Far from just rolling refrigerators, today’s reefer trailers and units pack state-of-the-art technology to protect all types of perishable loads.
Like their dry van counterparts, refrigerated trailers have evolved, and benefited from advancements like computer-aided design (CAD), resulting in lighter, more durable products. “CAD software has enabled us to build a stronger trailer with less material and lower weight,” says Chris Hammond, vice president of dealer sales for Great Dane.
Designing refigerated trailers is especially challenging because controlling temperature requires additional material, but because foodstuffs often are densely packed, weight is a major concern.
“The trick is to make a refrigerated trailer as light as possible – without compromising thermal efficiency or durability,” says Joe Stianche, fleet manager for Sanderson Farms, based in Laurel, Miss.
Special challenges
In addition to standing up to the rigors endured by any other type of trailer, reefer trailers face unique conditions. For example, they must insulate their loads, and resist internal corrosion from load moisture. That’s tricky, since moisture can collect behind seams, scuff liners and fasteners. “We used to use aluminum scuff liners,” says Rod Ehrlich, chief technology officer for Wabash National. “They would dent easily and pull away from the inside walls, and they were difficult to repair. Now, we use a high-performance plastic that’s fused in place. And if they get damaged, they’re easily repaired.”
Ehrlich also cautions against using pressure washers on seams and fasteners, since that drives moisture into the insulation, where it compromises insulating ability and corrodes metal.
Interior materials have improved, says Charles Cole, manager of technical sales and product training for Utility Trailer Manufacturing Co., which claims the top share in refrigerated trailer sales.
“Lining materials are better,” he says, “such as woven glass fabric, like Armortuf by Kemlite.”
“Interior linings have added puncture resistance and reduced weight,” agrees Great Dane’s Hammond, “while adding useful life and reducing maintenance.”
Another consideration is how much solar heat the roof absorbs; the lighter in color the roof is, the better it reflects light and heat, which reduces the load on the reefer unit. But aluminum roofs darken over time, says Ehrlich. “That’s why we offer our Solar Guard roof, which won’t darken. And because it forms a superior bond, we’re able to use half as many roof bows as conventional designs.”
Interior lighting poses yet another challenge unique to refrigerated trailers. That’s because with conventional, fluorescent lights, the colder the interior temperature, the dimmer the lights. Interior LED lighting has become popular despite the cost, explains Great Dane’s Hammond. “LEDs are better suited for multitemp operations because they burn brighter, especially in the front compartment, which is the coldest. In addition, they require less maintenance because they are not as susceptible to shock, and they activate instantly instead of warming up to full brightness.”
If reefer trailers have an Achilles’ heel, it has to be the floor, says Sanderson Farms’ Stianche. “They can only take a finite number of forklift landings before they break,” he says. “And when that happens, the trailer’s useful life is over. They’re better than they used to be, but they’re not quite there yet.”
The big chill
Refrigeration unit manufacturers also are using the latest technologies to reduce fleet costs and improve uptime. For example, Carrier Transicold’s new Vector 1800MT uses the company’s Deltek hybrid system, which received the Truck Writers of North America’s Technology Achievement Award for 2006.
Deltek does away with most serviceable mechanical parts, such as belts and clutches, and it reduces refrigerant charge and fuel consumption compared to conventional systems, says Ignacio Aguerrevere, director of product development and marketing. With this system, an aircraft-quality generator is driven by a diesel engine and provides electrical power, creating a hybrid powertrain. And the electric compressor motor is inside the compressor housing, so no shaft seal is required.
For heating and defrost, electric resistance strips inside the evaporators provide constant heat capacity regardless of outdoor temperature. A benefit of electric heating is increased compressor life, since the compressor is used only during cooling.
The system also has electric standby capability for emissions and noise abatement as well as fuel savings, and an “Advance” microprocessor control system featuring IntelliSet commodity programming and an integrated DataLink recorder.
Finally, says Aguerrevere, diagnostics have been simplified greatly. “It’s a plain language interface, instead of blink codes,” he says. “It will pinpoint the problem component, which will improve diagnostic time.”
Meanwhile, Thermo King’s SB-210 and SB-310 trailer units feature the new Smart Reefer 2 (SR-2) controller as standard equipment, and – according to Doug Lenz, product manager for trailer and rail – design techniques such as FMEA (Failure Mode and Effect Analysis) were used to evaluate potential improvement areas, from temperature control sensors to wiring, software and operator interface.
A FreshSet software feature reportedly reduces product shrinkage, prevents top freezing and extends the shelf life of fresh produce and other temperature-sensitive products. The keypad can be locked to prevent tampering, and a mode lock prevents accidental selection of the wrong set point or mode of operation. It also can diagnose and self-adjust for potential problems before the load is affected. In addition, adds Lenz, “The SR-2 speaks our customers’ language. Drivers instantly understand the status and setup of their valuable cargo.”
Additional features available in the SR-2 include integrated service and cargo loggers, audible set-point notification, diesel/standby-electric auto switching and programmable hour meters.
The SR-2 also offers ServiceWatch, a built-in data recorder, as standard. From the time cargo is loaded until its final destination, the SR-2 can log the history of the trip, and it has programmable maintenance intervals. As an option, the SR-2 features the CargoWatch system, which provides temperature and system data. The SB-210 and SB-310 units come with new factory options for R:COM, i-Box and Trac-King – providing customers with cost-effective data capture, management and communication systems, Thermo King says.
Natural selection
There seems to be little doubt that reefer units and trailers have evolved for the better. “There are better interior materials that reduce wall damage,” notes Sanderson Farms’ Stianche. “And the units are more durable. Refrigerant is no longer a consumable item, electrical systems and controls are more sophisticated and more robust, and self-test capability has really helped.
“I can’t think of an area that hasn’t gotten better.”
