IN PRINT — Keep your cool. Spec’ the right reefer.
Posted: October 3, 2017 by John G. Smith
Nothing spoils a day quicker than rotting cargo, but that’s exactly what happens if reefer temperatures stray beyond an acceptable range. Arguments at a receiver’s dock, insurance claims, and soured business relationships are bound to follow.
The challenges can also take root long before temperatures are set or wheels begin to roll.
Look no further than the insulating value of the trailer when first spec’d. Trailers that have a lower UA number, for example, are better able to maintain steady internal temperatures. Factors such as the thickness of insulation along trailer sides, roof, floor, front wall, and doors will make a difference here, as will the application methods meant to ensure a tight seal.
Nothing lasts forever, though. That insulating value will degrade over time, especially when trailer liners or -fasteners are damaged by careless forklift -operators, creating unwanted paths for moisture. A mere cubic foot of water also weighs 62 pounds. In two to three years that can add about 1,000 to 2,000 pounds to a trailer’s weight just because of -regular activities like pressure washing.
“In cold temperatures, the water -molecules will freeze and it will crack the little foam cells,” adds Craig Bennett, senior vice president – sales and marketing at Utility Trailer. “Then it goes down to Florida and it melts, and you’ve got moisture.”
The choice of liners and other protective barriers will make a difference. “Standard liners do not completely seal the insulation and allow an outgassing effect as the trailer ages,” explains Chris Lee, vice president – engineering at Great Dane Trailers. “Eventually the insulation will degrade so much that the -refrigeration unit cannot properly pull down or have enough cooling capacity to get the job done.”
Duty cycles will dictate how important an extra layer of protection will be. While a long-haul operation might open the barn doors twice a week, a food service operation might see the trailer loaded two or three times a day.
When frequent loading and unloading is a fact of life, enhanced wear bands, walls and floors will return dividends. Premium linings might be 40% thicker. “You can double the thickness. Some of the leasing companies do that,” Bennett says. “Some of the grocery chains do that because [forklifts] bang the walls pretty hard.”
It’s not the only way that loading -procedures need to be considered. A fleet that pulls rolls of paper during backhauls might want to choose a floor with a 20,000-pound rating rather than a standard 16,000 pounds, Bennett says. Those who haul loose cargo, meanwhile, will benefit from logistics tracks to tie everything in place, and palletized freight will dictate the need for a flat floor. If cargo sits flat on the bottom of the trailer, a ducted floor can offer a vital channel for return air.
The seals around individual openings are another factor to consider.
“Door gaskets get ripped or cut, or sometimes they freeze to the rear door frame — particularly when you go from a cold environment to a hot, humid environment,” Bennett explains. It’s why Utility uses vinyl instead of rubber.
It isn’t the only way that a manufacturer’s material choices will affect insulating values. Some side posts, roof bows, and floor sills conduct heat more than others, and each cargo track, vent door, side door, or additional crossmember needs to be considered, Lee says. Bennett also observes that pre-coated white aluminum skins are popular for a reason. They reflect the sun better than stainless steel.
The trailer’s insulating power will ultimately dictate the choice of reefer unit needed to cool the air, too. “You can sacrifice half an inch of foam in the walls for a 30,000 BTU reefer unit,” Bennett says as an example. Otherwise, a 25,000 BTU reefer might do.
Aside from the required power, many systems are differentiated by the insights and controls delivered through telematics.
Patrick McDonald, product manager – trailer products with Carrier Transicold, refers to verified temperatures and setpoints, alarms for out-of-range temperatures, and geofenced locations as a few examples of data that can be generated.
“Fleets may further want to enable the ability to track fuel consumption,” he adds. A sudden loss in fuel economy could be the sign of damage, but also theft. When a thief opens the door to steal cargo, after all, the reefer will begin to work harder as it attempts to maintain temperatures.
“We’re able to tell the customer if they’re in the right mode and if the mode doesn’t match the Bill of Lading,” says Gayatri Abbott, product manager – connected solutions at Thermo King. It’s even possible to change settings over the air, either with a fleet computer or through a mobile app given to the driver. Alarms and reefer states can also be integrated into dispatch and planning systems.
Information about everything from an open door to actual temperatures can even be automatically sent to shippers when a load is delivered. “You can prove that the reefer never failed,” she adds, noting how shutdown alarms can be tracked. “All reefer parameters, plus door, fuel location, all of those come together to give you that traceability.”
As valuable as telematics can be, -however, it presents a power-related challenge. Batteries might struggle to keep up with layer upon layer of devices and sensors. But the lives of these electric power sources can be extended by introducing solar panels.
“Each [device] draws power — sometimes up to a few amps per hour — while the refrigeration unit is off,” McDonald says. “The benefit of using solar panels to maintain battery charge is ensuring that there is ample power for system starts.”
“It has a significant effect on alternator life because it doesn’t have to go to 100% output,” says Thermo King’s Paul Kroes, power management business development manager.
While the panels are clearly valuable tools, there are also considerations to ensure they are protected.
“You want to be as low as possible, especially when you’re looking at snow scrapers,” Kroes says, referring to the panel profiles. Abrasion resistance will help to fight against the scrapes caused by overhead tree branches. “You want something that will follow the curvature of the roof,” he adds. And chemical resistance is important in the fight against aluminum brighteners used in pressure washes.
Solar power aside, there are other environmental footprints to consider.
“Refrigerant is also an important consideration,” says McDonald, noting that today’s Carrier Transicold units use less refrigerant than earlier models. And later this year, the company will begin offering optional R-452A refrigerant, which has about half the Global Warming Potential (GWP) of R404A.
Environment Canada is considering a ban on refrigerants with a GWP higher than 2,200, to be applied to transportation applications after 2025. At a GWP 2,140, the R-452A would be allowed.
Clearly there are plenty of issues to consider when you want to keep your cool.