Temperature control in reefer containers with thermal covers for unplugged locations
Reefer containers or refrigerated containers are special developed sea containers which are used to transport time-temperature sensitive products over sea, road and rail. To make this kind of conditioned transport possible, the reefers are especially constructed with insulated panels and cooler engines for cooling or heating conditions (standard -25°C to +30°C). This way they are able to create and maintain a certain pre-set temperature environment according to the quality requirements of the loaded products. Reefers offer an ideal temperature controlled transport system for over-sea supply chains, yet there is a consideration to be made.
Although reefer containers offer a stable and automated temperature condition, they are not completely perfect in their temperature management. This due to the interruption of power in the cold chain. When cooler engines (electrical or diesel powered) are electrically powered, the reefer must be connected to a power unit on the vessel in order to function. As soon as the reefer container is “unplugged”, meaning that there is no power connection, the cooler engine is not functioning and the temperature of the outer environment will start to penetrate in the container contaminating the temperature and quality of the loaded products.
Unplugged situations, where the power is not available, can be noticed at overload locations where the reefer container is transferred from the truck to the harbor to the sea vessel and vice versa. These are typical locations where reefer containers in general experience temperature problems. The combination of exposure time and temperature of the environment at the “unplugged” location will determine the impact of the temperature contamination and risks to the products as shown in the following drawings.
Thermal covers for temperature protection at unplugged locations
When reefer containers are used for very temperature sensitive products such as pharmaceuticals with temperature range (+2°C to +8°C) where the temperature is very limited in acceptable heating or cooling without quality impact, the unplugged location can be disastrous for the temperature of these products. Multiple case studies and tests have shown that temperature loggers register too hot or too cold temperatures at these unplugged locations triggering various alarms on quality issues.
In order to offer a solution for these unwanted temperature conditions, thermal covers can be used to protect the pallets inside the reefer. The goal of the thermal cover is to offer temperature protection during the unplugged location reducing or even avoiding any temperature risks or excursions during the unplugged condition. The praxis has shown a very successful usage of thermal covers in reefer transports in which the thermal capacity of the cover determines the time-temperature conditions of the unplugged condition. The higher the thermal quality of the cover, the longer the time or the higher the temperature of the outer environment can be before any product quality damages occur.
The pictures below show the protocol – user manual for implementing TEMAX thermal covers in reefer containers.
When thermal covers or thermal blankets are used to insulate pallets in reefers, it is very important that the thermal cover does not block the airflow of the reefer underneath the pallet. Always make sure that the airflow of the reefer (cooler engine) can flow unblocked underneath the pallet.