Ten key points for the use of refrigerated trucks and how to use them correctly to avoid risks

Refrigerated trucks are becoming increasingly popular for transporting a wide range of goods, including food, pharmaceuticals, chemicals, electronics, flowers, high-end clothing, and furniture. Their purpose is to ensure the quality and stability of products during transportation. However, incidents of product damage still occur during use, mainly due to incorrect usage of the refrigerated truck. So, how should we use refrigerated trucks? And how can we avoid the risks associated with improper use?

1. Proper operation can ensure that goods are stored and transported in good condition.

Only by using and operating a refrigerated truck correctly can the goods be properly transported and preserved. This is because refrigerated trucks are specifically designed for temperature-sensitive products, and ensuring the correct temperature is key. Improper use or operation can result in goods not being stored or transported in good condition.

2. Performing preventive maintenance can minimize maintenance and operating costs.

Maintenance and upkeep of both the vehicle and the refrigeration unit are essential during normal use. Only by performing regular and correct maintenance can the equipment be used normally and its service life extended. Typically, the chassis engine is maintained based on the driving mileage, while the refrigeration unit is maintained based on the working hours of the engine. The refrigeration unit usually requires maintenance and upkeep every 500-700 hours, which includes replacing the oil filter, fuel filter, and air filter. It is also important to check the tightness of the belts and for any leaks in the refrigeration system.

3. Appropriate packaging is crucial for protecting goods.

For frozen cargo, non-ventilated packaging boxes are used, while for fresh cargo, packaging boxes with ventilated side walls are required. The packaging boxes must be crush-resistant. Since it is not allowed for air to blow over the surface of frozen goods, as it can cause loss of moisture and lead to a decrease in product quality, adequate ventilation is not required for frozen goods. However, fresh goods require good ventilation and air exchange, as they are prone to spoilage due to their inherent characteristics. It is therefore essential to ensure that such goods have adequate ventilation and air exchange.

4. Set the temperature controller to the desired temperature, pre-cool the cargo compartment for 1.5 hours to remove the heat retained in the compartment, and turn off the refrigeration unit when loading the goods.

When loading goods, it is necessary to pre-cool or pre-heat the cargo compartment. This is because the vehicle is usually parked outdoors, and the temperature inside the compartment is the same as the outside environment. If the temperature of the goods being transported is not the same as the environment temperature, loading the goods into the compartment will cause the environment temperature to affect the temperature of the goods being transported, leading to changes in the quality of the goods being transported. Therefore, it is necessary to pre-cool or pre-heat the cargo compartment to the required temperature before loading. However, it is important to turn off the refrigeration unit when loading or unloading goods. Many people make the mistake of leaving the refrigeration unit on during loading and unloading, but this is not recommended.

The reason for this problem is that, after pre-cooling the cargo compartment and without turning off the refrigeration unit, when the cargo compartment door is opened, the fan of the evaporator of the refrigeration unit will be working. The front of the fan has positive pressure while the back has negative pressure. This causes cold air to blow out from the top of the cargo compartment while sucking in hot outside air rapidly from the bottom, resulting in a rapid increase of temperature inside the cargo compartment. However, if we first turn off the refrigeration unit and then load or unload goods, the fan has stopped working and the air flow is completely stopped, so the air pressure inside and outside the cargo compartment is the same. This reduces the speed at which the outside hot air transmits into the cargo compartment.

5. The cargo must be pre-cooled to the required temperature, and the temperature of the cargo must be checked during loading. The refrigeration unit is used to maintain the temperature of the cargo, not to lower it.

Therefore, when loading the goods, the temperature of the goods must be measured first. If the set point temperature of the refrigeration unit is higher or lower than the temperature of the goods, it is difficult for the temperature of the goods in the compartment to reach the temperature required for transportation. The storage temperature of the goods must be consistent with the transportation temperature. If the temperature of the goods changes frequently, moisture will be lost, which will cause changes in the quality of the goods, and as a result, the shelf life of the goods will be shortened.

6. Even if the capacity of the refrigeration unit exceeds the actual needs, insufficient air circulation can still be the main cause of goods deterioration.

A qualified refrigerated truck must ensure that there is good ventilation on all six sides of the compartment and no obstruction on all six sides of the goods; good air circulation can ensure that the goods are transported at the appropriate temperature requirements. The cold (hot) air blown out by the refrigeration unit separates the cold (hot) source entering the compartment from the outside world from the goods, thereby protecting the goods. If a certain position is blocked, the cold (hot) source of that part will directly enter the goods, causing changes in the temperature of the goods. Ensure that the return air baffle is in good condition; do not block the entrance (return air) of the evaporator; insufficient return air will cause irregular circulation of cold air and cause the top goods to freeze.

7. The goods must be stacked on double-sided pallets; fresh goods pallets cannot be wrapped in shrink film, as the film will block the circulation of cold air to the goods; the floor under the goods must not be blocked.

The floor of general refrigerated trucks is usually made of aluminum rails with ventilation; however, some refrigerated trucks use flat anti-skid floors without aluminum rails. Transport companies or companies transporting dairy products usually use flat anti-skid floors, which are suitable for the transportation of multiple products or easy cleaning of the ground. However, when loading goods, it is necessary to use double-sided pallets to ensure the circulation of cold air on the ground. It is strictly prohibited to stack the goods directly on the flat ground.

8. Do not stack the goods in front of the evaporator outlet, as this will obstruct the airflow of the refrigeration system; obstruction above the goods will cause a short circuit of the air flow. Maintain a minimum distance of 225 mm between the top of the goods and the roof of the truck to ensure proper air circulation.

When loading goods, do not stack them too high. It is important to ensure that the loading height is not higher than the level of the air outlet. If the air outlet is blocked by goods, or if the goods are too close to it, it will impact the temperature control of the cargo and may cause the refrigeration unit to malfunction. If the air outlet is blocked, the airflow of the refrigeration system will be obstructed, resulting in a local temperature increase of the cargo. Additionally, some defrosting designs of refrigeration units use air induction defrosting.

When the goods are too close to the air outlet, the coils inside the evaporator of the refrigeration unit will quickly frost, and the air induction switch will then be triggered, causing the refrigeration unit to quickly enter the defrosting state. When the coil temperature rises to design, the defrosting will end immediately. So the refrigeration unit will repeat the above operations, causing the temperature inside the truck body to not decrease. One might feel that the refrigeration unit is defrosting frequently, but it is actually caused by stacking the goods too high (or too many).

9. The inside of the truck body must be kept clean. Packaging paper and debris should not be left on the floor, as they can obstruct airflow or be drawn into the evaporator. Keeping the cargo area clean and free from debris is important for maintaining proper air circulation and preventing contamination of the goods.

Maintaining cleanliness of the floor inside the truck body is important when using refrigerated trucks. Due to the action of the evaporator fan, air circulates inside the cargo area and debris or dirt on the floor can be drawn into the evaporator fan. Over time, a large amount of impurities can be drawn into the evaporator coils, affecting the refrigeration effect of the refrigeration unit. The coils will be gradually surrounded by impurities, leading to a decrease in the heat exchange rate of the coils. Therefore, after a few years of use, the refrigeration effect of the refrigeration unit may not be as good as before, aside from any underlying technical issues, due to the coils being too dirty. Therefore, ensuring the cleanliness of the floor inside the truck body is crucial for the proper operation of the refrigeration unit.

10. Proper handling should be employed when loading and unloading goods. When the truck doors are open, the refrigeration unit should be turned off. The doors should be kept open for as short a time as possible, and strip curtains should be used when loading and unloading goods. It is also important to use partitions to separate non-perishable goods from perishable goods.

To maintain the temperature of the goods inside the cargo area, it is recommended to use strip curtains for urban distribution vehicles. This helps to ensure that when unloading goods quickly (without turning off the refrigeration unit), the cold air inside the cargo area does not quickly escape. Different temperature goods should not be stored in the same space. They should be separated and placed using partitions. Since the refrigeration unit is used to maintain the temperature of goods, and not to cool them down, mixing goods of different temperatures can affect their temperature and impact the quality of the goods. Proper operation and use of refrigerated trucks are key to ensuring the quality of temperature-controlled goods and maintaining the proper functioning of the refrigeration equipment.