Rick Mullininx, vice-president of engineering for Great Dane Trailers, says one of the best ways to understand the intricacies of trailer design is to picture a rubber balloon filled with helium and how, over time, the rubber degrades, letting the helium escape.
“One of the biggest challenges to making a refrigerated trailer last longer [is that] the insulation that holds the cold air inside starts to break down,” says Mullininx.
“Once that starts to happen, the cooling unit itself must [work even harder] to maintain the desired temperature. It burns more fuel and requires more maintenance over time, adding to the operating costs of the refrigerated trailer,” he notes.
So reducing the overall life cycle cost of a reefer isn't just a matter of extending the life of basic components such as doors, landing gear, axles and tires, etc., but also extending the life of the trailer's insulating properties.
Insulation degradation is one of the things that makes reefers so much more complex than dry van trailers, Mullininx points out.
That's where ThermoGuard comes in. Mullininx and his engineering team spent three years developing this glass-reinforced, thermoplastic liner. Their purpose was twofold: to improve the insulating capability of the trailer, as and to ensure that the insulation weighs less and lasts longer.
Compare that helium-filled rubber balloon to one made of tin foil. Since foil is stronger than rubber it will keep more of the helium in the balloon over longer time span — or in our case, the cold air inside the trailer.”
“As a refrigerated trailer ages, the effectiveness of its insulation system continually decreases because traditional liners do not completely seal the insulation and allow ‘out gassing’ effects that cause the foam insulation to degrade over time,” Mullininx says.
“To combat this, ThermoGuard contains a composite layer that seals the trailer's insulation and significantly reduces this traditional loss in insulation performance.”
The material also adds strength, durability and extreme puncture resistance to the liner, as well as saving weight — up to 200 pounds, depending on the type of reefer — which further helps to improve the life cycle cost and usable lifespan of the trailer, according to Mullininx.
“The value of a refrigerated trailer is contingent on its thermal performance. It is imperative that a reefer operates efficiently not only today, but also for the life of the trailer,” he notes.
“Using a glass-reinforced thermoplastic liner dramatically reduces foam aging, and consequently creates a longer lifecycle and should help improve resale value as well.”
Complicating the process even further is the need to use a liner material that is easy to repair. There's no way around the fact that trailers are exposed to difficult work environments, which means liner damage is inevitable. So it's especially important to minimize excessive downtime and expensive repair processes.
“We used to use liners made from Thermoset, a polyester resin,” Mullininx explains. “Repair kits came with the resin and a catalyst that maintenance personnel could mix by hand and then apply to the damaged area — a messy process that took a lot of time.
“With the thermoplastics in the ThermoGuard liner, however, you basically use a hot glue gun to repair it — a much simpler and faster process,” he points out.
The liner is only one piece of the reefer's life cycle puzzle, however, so Mullininx and his engineering team continue to look at ways to improve the corrosion resistance of the trailer body and use more long-life electrical harnesses.
“We constantly think about what it costs to run a refrigerated trailer and ways we can make it last longer without costing more to operate,” he explains. “It's not harder to achieve longer lifespan and lower life cycle costs for reefers as compared to dry vans. There are just more things we need to keep track of and improve over time.”