecord pre-use line integrity tests, periodic cold-weather checks and final draining or restoration after cargo operations.

Practice questions

Answer aloud, then open the preparation point.

1Which cargo-system sections can retain water after draining?

Trace low points, valve cavities, pressure gauges, sample points, heaters, drip trays and dead legs rather than treating an open drain as proof that the whole line is dry.

2How is tank pressure protection kept available?

Inspect P/V valves, flame screens, the mast riser and P/V breaker, verify heat or antifreeze as fitted and remove any protective cover before the device is required.

3What is the ballast-water freezing margin?

Use measured salinity and expected water or air temperature to assess freezing risk and apply the vessel's exchange, heating or bubbling procedure.

4Why are hydraulic valves cycled during cold exposure?

Periodic movement and warmed suitable fluid reduce freezing and sticking risk, but the operation must respect cargo status and avoid an unintended valve movement.

5How is the inert-gas deck seal protected?

Show the heating arrangement, temperature or circulation check, water-level control and repeated verification during cargo operations.

6What must be checked after cargo completion?

Drain applicable lines and equipment, restore vents and valves, remove temporary covers where necessary and record any frozen or slow component for repair.

Where an observation may arise

TRAPPED LIQUID

Cargo, COW, ballast, monitoring or steam equipment retained water and froze because low points or valve cavities were overlooked.

VENT OBSTRUCTED

A canvas cover, snow or ice restricted a P/V valve, flame screen, mast riser or ballast-tank vent during operation.

DECK SEAL HEATING

The inert-gas deck-seal heating arrangement was unavailable or its operation was not checked.

WRONG ANTIFREEZE

The P/V breaker, stripping vacuum pump or other protected system had an incorrect concentration, level or temperature rating.

HYDRAULIC DELAY

Cargo pumps or valve hydraulics were started too late or not periodically exercised, leaving equipment unavailable when required.

BALLAST FREEZING RISK

Ballast salinity and temperature were not assessed or fitted heating and bubbling arrangements were started too late.

NO OPERATIONAL RECORD

The vessel could not demonstrate pre-use integrity, periodic cold checks or post-operation draining.

Master's practical note

Walk the cargo system by drainage path. The most credible checklist identifies each low point and who verified it; a single statement that all deck lines were drained is too weak.

Equipment boundary and references

Equipment boundary: Apply only to systems fitted and to the vessel's declared ice, winterisation, Polar Ship Certificate or routine sub-zero exposure. Protective covers must never compromise required pressure relief or ballast-tank venting.

References

OCIMF SIRE 2.0 Question Library Part 2, Version 1.0, Question 12.4.1
IMO Polar Code, Part I-A Chapters 4 and 6
IMO IGC Code where applicable
OCIMF The Use of Large Tankers in Seasonal First-Year Ice and Severe Sub-Zero Conditions
OCIMF ISGOTT

Last reviewed: 2026-09-12