Reefer vessels - caring for cargo
Introduction and general information
Most specialized reefer vessels are fitted with a vertical airflow system whereby the refrigerated air from the cooling batteries is introduced into the compartment under the floor gratings and vertically forced through the cargo via the holed gratings or spaced floor boards. The air flows back along the ceiling towards the return air openings of the cooler rooms and to the suction side of the reefer fans. This in order to pass the cooling batteries again.
Depending on the cargo, the cargo compartments are to be ventilated with fresh outside air in order to remove respiration gases like CO2 and ethylene produced by the cargo. It should be considered that foodstuffs are being carried and that these vessels are an important part in the transport chain from producers to consumers so that good hygiene is of paramount importance.
The following information is based on our long standing experience with cargo claims on reefer vessels but the information is not exhaustive.
It goes without saying that the reefer installation must be properly maintained. This also applies for the auxiliary engines and the generators so that at all times the capacity is sufficient to cope with the electric power demands of the reefer installation.
The reefer circulation fans, evaporators, fresh air fans and all other equipment, such as for instance air temperature sensors etc. and monitoring equipment are to be kept in a good working order. Regular testing and calibrating of the equipment is essential, including keeping a good record of all of this.
The insulation itself and the panelling that covers the insulation should be kept in a good condition and damage has to be repaired immediately.
Sufficient spare parts should be available on board the vessel. The maker's requirements for the quantity of the spare parts is to be considered as the minimum. Sufficient refrigerant to compensate for possible leakage of the system should be on board as well.
A preventive maintenance system is required to keep the installation and equipment in a good working condition.
Condition of cargo compartments prior to loading
After discharge of the previous cargo, cleaning of the cargo compartments is depending on the cargo which was carried. If it is concerning dry cargo, broom sweeping may be sufficient. All floor gratings have to be lifted and the debris and cargo remains gathered on the floor removed.
If it concerns a wet/dirty cargo like frozen tuna fish in bulk, the cargo compartments have to be washed with a high pressure cleaner. An appropriate fat/odour removing detergent can be applied.
Washing of the cargo compartments, also in case when only dry cargoes are carried, is required at times. Especially when cargoes of cars/trucks are carried in the cargo compartments on return voyages.
The drains of the tween decks and the bilges are to be checked, cleaned and made dry.
The condition of the hydraulic hoses of the tween decks should be visually checked for damage on a regular basis and pressure tested, at least annually. These hoses should not be painted in order to avoid that the material is affected by the solvents of the paint.
On reefer vessels, all air pipes of double bottom fuel oil and ballast tanks are hidden in and covered by the insulation and therefore not directly visible for a condition/tightness check.
The tightness of the manhole openings of the double bottom tanks can be checked by lifting the insulation plugs on these openings under the gratings. The emission of gases from fuel oil may result in a substantial cargo claim. In that respect one has to prevent that these gases, ex. vent pipe outlet on deck, find a way to enter the fresh air inlet.
Another issue is water or oil (if leakage of a fuel tank is involved) into the insulation material. The tight connection of the insulation material (polyester cover layer) with the construction around the double bottom tank manholes and in other locations may be affected.
The gratings or floor boards has to be checked and repaired, if necessary, in order to allow unobstructed use by forklift trucks. Spare material to allow for immediate repairs should be available on board the vessel.
The air channels below the gratings must be free and unobstructed as to allow an airflow from the cooler rooms to the opposite side of the compartment.
The vertical side boards in the compartments with sloping and/or tapered sides should be in a good order and condition and able to withstand the horizontal forces exerted on these by the cargo during rolling conditions.
The cargo compartments have to be pre-cooled in accordance with the prescribed carrying temperature of the cargo to be loaded. With regard to odours it should be noted that freezing temperatures may mask the presence of it.
Furthermore, the cargo compartments must be free from loose paint blisters and loose rust scaling.
The cargo hold lights, preferably fitted in a recess in the overhead panelling, need to be provided with protection so as to avoid contact with for instance a forklift truck as damaged parts may contaminate the cargo.
The rubber packing and closing arrangements of the weather deck hatch covers and hold access openings should be kept in a good condition to avoid (sea) water ingress.
Weather tightness tests, hose testing or ultrasonic testing, are to be done at times to ensure that the hatches are weather tight.
The air sealing rubber packing of the weather deck and tween deck hatch covers should be kept in a good condition as well.
The carrying instructions should be in plain language and clearly indicate whether the temperatures are in Celsius or in Fahrenheit. If the instructions are provided in a sort of code (like the Perishable Products Export Control Board (PPECB) instructions), the codes should be accompanied by a clear explanation.
Shipper's instructions may refer to specific cooling operations during loading, but it should always be taken into account that the supply from shore can be irregular and therefore a pre-loading meeting and a good communication with the shore is of utmost importance. For instance during long waiting times, it is to be considered to cover open spaces in order to guide the cooled air circulation through the already loaded cargoes.
Written carriage instructions should be issued by the cargo interests and in case of doubt these are to be clarified. In case the instructions are not clear, these are not to be accepted and a letter of protest should be issued.
Instructions like "temperature to be maintained at a ... °C." are too vague, as the instructions should mention the prescribed delivery air temperature, as this is the only temperature that can be properly adjusted with the reefer installation.
Instructions may also describe a certain level of relative humidity to be kept, but when this cannot be influenced by the installation, such instructions are not to be accepted.
The fruit may have to be kept under controlled atmosphere (CA) conditions at low oxygen concentrations.
In general, at the time of the loading the cargo should preferably have a temperature in accordance with the prescribed carrying temperature. However, in certain trades such as the banana trade the fruit is often not pre-cooled.
Prior to loading, pulp or spike temperatures should be taken and recorded. The visible condition of the cargo should be in order. Cargo that does not meet these criteria should be rejected for loading.
In case different varieties of fruit are to be carried in the compartments or even in one hold, care should be taken that ethylene, produced by certain fruit in high quantities, may induce premature ripening of fruit that is sensitive to ethylene.
In particular in the tropics, the cargo brought alongside should be exposed to the ambient conditions for as short as possible. Depending on the situation, it may be necessary to interrupt the loading operations during the hottest hours of the day.
The size of the open part of the hatchways has to be kept as small as practically possible.
The cargo should be stowed properly and in a seaworthy manner. In order to avoid a short circuit of cooling air the cargo should cover the entire floor without open spaces.
The weight of the forklift trucks, in case of palletized cargo, should be in accordance with the prescribed allowable weight exerted on the floorboards.
If the volume of the cargo is less than the volume of the compartment the height of the stow has to be customized as far as possible and/or the floor gratings/boards have to be covered with tarpaulins. This in order to avoid a short circuit of cooling air.
In case that pallets are stowed on a partially loaded deck, the openings of the pallets are to be sealed as to avoid short circuit of cooling air.
Sufficient space has to be left above the stow to allow the air reaching the return air openings. If the height of the pallet loads is such that it covers part of the return air openings it should be considered to stow lower pallets in way.
If there are no return air openings in the corners of the upper part of the hatch coamings, the cargo should be kept away from the inside hatch coaming.
After completion of the loading of each individual compartment, the cooling of the cargo should commence immediately.
It is recommended not to take bunkers during the cargo operations, i.e. with open hatchways and open fresh air openings of the cargo compartments. If sounding pipes of bunker tanks are situated inside the deckhouse, where also the entrance to the cargo compartments is situated, the fumes from open sounding pipes may enter the cargo compartment and cause off odours. Serious claims in this respect have been lodged in the past.
During the voyage
During the voyage, the temperatures and atmosphere in the cargo compartments should be kept in accordance with the prescribed parameters and the values properly taken and recorded.
If possible, pulp temperatures are to be taken of the fruit in way of the fan rooms.
The evaporators should be kept free from ice as much as possible. During defrosting of the evaporators, the situation in the cargo compartments/cooler rooms should be checked to verify that de defrosting water is drained to the bilge and not gathering on the floor of the cargo compartments. This to avoid that this water is blown into the air channels under the floor gratings.
The bilges have to be sounded on a daily basis and free water pumped out as far as necessary.
If cargo is stowed in cargo compartments which need air circulation only, it should be noted that the air circulation fans develop quite some heat and therefore a touch of refrigeration may be required.
If cargo is carried under controlled atmosphere conditions, great caution should be exercised as these compartments are not safe to enter. Before entering the compartments, these should be well ventilated with fresh outside air.
Prior to opening of the weather deck hatch covers, these have to be swept/mopped in case they are wet. The tween deck hatch covers need to be swept, prior to opening, as to avoid that debris and dirt may fall on the cargo in the compartment below.
Pulp or spike temperatures are to be taken and recorded so that documented proof can be produced in case of claims lodged at a later stage.
The hatch covers are only to be opened shortly prior to commencement of the discharge operations and are to be closed during stevedores' breaks.
It should be considered, and sometimes this is mentioned in the carriage instructions, to have the reefer installation in a working condition with the fans at slow speed as stevedores may complain regarding the noise produced by the fans at middle or high speed.
In case the stevedores have to walk on top of the cargo during loading and discharge operations so-called walking boards have to be used to protect the cargo.
At any stage, smoking in the cargo holds is not allowed. The same goes for glass bottles and any other foreign matter that people may bring with them into the holds.
Most reefer vessels are fitted with deck cranes, which may be used for loading and/or discharging. The lights fitted on such cranes should be protected in order to avoid that broken pieces may contaminate the cargo.
In case of leakage from the hydraulic hoses and equipment of the cranes it has to be avoided that hydraulic oil will contaminate the cargo.
Preferably check lists, as part of the vessel's ISM procedures, should be kept, mentioning all relevant details during the various stages of the operations. This as a proof of cargo care during the time that the cargo is in the vessel's custody.
The Association is grateful to Van Ameyde Marine for contributing to the article.