- Pre-cooling of Cargo
Products should always be pre-cooled to the required carriage temperature before being packed into the container.
This will maintain the quality and freshness of perishable products and avoid spoilage.
Reefer containers are designed to maintain the temperature of the products they contain, not to lower it.
Cargo stuffed at temperatures above carriage temperature can cause considerable strain on the reefer unit and may eventually result in a breakdown.
Cargo must be properly pre-cooled to its desired temperature prior to packing unless loading in a Cold Tunnel concept.
Ensure reefer container has been set with the correct temperature setting.
Air vents are to be opened to the required setting to release carbon dioxide and ethylene gas based on its desired respiration rate. (For chilled cargos that are perishable and limited holding shelf life.)
Switch off the reefer machinery during cargo stuffing to avoid condensation.
It is important to note that reefer containers are designed to maintain the temperature of the products and not pre-cooling it. Pre-cooling is a separate operation performed prior to storage or transportation that requires special equipment or cooling facilities.
Pre-cooling of the reefer container itself should not take place unless temperatures in the cold store and in the container are identical and a "Cold Tunnel" is used.
A Cold Tunnel is a tight duct between the cold store and the container, which prevents ambient air from entering. If the container is pre-cooled in an open environment, ambient hot air will meet internal cold air once the doors are opened resulting in condensation on the interior surfaces. Condensed water can drip from the roof of the container and cause stains and frost on the boxes.
If loading in a Cold Tunnel concept, the machinery may operate during loading.
Do not operate reefer machinery when container doors are open. Hot ambient air will rapidly move into the container and heat up the cargo instead. When humid air enters the reefer, moisture condenses on interior surfaces and product, which may cause quality of outturn at destination.
If inland transit time is greater than 2 hours for chilled cargo and 8 hours for frozen cargo, it is recommended to use the generator set to supply power to container during inland tracking.
If a generator is not available, it is recommended to keep the container power on for 6 hours prior to the transport. This will allow the machinery to expel the ambient air that has accumulated inside the container during loading. Thus, the product temperature is stabilized before transport.
Latent heat from external ambient air may cause a rise in carriage temperature if the reefer unit is left off power for too long.
Hence, it is always recommended to truck reefer cargo in as cool a climate as possible (i.e. at night), or with clip on generator set to ensure continued power supply during land transportation.
- Stuffing of Cargo
Stuff the container within shortest time possible so that the ambient temperature does not affect the container and the cargo.
Ensure packages are stowed with adequate spacing in between for "good" airflow.
Air pockets should be minimised.
Similarly, cargo should not be packed too near to the door end as it will cause short cycle of airflow.
Cargo should be stowed with the floor grill at the door to ensure proper ventilation. Failure to do so could affect perishables, resulting in poor outturn.
Cargo should never be stored above the red load line within the reefer container; otherwise it will impede the airflow, which could affect the quality of product outturn.
Cargo weight must be evenly distributed throughout the container floor space. The top part of packed cartons should be parallel.
Do not leave large spaces where cargo could collapse during transit.
The total cargo weight should not exceed the maximum payload within the container.
The total gross weight (including container tare weight) should not exceed the road limitation in any transit points during the transportation journey.
Upon completion of stuffing, seal the laden refrigerated container with PIL Bolt Seal (bullet seal).
Cartons must be designed to withstand the weight of other stacked cartons. Overloading cartons and stacking them beyond their design limits can cause damage to the cartons and their contents.
If needed, use a wedge or chocks to secure material in the container.
The products should be stacked as a solid block, without any space between the cargo and the walls of the container.
If the cargo cannot cover the entire floor area, filler such as dunnage or cardboard must be placed over the empty space to assist with the correct airflow. Air will always take the route of least resistance, thus a "short circuit" of airflow may result in insufficient cooling of the cargo
Serves to increase cargo-handling efficiency
Two major types of pallets, "Europallet" and standard pallets. Size of the "Europallets" is 800mm x 1,200mm per piece while the size of standard pallets IS 1,000mm x 1,200mm per piece. A 20' container can hold eleven "Europallets" in one tier or nine to ten standard pallets in one tier while a 40' container can hold 23-24 "Europallets" in one tier or 20-21 standard pallets in one tier.
Wooden pallets must be strong enough to allow storage of three tiers when loaded.
Carton boxes must not overhang the edges of the pallets. On the other hand, boxes, which utilize less than 90% of the pallet surface and do not align with the pallet edge, can shift in transit.
It is strongly recommended not to mix load different types of commodity under same load. Some of these cargos (mainly chilled fruits) have its own required temperature and carrying condition (air exchange). E.g. Produce with high ethylene content can cause rapid deterioration to highly sensitive cargo like grapes, plums, nectarine, etc.
- Packaging to use
What type of packaging to use before transportation and loading?
Correct packaging allows produce to ventilate, transpire and emit ethylene and CO2.
Produce should be packed closely or tightly secure to prevent bruising and crushing during transportation. Plastic and bubble wraps can be used to enhance protection.
Peaches were bruised due to improper packing
Packaging should be strong enough to protect and carry the produce. It should also allow ease of loading, unloading and sales.
- Improper Cold Chain Management
Although trucks are covered with tarpaulin, it offers little protection from sunlight and ambient air.
Produce exposed to sunlight will transpire and physiological growth rapidly takes place.
Non-palletized cargo. Shows long unloading process to pack lychees into cold room.
Workers unload potatoes onto pallets. This is a lengthy process and as a result may shorten the shelf life of the produce.
- Measures to be taken during delivery
When products are delivered to the cold room:
Doors should be closed at all times to prevent exchange of cold and hot air.
If doors cannot be shut, there should be rubber sheets at entrance to prevent cold air escaping out of the cold room.
Produce are left along the corridor of a cold room. Temperature may not be ideal for produce which is subjected to condensation.
It is not advisable to leave the produce at the corridor of a cold room as produce may be subjected to condensation where the temperature is not ideal.
Wet floor due to condensation
- Inspection and Trimming
When cold chain procedures are not in place, a lot of cargo does not arrive at its destination with the desired quality.
Produce has to be trimmed as stems or outer layers of produce are exposed to bacteria.
As time passes by, the condition of produce could deteriorate further when subjected to inconsistent and distressing temperature.
Process of Trimming
Produce is left exposed to ambient temperature waiting to be trimmed.
Outer layer of lettuce turns yellowish and is trimmed away.
- Cold Chain Practices
Shipper should maintain the product at the desired temperature to keep it fresh, minimise release of CO2, ethylene and respiration.
Trucks able to deliver within shortest possible time
Temperature is set correctly and condensation should be minimized.
Packing Facilities/ Pack House
Ensure produce is palletised and adequately stabilised in the cool room.
Ensure reefer container is ready for loading before removing produce from cool room. Container has to pass pre-trip inspection.
Land Transport to Terminal
Vehicle should have effective insulation and cooling system. Transportation time should be minimised. Trailers must have proper twist lock fittings and must travel directly from shipper place to terminal.
Ensure temperature is set and ventilation is in accordance to shipper’s instructions. Container has to pass post-treatment inspection.
On Board Vessel
Reefers are to be plugged on immediately after loading. Regular monitoring of vessels at 4-6 hours intervals. Look out for necessary repairs. Terminal technicians are to record all call-outs and temperature readings.
Direct destination/ Transshipment Port
Reefer containers are to be plugged off only when loading process is ready to be conducted. Reefer containers must be powered on immediately upon delivery to reefer yard.
Cargo must be monitored while waiting for on-carriage.
On Carriage Vessel Operator
Reefer shipment will always be given priority to load on first available carriage, as cargos are usually perishables and with limited holding shelf life.
Discharge Port Terminal
Reefer temperature must be monitored regularly before consignee collects cargo.
Land Transport to Consignee
Minimise trucking time to consignee location.
When cargo is ready for un-stuffing, the unloading process must be conducted at shortest possible time to minimise heat exposure to the produce. Cargo must be unstuffed and loaded into cold room immediately. If un-stuffing only takes place at later stage, the laden reefer container must be plugged-in to ensure power supply is on to maintain the temperature.
To ensure good cold chain process, it is strongly recommended to use cold trucks for transporting the fruits to the supermarkets and retailer stores. Cargo should not be under direct heat as such would cause deterioration rate to increase rapidly.
Many buyers change their supply source due to inconsistent resulting outturn of produce.
*From numerous trials, 85-90% of problems are land-based.
- Airflow Circulation
Reefer units with airflow circulation allow proper cargo loading and airflow.
Excessive space between loads will result in obstructed airflow that does not extend to the full length of the container.
Load placed in the rear of the container will result in short cycling.
Load placed in the front of the container will result in impeded air circulation through the interior of the load.
Different Boxes for Different Products
All chilled products should not be left unrefrigerated for more than an hour. Otherwise, cargo temperature may rise due to respiration during land transit.
- Equipment Checklist
Standard Checks for Reefer Equipment
A PTI (Pre-Trip Inspection) is conducted when containers are released and returned. This is to ensure that containers are available in clean condition.
The PTI process is strongly recommended under frozen mode and within a 6-hour interval.
The temperature of the container has to be pre-set and electronic checks are completed in accordance to PTI procedures issued by PIL Singapore [including updating of date and time (GMT) data].
Upon completion of the pre-trip, the unit must be set for the "start of trip". This would then accurately record the functioning of the machinery from the time of the pre-trip through packing, transport and the voyage of the container.
A pre-trip decal is then affixed to the machinery casing. The decal must show the date of pre-trip date and marked to indicate who was responsible for the pre-trip. Always remove the old decal when a new PTI is conducted.
All new release containers (for export) should have a valid PTI decal; our current policy on validity is 30 days. Thereafter, a second PTI is required prior container release.
The second PTI is to ensure containers are free of odor, smell, damage, leakage and deterioration of corners – PIL food grade cargo.
EIR (Equipment Interchange Receipt) is to be submitted at Port of Load (POL), Port of discharge (POD) and transshipment (T/S) port.
- Parts and Functions
The cold air is supplied from the bottom of the container through the specially designed T-bar floor and sidewalls and this is also known as bottom-air delivery.
Located at back of reefer to provide air flow circulation
Cause of damage if buffer plate is missing: airflow short cycle, froze damage, heat exposure to area where air flow are weaken
Power Sockets (plugs)
All PIL reefers use Cee-Form plugs. Do not tamper with these reefer plugs as they may cause electrocution.
Pins are often cut, especially if used with incompatible female plugs
Probes (Upon Request)
Digital recording of product temperature.
Product temperature can be measured when probe is fully inserted into product whilst ambient temperature can be measured when probe is placed near product.
3 methods of placing the probes:
Into vent hole carton box
Taped to the outside the carton box
The ventilation of fresh, chilled products is necessary in order to remove the respiration gas, carbon dioxide and ethylene produced by the cargo. Heat is removed by continuously circulating the internal air, whereas introducing fresh air into the fresh air circulation minimizes carbon dioxide and other gases.
Closed air vents during land transit
For any land transfer that requires the refrigerated container to be off power, customers should close the air vents for refrigerated containers carrying fruits/vegetables.
This is to avoid any pollutants/contamination (eg: diesel fumes) that may enter the container via the air vents during the land transport
However, air vents must be re-opened to the required setting when the reefer machinery is being switched on subsequently upon arrival at Container Yard terminal. Hence all stations/respective parties are required to check the vent settings are in accordance to shipper's requirements.