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Gard Guidance Masters VENTILATION

For further details please refer to Gard News 173, Don’t work up a sweat.

Whilst the principles and knowledge of proper ventilation should have been part of the Master’s and officers’ education and training, damage to cargo often arises as a result of improper ventilation. Care is required when ventilating to avoid two main problems
  • ship sweat
  • cargo sweat.

    Ship sweat occurs when air within the hold is cooled by the vessel’s structure and occurs mainly on voyages from warmer to colder climates. If sufficient air space is left in the cargo hold, condensation can occur and ship’s sweat may drip onto the surface of the cargo.

    Cargo sweat occurs when air within the hold is cooled by the cargo and occurs mainly on voyages from colder to warmer climates. If the ventilating air flowing over the cargo has a higher temperature than the cargo itself, the air will be cooled and may condense on the cooler surface of the cargo.

    Whether surface or through ventilation is required, depends upon
  • the nature of the cargo and its packing
  • climate changes during the voyage
  • sea conditions.

    Ventilation should only be carried out when the dew point of the ambient air is lower than the dew point of the hold air.

    Cargoes fumigated before loading cannot be ventilated immediately and in some circumstances, e.g. heavy weather or humid ambient conditions preventing ventilation, some ship’s sweat may be unavoidable. Cargoes with a high moisture content will also suffer from moisture migration. In view of this, proper and effective stowage is essential to prevent the cargo from coming into contact with moisture.

    The Master is advised
  • to obtain instructions from the shipper as to the proper ventilation requirements for certain types of cargoes to be loaded
  • to refer to any reference books.

    Accurate temperature and ventilation records must be kept when there is ventilation of the cargo to defend the Company should a claim be lodged. The inspection of the cargo spaces must be recorded as well, with dates and times when this was undertaken.