Pick one — precise temperature control, increased route productivity, one-stop delivery, lower risk of driver injury, or reduced delivery stop time. All these reasons have been cited as the basis for attempting multi-temperature delivery, which is so common in the foodservice and grocery industries that many distributors consider it standard operating procedure.
In the past 15 years, the purchase of equipment designed for multi-temp operation has increased among foodservice distributors, but has decreased slightly among wholesale grocers and supermarket chains. For instance, as recently as 1996, 46% of wholesale grocers reported purchasing multi-temp trailers. By 2003, only 29% of wholesale grocers and supermarket chains were buying multi-temp equipment. Multi-temp trailers presently account for only about 12% of the national grocery delivery fleet. These statistics do not include purchases for dedicated carriers from Wal-Mart food distribution centers. All refrigerated equipment contracted to Wal-Mart is equipped for multi-temp operation with three temperature zones.
In contrast to wholesalers and supermarket chains, foodservice distributors rely on multi-temperature equipment (in some form) almost exclusively. In addition to high-tech multi-temp systems with multiple bulkheads and remote refrigeration evaporators to provide positive temperature control for multiple product categories, some foodservice distributors rely on insulated boxes cooled by dry ice, simple portable bulkheads separating cargo space into refrigerated and non-refrigerated compartments, or low-tech systems that attempt to siphon refrigerated air from the coldest cargo compartment into a compartment intended to be held at a higher temperature. Equipment vendors will accommodate both methods, but have placed most of their product development effort behind individually refrigerated compartments.
Early experiments
Some of the earliest experiments with positive temperature control in a second compartment started with refrigeration unit dealers attempting to provide special designs for particular customers. Most notably, some of these dealers used the evaporator and fan section from small truck engine-driven units as a remote refrigeration unit in the second compartment. At least one of these experiments had a remote evaporator mounted on a sidewall track with flexible refrigeration tubing so that it could be moved back and forth in the cargo compartment.
Although these early efforts were built at the dealer level, customers still demanded reliability, so it didn't take long for the major refrigeration unit manufacturers to develop remote evaporators with standardized plumbing and controls, all covered by factory warranty. Initially somewhat bulky, the remote evaporators were built in configurations suitable for mounting on the sidewall of a truck body or trailer or on the ceiling. In either location, they presented a challenge for loading crews because they projected into the load space in an inconvenient way.
With the availability of remote evaporators, the bulkheads separating cargo temperature zones began to develop rapidly. Some fleets preferred track-mounted bulkheads that could be moved fore and aft in the load space and stowed against the ceiling to clear the entire vehicle for backhaul purposes. Although the basic design is still in use, these bulkhead systems have evolved away from heavy units with aluminum skins to much lighter ones with composite or fabric coverings that can be handled with much lower risk of injury to the user.
Frozen in the nose
The usual application for these conventional bulkhead systems was to load frozen foods in the vehicle nose for temperature control by the high-capacity main refrigeration unit. A bulkhead was then placed across the vehicle, and medium temperature products were loaded behind it. Some distributors would place dry groceries in the same compartment; others would install another bulkhead and load groceries in an ambient temperature compartment.
Dividing a cargo space into fore-and-aft compartments works well in terms of temperature control, but requires careful loading techniques and results in relatively slow delivery times. Consider the problems of making multiple delivery stops with a trailer divided into two or three compartments. One purpose of multi-temp equipment is to make one-stop delivery possible, meaning that the driver must remove product from all compartments to complete a delivery. In general, the driver can deliver medium-temperature products and dry groceries through the rear door. For delivery to restaurants, most of which do not have docks, trucks and trailers are equipped with ramps. That still leaves frozen foods in the nose behind a bulkhead that probably has product stacked against it.
At big supermarkets where delivery often involves dropping an entire trailer load and picking up an empty trailer, this does not present a problem. The load is pulled from the trailer through the rear door across the store dock — first the groceries and medium temperature products, followed by the frozen foods.
High stop count
Foodservice distributors face a different delivery reality. Unless the load is configured in such a way that early deliveries create a path to a door through the bulkhead, the driver is left no choice but to access frozen foods through a door in the vehicle sidewall. The International Foodservice Distributors Association says that typical foodservice routes average 14 stops per day with about 55 cases delivered at each stop. In general, about 30% of that volume is frozen foods. If a normal delivery hand truck can carry seven cases, the driver moves six loads out the rear door and down the ramp. That leaves an average of three hand truck loads of frozen foods to complete the delivery. If the driver must use a side door to reach the frozen food compartment, that means climbing up the steps under the door 30 to 40 times a day, each climb an opportunity to fall or drop product.
About 15 years ago, foodservice distributors and equipment vendors began looking for a better way to unload trucks and trailers. Using a side door is a time-consuming process that ties up driver and restaurant personnel. Moving all product through the rear door was seen as a faster, safer, more productive alternative. Among the first of these was a specialized vehicle built for Sysco Corporation by Kidron Inc, using compartment dividers from F/G Products and refrigeration by Thermo King.
Kidron built a unit it called an adjustable compartmentalized multi-temperature trailer. It used a conventional multi-temp Thermo King refrigeration unit with remote evaporators. To allow all unloading through the rear door, the trailer was divided into two long, narrow compartments by dividing it down the middle with a series of longitudinal, 34-inch-wide bulkhead panels. To ensure proper airflow to and from the evaporators, the entire refrigeration system was enclosed above a false ceiling. The result was a rather claustrophobic-feeling trailer with a low ceiling and compartments just wide enough for a single pallet and pallet jack.
Rapid product development
The idea was one of those overnight success stories built on years of hard work and followed by rapid development. Soon, every bulkhead vendor had a line of center partitions. Refrigeration unit manufacturers redesigned their remote evaporators, making them more compact, less susceptible to damage by loading crews, and giving them more capacity than earlier models. These new evaporators produce high-volume airflow, eliminating the need for false ceilings to ensure proper air circulation.
In the United Kingdom, where many perishable deliveries are made on small wheeled carts, trailers were designed with two long partitions dividing the cargo space into three lanes. To refrigerate these narrow compartments, Carrier Transicold and Thermo King designed remote evaporators that could cool a trailer split in half, a trailer split into three lanes, or a one-third/two-thirds split. For trailers intended for constant center partition splits, Thermo King has a nose-mount refrigeration unit with the evaporator section split into two sections so that it can cool two compartments without a remote evaporator.
Center partitions offer great flexibility for compartment size and configuration. Although most deliveries can be made through the rear door, many foodservice fleets have gone back to using a side door. As customers have become more sensitive to delivery temperature and other food safety issues, distributors have moved toward three positive temperature zones in trailers. In general, this results in a compartment in the nose of the vehicle that takes up the full width with two narrow compartments behind it. Those two narrow compartments can be unloaded through the rear door, but the front compartment still requires unloading through a side door.
While the new remote evaporators may be relatively immune to loading damage, the center partitions are not. Sitting unprotected in the middle of the trailer, the rearmost panel in a partition is sure to be hit with pallets as product is loaded. Every bulkhead and partition vendor has developed damage-resistant panel edges that can be replaced easily. In addition, vendors have worked hard to develop easy-to-clean partitions, many of which are made from foodgrade composite plastic sheathing.
Center partitions now are so common in foodservice applications that they constitute the industry standard compared with what once was called a conventional bulkhead system dividing a trailer into two or three horizontal compartments. Every trailer and truck body builder offers center partitions, and every bulkhead vendor supplies them.
