a) Efficient refrigeration machinery and good insulation of the compartment.
b) Careful preparation of the compartment including cleaning, dunnaging and precooling. c) Effective system for monitoring and maintaining specified temperature during loading, transportation and discharging.
d) Segregation of cargo.
e)
Monitoring and control of CO2concentration in the compartment, and good ventilation.
Precautions Relating To
Transportation Of
Refrigeration Cargoes
A) Refrigeration Machinery
1) Refrigeration machinery should be checked and tested. Brine pipes should be tested to a pressure 1½ times their normal working pressure to check for any possible leaks. A close inspection must also be made of all insulation and defects rectified. Insulated ventilator plugs must be closely fitted in place and sealed with saw dust.
2) Scuppers and other water drainage system around and near refrigeration machinery must be checked to ensure that moisture will have an easy and free access to the bilges.
3)
Test CO2 extraction, generation andinjection equipment.
B) Preparation Of Compartment
1) Sweep and clean thoroughly with particular attention to brine pipes, insulation, bins, gratings, air ducts in order to remove all traces, stains and odour of previous cargo. After cleaning these should be wiped down with a disinfectant fluid to prevent formation of mould there on.
2) Bilges should be made dry, cleaned and ventilated in order to remove foreign matter and odour. Brine traps should be checked and topped up to prevent cold air from entering the bilges and freezing them or odour from reaching the refrigerated compartment.
3) Strum boxes should be cleared and bilge suction tested.
4) Clean dunnage, likely to be used, meat hooks, bars chains or any other equipment or appliances to be used for loading or stowage of cargo should be placed in the compartment after they have been cleaned and sterilised. 5) Thermometers should be tested and kept ready and thermometer pipes, if removed, should be fitted, or extended to enable recording of temperatures at the top, middle and lower levels of the compartments.
6) Portable trunks in holds of battery compartments must be assembled in place. 7) The compartment should be pre-cooled to a temperature lower than the normal carrying temperature, to allow for fluctuations during loading, 24/48 hours before commencement of loading.
8)
If lead, copper or tin ingots are also loaded in refrigerated compartments, additional pre- cooling is necessary. Chilled compartments should be maintained at their transit temperature and frozen compartments at 14oFfor 6 hours for each floor tier of ingots. 9) Approximate pre-cooling temperatures: -
Frozen compartments 10oF
Chilled compartments 22oF
Apples, pears, peaches and grapes 28oF
Oranges, lemon, grape fruit 36oF
Cheese 40oF
10) The pre-cooled compartment should be inspected by the appointed surveyor and certified ‘fit to load’ before loading can commence.
C) Loading, Discharging, Handling
1) Dunnaging should be so arranged so as to: -
a) provide adequate support to the cargo, b) ensure sufficient clearance from deck and sides to prevent contact between cargo and the cooling pipes, air ducts, baffle plates and any water likely to condense in the compartment,
c) in the event of different temperatures being maintained in adjoining compartments liberal use should be made of saw dust on deck dunnage on the sides and drip trays under deck head to prevent water contamination in the warmer compartment,
d) to prevent damage to bottom tiers by over stowed cargo,
e) to permit unobstructed circulation of cooled air below, around and through the cargo including dunnaging at intermediate tiers for cargo of tight block stow type so that uniform temperature can be maintained throughout the compartment.
2) Cargo tendered for shipment should be inspected thoroughly: -
a) frozen cargo should be hard frozen and free of spots or mould. There should be no blood stains on the wrappings,
b) fruit should not be in advanced stated of ripeness, skin should not be discoloured and should not be brown on the inside. Random samples should be taken and cut open.
3) Cooling in compartment opened for loading should be stopped to prevent frosting of grid pipes which will not only reduce cooling
efficiency but on melting will result in water accumulation in the compartment and possible damage to cargo there in. Any snow formation on pipes should be carefully swept off.
4) Compartments not being worked should be kept closed. If necessary to keep them open to permit loading in adjoining hold or space, escape of cold air should be prevented by rigging tarpaulin screens or some similar device. Air screens may be fitted on some ships.
5) Monitor temperature in the compartment during loading and should it rise above the specified level, close the compartment and re- cool it.
6) No walling should be permitted on cases of fruit, eggs or cheese as they are fragile Over other frozen cargo, shoes should be covered with clean gunny sacking or similar material. 7) Cargo should not be dragged, pushed or thrown. Slings should be made in the hatch square.
8) Proper cargo gear should be used e.g. canvas nets for meat and trays for crates/cases of cheese, butter, eggs and fruit. 9) Heavy meat should not be stowed over light meat.
10) Taintable cargo should not be stowed with fruit nor loaded in a compartment which has carried fruit unless it has been de-odourised. 11) Thick paper should be pasted over joints to prevent air leak.
D) During Voyage
1) Monitor and record temperature in all compartments and ensure that it is maintained at the desired level.
2)
Monitor CO2 concentration incompartments carrying fruit and arrange extraction to ensure that it does not exceed 5%.
3)
In compartments containing meat CO2 maybe injected upto 6 kg per 1000 cubic feet to help pressure it for a longer time.
4) For chilled meat ventilation should be arranged to achieve complete air change 20- 25 times every hour.
CO
2Control
1)
Ripening of fruit generates heat and CO2which must be removed to preserve the cargo. Maximum permitted concentration is 5%.
2)
Presence of CO2 helps preserve meat for alonger time and CO2 should be injected into
the compartment loaded with meat, if necessary, upto 10% concentration.
3)
CO2 concentration should be checked andrecorded at least once daily, but preferably once every watch at sea.
4)
In the past litmus paper cartridge was used to determine CO2 concentration by lowering itinto the hold. Its degree of discolouration indicated CO2 concentration.
5)
Modern method is thermoscope in which a sample of air is drawn from the hold and allowed to mix with caustic soda. This generates heat which, when measured, indicates CO2 concentration.Containers
A considerable amount of refrigerated cargo is carried in containers. These are of two types: -
Reefers
containers with an independent electrical
or diesel driven refrigeration system.
portholes which depend on external source
for cooling.
Advantages of using
containers are
no contamination or tainting no stacking damage no condensation damage no insulation required in ships’ cargo
space.