Transport Guidance for Steel Cargoes

American Club: Transport Guidance for Steel Cargoes
67
(2)
Temperature control system. A temperature control system of circulating air within
insulated cargo hold.
(3)
Mechanical ventilation. The principle of most types of shipboard mechanical ventilation is to
replace the warm air in the cargo hold with colder ambient air.
6.7.2
For voyages from warmer to colder climatic regions, natural ventilation may be insufficient for the
carriage of steel. Vessels carrying steel cargoes should be equipped with a proper functioning
mechanical ventilation system with sufficient capacity of between 15 – 25 air changes per hour
(calculated under the assumption that the cargo hold is empty). Furthermore, all fans need to be checked
to ensure that they run properly in the correct direction. Where the vessel is not fitted with fixed
mechanical ventilation, the vessel owner may then consider supplying and using portable blowers,
if necessary.
 
6.8 Ventilation of steel cargoes
6.8.1
It is important to note again that the goal of ventilation is not to cool or heat the cargo. Ventilating
dissipates the natural buildup of water vapor to minimize the differences in temperature between the
air in the hold and vessel’s steel structure to prevent condensation build up on the vessel’s steel
parts in the cargo hold.
6.8.2
The periphery of the cargo stowed is directly influenced by the passing of the cooler ventilation air,
will become cooler as well. This process also reduces the difference in temperature between the
cargo and vessel’s steel structure. Consequently, the periphery of the stowed cargo becomes dryer
and cooler resulting in moisture migration from the center towards the boundary of the stowed cargo.
It should be noted that the efficiency of mechanical ventilation does not always consistently ventilate
throughout a loaded cargo hold. This should be taken into consideration, particularly if mechanical
ventilation is applied.
6.8.3
When the weather conditions and the dew point are within acceptable parameters to ventilate, the
hatches can be opened during the voyage to allow appropriate surface cooling but only when sea
conditions are sufficiently benign. If possible, this type of ventilation should also be carried out in
port until completion of cargo loading or discharging.
6.8.4
During periods of inclement weather, steps should be taken to prevent rain and spray from entering
the cargo spaces. This may include, if necessary, suspending ventilation until conditions improve.
However, during rain or fog, ventilation can be continued as long as the dew point temperature of
the ambient air is lower than the dew point temperature of the air inside the hold. Any such
conditions and actions taken should be recorded in the Deck Log Book and in the “Remarks” section
of the Humidity-Temperature-Cargo Ventilation Record Book (see Section 6.9.1(2)).

American Club: Transport Guidance for Steel Cargoes
68
6.8.5
Ventilation can be done at night if the readings indicate that ventilation is appropriate bearing in
mind that ambient temperatures are usually lower at night. Therefore, the risk of developing ship
sweat is more likely during the hours of darkness so ventilation may be continued if conditions
permit. If ventilating at night, the crew should be particularly diligent at monitoring the weather
conditions as set forth in Section 7.2.1.
6.8.6
In addition to ventilating the cargo holds, it is important that cargo holds inspections are regularly
made, preferably as often as once a day. This need not necessarily involve direct entry into the cargo
holds. For example, ship sweat may be seen forming on the underside of manhole covers. In such
instances, and especially at night, the cargo should be ventilated irrespective of the ”Dew Point Rule”
or “3º Celsius Rule” (see Section 6.6), weather permitting.
6.8.7
Vessels with natural ventilation systems should be equipped with either permanent or portable cargo
hold dehumidification systems that are able to remove the moisture from the holds before any
condensation should occur. Additional dehumidifiers should be considered if the vessel is carrying a
high value steel cargo such as steel coils or other finished steel cargoes.

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