Foodservice Equipment Reports

Latest Rackless Warewashers Take Flight

If you’re serving a few thousand meals a day, but you’re sending them out in paper bags or on disposables, flight-type warewashers aren’t for you. You’re probably fine with a door-type in back somewhere to wash a few utensils and some pots and pans. But if you serve as many as 600 or more meals an hour during a rush using tableware, flatware and glassware, and a rack conveyor isn’t enough, a big, rackless flight-type might be your answer.

Flight-type machines, especially the largest of them, are the big rigs, the eighteen-wheelers of the scullery. These are big, honkin’ machines, and the bigger ones are capable of washing up to 20,000 dishes per hour or more. As a group, they take up almost as much space as a big rig, too, starting at about 9’ and stretching from there up to 54’ or so.

If you’re in that volume ballpark, flight types offer plenty of advantages over smaller warewashers. Rackless machines generally use less water per piece than conveyor machines with racks. Another advantage of going rackless is that flight-type machines can accommodate a wider variety of odd-shaped kitchenware. Most can take all but your tallest stockpots. (Some machines are specifically designed for those, too.)

As for advances? In recent years flight-type warewashers have shared in, and in many case led, the gains in water and energy efficiency. Compared to the latest versions, the flight types we reviewed in 2001 drank water like a Boston Marathon runner at the 25-mile mark.

And there’s a wider variety of flight-types available now. The biggest of these rigs are designed for huge operations—casinos, hospitals, prisons, convention hotels, and so forth. But there’s a class of smaller flight-type machines, the smallest of which are actually competitive with large conveyor rack machines. So, if you have a large operation, when might you consider moving up to a rackless machine?

When And Where?

As mentioned above, the two biggest considerations are volume and space. As with any piece of equipment, from ice machine to oven, you need to figure capacity based on your peak volume. Too many operations make the mistake of sizing a piece of equipment to meet average demand, so it’s never able to keep up when the rush hits.

Figure how many washable items per customer—tableware, flatware, glasses, etc.—and go from there. If your peak volume is around 600 meals an hour, and the average place setting is about 14 pieces, you’re talking more than 8,000 pieces per hour. That’s just about where the capacity of flight-type machines starts.

Space, typically at a premium in any foodservice operation, is the other deciding factor in going to rackless machines. And you can bet the dishroom is low on your executive chef’s priority list when it comes to kitchen design and layout. There’s a lot of customization in the category, though, so most manufacturers can squeeze machines into your space using standard sections with a few tweaks.

Tanks, for example, typically are built in 36” or 48” sections. A 3-tank machine is 9’ long without loading or unloading tables. Say you want a 12’ machine, but you only have space for an 11-footer. A manufacturer might use a standard 36” tank for the pre-wash, for example, and 48” tanks for wash and rinse.

Staging areas for loading and unloading have to be factored in. Most manufacturers recommend you have at least 3’of space on the load side and a minimum of 8’ to unload. In a straight-line configuration, you’re looking at a minimum of 20’. While you need at least some straight space tacked onto both ends of a rackless machine—say 3’ or 4’—the rest of the staging areas can be turned ninety degrees, if necessary.

You’ll also need enough room to get dishes in and out of the dish room. It doesn’t do you any good to have a machine that washes 12,000 pieces an hour if you can only move half that many in and out of your dishroom in the same time. You’ll need floor space for dish carts and whatnot, and room to maneuver them.

Biggest Advances

The biggest changes in flight-type machines since we last wrote about them are in three areas: water efficiency, energy efficiency and accessibility.

Today’s machines are a lot more water efficient due to improved design of the nozzles and spray arms in the fresh-water final rinse tank. All dishwashers are governed by NSF Int’l. specs that say the final rinse cycle in dish machines must accomplish two things.

First, it must sanitize the dishware by bringing the surface temperature up to 160° F for at least 15 seconds. That typically means the water temp at the spray manifold is usually somewhere around 180° F. Any cooler and the dishware won’t get hot enough to get sanitized. Any hotter and you’re either wasting energy or turning the water to steam. Which brings us to the second point.

The final rinse must remove all traces of chemicals used to get the dishware clean in the first place. You don’t want any traces of detergent doing the same number on your customers’ stomachs that the chemicals do on your dishes. So you need enough hot water (steam obviously won’t get the job done) to heat and rinse your dishes.

Not that long ago, these machines used as much as 425 gals./hr. or more in the final rinse tank. Manufacturers have tweaked the spray pattern on their final rinse nozzles to limit the amount of water needed to do the job. These days, typical machines in the capacity range of 12,000 to 14,000 dishes per hour use around 140 gph. One new washer uses a miserly 84 gph while cleaning up to 13,000 dishes per hour. The same model uses only 72 gals. to clean about 10,000 dishes. Another company’s machine can clean up to 8,700 dishes per hour using only 65 gph final rinse water.

Save water, particularly hot water, and guess what else you save? You got it—energy. But reducing the amount of hot water in the final rinse tank isn’t the only way manufacturers have found to improve energy efficiency.

In addition to using less hot water, manufacturers have added heat exchangers to many models, either as an option or standard equipment. These systems use exhaust heat to raise incoming fresh water temperature anywhere from 50° to 70° F.

One maker says its heat exchanger will raise incoming water temp from an ambient 60° F up to 110° F. Another claims its machine can heat inlet water that’s 55° F up to 128° F. That eliminates the need for a tank heater in the final rinse compartment. All you need is a booster heater to bump up the final rinse temp to 180° F.

Most manufacturers also have added insulation to their dish machines’ doors as well as top and sides. Better insulation equals better heat retention, resulting in energy savings. Some equipment makers are foaming as much as 2” of insulation between interior and exterior stainless walls. The insulation has the added advantage of damping dish-machine noise.

The move to electronically commutated motors (ECMs) also has added to energy savings. These big boys have a lot of them—a pump motor for each tank, so three or four, plus one for the conveyor belt. Pump motors are typically in the range of 1 to 3 hp for the pre-wash tank, 3 hp for the wash and rinse tanks, 1/5 to ¼ hp for the auxiliary rinse (if it has one), and about ½ hp for the belt drive. Add on optional blower motors for a drying chamber and another motor for an exhaust vent fan, and the energy use climbs, so efficient motors help.

One manufacturer goes so far as to enclose pump motors to protect them from water spray during dishroom clean-up. The enclosed motors are fan-cooled. Pumps themselves are typically constructed of stainless with stainless impellers and are designed to be self-draining, reducing the possibility of corrosion and extending their service life.

That last big change, accessibility, is a result of manufacturers designing machines with larger doors. More accessible tanks means machines are easier to clean (and service, if necessary). Some models even come with interior lights, the thought being you can’t clean it if you can’t see it.

The Basic Beast

Typical 3-tank machines consist of a pre-wash tank, wash tank and rinse tank. Add on a final rinse tank to get a 4-tank rig. Manufacturers, of course, will give you any configuration you need, adding another wash tank in the middle if you want, or a blower on the end for drying.

Heat also comes in just about any configuration you want including electric, injection steam, steam coil, and even a few gas units. If you already have a steam plant, steam’s a natural way to go, but many of you will opt for electric units.

Recognize that you may need to bring in new electric service for the dishroom when you shift to a bigger rig. Tank heaters vary in size depending on the size of the tank (typically around 36 to 40 gals.) and the maker. Total draw ranges from about 25kW to 60kW depending on the model.

Booster heaters for the fresh water final rinse also can be electric, steam or gas. Some models have boosters built in. Others offer the booster as an option. Electric booster heaters usually run about 15kW.

Most manufacturers offer you a choice of conveyor belts. To start off, you have your pick of slim-line units with belts around 23” wide or the more standard machines with belts about 29” or 30” wide.  

Belts themselves are offered in a choice of polypropylene or stainless. Peg patterns vary, too. If you’re loading mostly tableware, a pattern with spacing of 2” to 2½” will give you a lot of capacity. For larger items, like a lot of cookware, you may want to choose a belt pattern with 3” spacing. Belts also are available in several other configurations such as flat for cutlery or special pegs for large cookware.

Most models offer you a choice of belt speed so you can slow the machine down to wash particularly dirty loads like cookware. Some machines only have two or three speeds. Others offer variable-speed belts, but the range on all will usually be between about 4’/min. and around 9’/min. Remember that the maximum speed is governed by the NSF Int’l. requirement for sanitizing. Too fast, and the dishes won’t get hot enough in the final rinse.

Almost all models have a limit switch that stops the belt when dishes reach the end if no one’s there to catch them and unload the machine. Which begs the question of how many employees it takes to operate a flight machine. A lot of people will say you need two people, one to load and one to catch. If you’re operating a really big rig, one person can load a lot of dishes and when the belt stops, go catch what’s been loaded.

That raises another interesting topic. Several models offer an energy-saver sensor that only turns on the final rinse spray when there are dishes in the machine.

Other features like automatic tank fill, low-water warning, temperature-limit switch, door-safety switches and a conveyor-reversing/cutoff switch are common to most models.

A Lot of Hot Air?

Another factor to consider is ventilation. Dish rooms are hot and humid enough as they are. But big rigs don’t have to add to the problem. Models with heat-recovery systems divert what would have been waste heat, channeling it into preheating incoming water instead of adding to the heat and humidity in the room.

Nevertheless, flight machines do exhaust hot air, and most will require about 750 to 800 cfm of makeup air. Some manufacturers have made exhausting their machines relatively easy by designing them with a single-point vent connection. Others still have multiple vents, so do your homework in the planning stages as you configure where the machine will go in your dish room and how you’ll handle exhaust.

Don’t forget that if you add a drying chamber (or two) on the end of your machine with blowers, you’ll probably increase your make-up air requirements to more than 1,000 cfm.

Command And Control

Manufacturers are split on controls. Some now offer electronic controls that give you the ability to do things like monitor wash and rinse temperatures from a computer for HACCP documentation.

Others say the hot, humid conditions of the dishroom are too extreme for electronics, so they still offer electro-mechanical controls. An added benefit, they say, is that many components are standard, not proprietary, and available from electric supply companies. That can make service and repair easier in some cases.

All manufacturers attempt to place control panels where they’ll least likely be subjected to water intrusion (especially from zealous employees hosing down the machine at the end of a shift). They’ve also made them as water-resistant as possible.

As sophisticated as a machine’s controls may be, electronic or electro-mechanical, manufacturers have made operation in most cases as simple as a single on-off switch. Once the machine is turned on, it fills automatically, brings the water up to temperature, and dispenses chemicals as needed.

Belt controls are usually separate with a start-stop switch located at the load end and sometimes the unload end also. Belt-speed control is usually located on the control panel, with the aforementioned safety conveyor cutoff switch at the end of the belt.

Along with designing spray arms and nozzles to clean more effectively and efficiently, manufacturers have spent a lot of time on designs that limit clogging and are easy to clean. Toward that end, spray arms now are generally easy to remove and clean, and many are constructed in such a way that parts only fit together one way, ensuring that employees reassemble them correctly.

Scrap baskets also are larger and better designed than they used to be, again making access, removal and cleaning easier than ever.

One manufacturer even has a special unit that can be added to the front of the machine that diverts some clean water into the prewash and wash tanks to reduce detergent use, prerinses the dishes before they enter the prewash tank to reduce the need for scrapping, and uses cyclonic separators to remove that debris from the tank water.

Most manufacturers offer a wide range of features and options not mentioned here, usually providing enough flexibility to meet your needs. If you’ve been considering a step up to big rigs based on your volume requirements, you may be pleasantly surprised by the performance and efficiency of today’s flight machines.

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