Refrigerated Transport
There are many types of refrigerated trucks employing many types of devices and technologies to ensure the transportation of perishable foods at the required low temperatures. But failure by transport operators and drivers to execute proper care of product as well as vehicle can easily break the cold chain.
Refrigerated trucks can carry goods at extremely low temperatures, but it must be understood that refrigerated trucks and insulated or ventilated trucks are not the same. In the latter, there are no cooling devices fitted for providing extremely low temperatures. Insulated or ventilated vehicles carry, for example, perishable foods such as fruit and vegetables, while refrigerated vehicles carry frozen meat.
Refrigerated vehicles can be ice-cooled or fitted with various types of mechanical refrigeration systems. Other trucks use carbon dioxide gas or certain types of liquids as cooling agents. When the consignment being transported is big or the distance to be covered by the refrigerated truck is large, articulated trucks are mostly used. These trucks carry refrigerated vans or semi trailers.
When buying a new refrigerated truck or trailer, certain features should be noted. Starting with the construction of the refrigerated area, it is imperative that rigid polyurethane foam is used to protect the goods from tugs caused by the many bumps and, of late, potholes on our roads, which can cause damage to transported goods.
The use of polyurethane is gaining significance in the production of refrigerated trucks. Polyurethane has high mechanical strength but low weight and it provides high insulating capacity but the wall thickness is quite low.
Insulated truck bodies must be manufactured from extremely hygienic materials, i.e. metal cladding or fibre-enforced polyester panels which are odour-free and easy to clean.
Wall panels can be clad with various finishes to suit a client’s particular needs: galvanised steel, Chromadek or stainless steel.
Doors must be robust and air tight, and made from the same insulation and cladding as the wall panels. Floors can be made from standard panels reinforced on the upper surface with plywood and covered with stainless steel, galvanised steel or lined with fibreglass.
At times, temperatures as low as -35ºC have to be maintained and thus it is very important that water must be prevented from diffusing through various channels.
The minimum thickness of insulation that must be adhered to are as follows:
Sidewalls: 55 to 65 mm
Roof Panels: 70 to 100 mm
Floors: 100 to 115 mm
Bulkhead: 70 to 100 mm
Doors: 70 to 100 mm
A refrigerated truck system must have sufficient capacity to remove heat generated by outside plus inside elements such as heat emitted from produce during the ripening process. Body and door seals should always be kept in a perfect condition to prevent heat from outside entering through small holes or cracks, and the floor must be able to avert heat from the road.
The mechanical refrigeration unit must have (diesel compressor driven diesel powered units):
• a fan capable of circulating at least 0.944 m/s of air against a 50 mm water gauge static pressure;
• a large evaporator coil to maintain constant temperature;
• a solid state temperature controller (thermistor);
• a thermostat that has a change-over switch for delivery and return air control;
• a thermograph or temperature recorder to supply continuous temperature history;
• thermo-couples in the delivery and return air streams for temperature checking and calibration of the thermostat;
• rigid ducting to facilitate even distribution of cooled air throughout the trailer.
The condition of a trailer is as important for maintaining the temperature of products as is its design.
Vehicle owners or operators must pay attention to the following aspects:
• Dirty trailers may contaminate produce due to certain odour build-up within the vehicle. Dust, dirt and small waste left behind from previous shipments should be swept out of the refrigerated area before it is washed. Dirty bodywork absorbs more heat as it is not able to deflect it.
• Damaged wall and floor insulation allows excessive heat to be conducted from outside into the trailer, and faulty doors and cracked door seals won’t be able to maintain proper temperature control and will allow dust to enter the trailer. Cracks in the wall and floor may harbour dirt and pathogenic micro-organisms.
• Sealed steel plates that are not properly fitted may damage loads or allow for fungal growth or insect breeding behind the plates.
• Blocked and dirty cooling coil plenums and return air ducts will not be optimally efficient during cooling.
It is of utmost importance to keep food products at the correct temperature from the time of loading throughout traveling and offloading in order to avoid deterioration of the products. Proper loading and offloading procedures and temperatures must be documented by the driver and signed off by the cold store operator.
Before transportation takes place the product as well as the vehicle must be pre-cooled to the same specified temperature for both, meaning that the product should always be loaded at the correct temperature when removed from the cold store. Fast loading (within 30 minutes) is also vital, and should ideally take place from an enclosed pre-cooled loading bay.
The driver, who should be sufficiently trained in transportation of refrigerated products and supervise the loading procedure to ensure that no cargo or vehicle is damaged in the process, must ensure the following:
• Vehicles arrive in a clean state at the loading point.
• Prior to loading, the trailer and products are pre-cooled, the trailer is set at the correct temperature setting and the cooling unit is functioning correctly.
• The cargo is loaded in such a way as to maximise air flow within the trailer.
• Damaged packaging and products are removed.
• Cargo in partly loaded vehicles is properly secured.
• Temperature checks are performed and documented.
• The refrigeration unit is functioning correctly whilst refrigerated cargo is being transported.
The same supervision must be followed during the offloading process, during which the driver should perform the following functions:
• Keep the refrigeration unit running until the doors are about to be opened, and switch it off as soon as the doors are opened.
• Record the hour meter reading when the refrigeration unit is switched off and indicate the time of reading.
• Should the consignment not be accepted, ensure that the reason for not accepting the consignment is stated on the delivery note.
• Report all problem arrivals, for example warm temperatures, damaged cargo or any quandary in terms of the vehicle to the owner.
One of the main problems keeping the freeze temperature constant inside refrigerated trucks is the constantly varying outside temperatures. To monitor the situation the use of RFID (Radio Frequency Identification) is a valuable tool.
RFID is basically a wireless system utilising sensors, called tags or transponders, which can accurately detect temperature changes by half a degree Celsius and transmit the information in real-time to system users. These tags are able to store, retrieve and use data wirelessly.
RFID assists managers in keeping their eye on the temperatures inside refrigerated trucks and trailers whether they are on the move or stationary. Whether a truck is being loaded or offloaded, the low temperature still needs to be kept constant in order to prevent the goods from deteriorating.
SERCO Industries specializes in the design and manufacturing of insulated and dry freight truck bodies and trailers.
These trailers are relied upon by Southern Africa’s leading transporters and long-distance haulers to carry everything from ice-cream to day-old chicks, from beef to bread – safely and hygienically.
SERCO’s success as a market leader can be attributed to our design, innovation, and the quality of our products and services.
With extensive experience in our specialized field as well as our in-house design capabilities, you will have no doubt that you have selected the right partner to “give you the edge” in a competitive market.
Serco has grown exponentially into one of South Africa’s leading and most trusted insulated and dry freight truck body and trailer building companies.
Ice Cold Bodies (Pty) Ltd, situated in Heidelberg, Gauteng, is also one of the best and most respectable body and trailer manufactures in the industry.
Ice Cold Bodies specialize in high quality insulated truck bodies and trailers for the transportation of frozen, chilled and dry freight products as well as livestock.
They also specialize in various steel trailers such as flat deck, drop sides, curtain sides, skeletal, walking floor and low bed trailers.
