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Chilled and Frozen Reefer Cargo Defrosting Guideline

Chilled Cargo: Is the Cargo which preset temperature exceeds 0-degree Centigrade and is not frozen. To maintain freshness, such as fruits, vegetables, etc., chilled transportation is increasingly used by freight transporters. It is required not only for perishable foods but also for photographic film and chemicals, which dislike high temperatures. To prevent damage during transit, advanced knowledge about temperature control is critical.

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Frozen Cargo: Needs temperature setting less than 0-degree Centigrade. Frozen fish, meat, etc. are examples of such categories.

During the refrigeration unit operation, a layer of ice will form on the evaporator coils depending on the temperature set, the temperature of the Cargo, the amount of fresh air ventilation, and the cargo humidity.

The unit periodically enters a phase where heat is produced by a series of electrical bars, allowing defrosting to take place. At such times, all fans are turned off automatically to prevent heat from entering the cargo compartment. However, the return air temperature sensor is closely located to the refrigeration machinery that the temperature record will inevitably register some of this rise.

The record will, therefore, display periodic temperature increases in keeping with the defrost periods. It must be stressed that these increases, which are conspicuous on paper chart recorders, have no immediate effect on the actual temperature of the Cargo and are not an indication of an unstable refrigeration unit.

Electronic loggers usually indicate the timing and duration of defrosting periods in addition to temperatures.

If Cargo is loaded into a container in a "Warm" or Hot condition exceeding the specified temperature, the refrigeration unit will automatically work to bring the cargo temperature down towards the correct level.
This unintentional strain on the unit may result in a heavier accretion of ice on the evaporator coils, leading to an increase in the defrost patterns recorded.

Recorder charts do not identify refrigeration unit defects but do give useful indications of correct operation. Data logger records may give detailed information about system faults in addition to Setpoint, delivery, and return air temperatures. Container temperature recording systems do not usually record actual cargo temperature, only air temperatures, but shippers loggers within the stow may record cargo temperature.
Reefer Container
Fig :Reefer Container

Related articles

Reefer cargo Handling In Port
Reefer containers shall be plugged in and supplied with ships power as soon as practicable after loading. In case it is to be done by shore hands, ships crew shall still closely monitor the operation and confirm that all reefer containers are supplied with power earliest after loading....

Reefer cargo care at sea
At sea, all reefer containers shall be monitored by checking physically at least Twice daily (weather permitting). All monitored data for each reefer container on board shall be entered in a reefer monitoring log and retained for 3 years. Some reefer containers with special cargo (e.g.: VIP cargo) come with instructions for more frequent monitoring and reporting. Such instructions shall be strictly followed. ....

Commodities Shipped In Reefer Containers
Some cargoes may require controlled humidity (e.g. flower bulbs). It should be remembered in such cases that many refrigeration units are only capable of reducing humidity within the cargo space and the settings should be applied accordingly. ....

Reefer Cargo Temperature Recording
A Partlow recorder registers temperature on a pressure sensitive circular chart over 31 day period. If the voyage transit is expected to exceed 31 days, care must be taken to ensure charts are replaced before expiry. The first chart should be placed under-neath the new chart in order to build up a complete temperature record for the entire voyage up until arrival at the final destination. .....

Reefer Cargo Maintaining Records
Monitoring the digital & chart temperatures of all reefer containers at least twice a day. Daily reefer container temperature check lists should be maintained, and printouts from monitoring unit should be preserved.....

Reefer Cargo Defrosting
During the operation of a refrigeration unit, a layer of ice will form on the evaporator coils depending on the temperature set, the temperature of the cargo, the amount of fresh air ventilation and the cargo humidity. The unit periodically enters a phase where heat is produced by a series of electrical bars, allowing defrosting to take place. At such times, all fans are turned off automatically in order to prevent heat from entering the cargo compartment. ....

Basic check item prior stowing Reefer Cargo
Stowage location of reefers must be checked against vessels reefer receptacle locations. In case reefer containers must be loaded in irregular locations, it must be confirmed that monitoring and repair will be possible during the voyage and that vessel has sufficient extension cables for providing power. ....

Container handling more info pages:

  1. Containership advantages

  2. Containership cargo stowage and planning

  3. Procedures and guidelines for dangerous cargo handling

  4. How to avoid irregular stowage of containers ?

  5. Measures against lashing failure

  6. Reefer container stowage guideline

  7. Care of Reefer container during sea passage

  8. Container ships procedures for securing for sea

  9. Deployment and monitoring of moorings and safety of crew

  10. Cargo securing procedure for container ship

Confirmation and record of securing

The following checklists shall be used to confirm the securing condition:

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Checklist for Navigation in Heavy weather

Checklist for Departure

How to maintain Water tightness, Seaworthiness, Fire integrity and Security of ship ?

Securing your vessel for sea passage - when to check and what to check

Confirming stability & hull strength prior sailing

Collecting Information and Data for Passage Planning

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