Having a trailer in good condition is as important as ambient (outside) temperatures in affecting the condition of a load of perishable produce.
With age, trailer insulation deteriorates, notes Rich Macleod of TransFresh Corp. of Salinas, CA. However, a bigger threat to trailers are the beatings they take from forklifts and pallets “that tend to attack those sidewalls. They tend to stretch them, buckle rivets, punch holes. All of that gradually degrades insulation. Then moisture gets into that insulation,” Macleod states.
Drivers should check the manufacturer’s stated value of insulation over time that collects moisture. It is the damage not only to interior walls, but outside trailer walls that excellerates the degrading process, he notes. These same principals apply to summertime hauling as well as loads in wintertime.
“If you have damage to the outside of the trailer and are driving though a rain storm, moisture is getting in the insulation. Then you get in some 25-degree (F.) weather and the insulation with moisture is freezing. Then there is no insulation value,” Macleod says. ” You are just creating an ice block. Now you are hauling around an ice block instead of insulation.”
The condition of trailer doors also is important. Make sure the door is sealing properly.
Macleod says the rules for temperature control in the trailer are the same for summer and winter, except when it gets down to 25 degrees F. or less. Then there is more leeway in moving the set point on the reefer unit upwards to protect the load.
Additionally, Macleod notes if hauling tropical fruit that is subject to cold temperature injury, be especially careful with the loading pattern, as well as make sure the reefer unit is performing as it should.
Manufacturers of trailer refrigeration units have made significant progress in controlling air temperature, air return and air output sensors because of improved and better written computer programs, he notes.
Macleod says this results in loads of fresh product being less likely to freeze, or to become too warm. It used to be the air going into the trailer unit was above the set point, it would put out an unlimited amount of cold air. In some cases the cold air going through the air chute would freeze product in the back of the trailer. This gets the BTUs in the trailer without having to drop the temperature.
“They have been able to write the programs into the reefer unit that controls the air out put much more effectively so you don’t get the temperature extremes such as freezing and warming in the load, because you are able to control that air flow much better,” Macleod says.
Now manufacturers have designed equipment to control the air to go only a certain amount of degrees from the set point. Additionally, the fan will go into high speed for air circulation, rather than at a lower speed, to encourage air mixing.
(Rich Macleod is vice president, pallet division North America for TransFresh Corp., Salinas, CA. TranFresh provides Tectrol, a service where the atmosphere integrity of berry shipments is maintained at a 10 percent or higher CO2 level. This provides better quality arrivals of berries and longer shelf life.)