Conveyor dishwashers are considered automatic (or “tunnel”) solutions, such as belt conveyors; unlike the latter, however, they are smaller and more versatile. These special dishwashers allow the washing of a large number of baskets. But how are rack dishwashers made and how do they work? Let’s see in this technical article the characteristics of these large dishwashers.

Main features of rack conveyor dishwashers

Traditionally, the first washing phase is the one performed by the operator and takes place on the clearing sink. This is where the first coarse removal of dirt from the dishes takes place. Subsequently, the dishes are placed by the operator on standard size baskets 500 × 500 mm. Once the basket is brought close to the dishwasher entrance, it is hooked and “pulled” along the entire length of the tunnel. In this way, the basket runs through all the dishwasher modules, from prewashing to drying (if present), up to the unloading area, where the basket with the clean dishes is removed.

Depending on the model, the rack-type dishwashers can assume different configurations: from the smallest, with a single wash / rinse tank and just over a meter long, to the largest that can have up to three washing tanks and whose length can reach over 3.5 meters. Trailed dishwashers are often equipped with accessories, such as straight roller conveyors, curves and clearing sinks that further increase their overall length.

The rack type dishwasher structure is in AISI 304 and AISI 316 stainless steel with modular construction. Depending on its size and complexity, it can be composed of:

  1. loading area (dirty dishes);
  2. pre-wash;
  3. one or more washing modules;
  4. Flushing;
  5. drying (if any);
  6. unloading area (clean dishes).
Figure 1: Example of a pass-through dishwasher with sink unit and roller conveyors (Elframo, ATR model, with drying function)

The rack conveyor dishwashers are designed to wash a large number of dishes: the productivity ranges, depending on the model, between about 50 and 300 racks / hour, i.e. between 800 and 5400 dishes / hour (each rack accommodates 16/18 dishes) . Conveyor dishwashers are therefore intended for large restaurants, canteens, schools, hospitals, hotels or cruise ships. The rack conveyor dishwashers allow you to wash glasses, cutlery, flat or soup plates and trays, simply by changing the basket. In an industrial kitchen, therefore, there are several types of basket depending on the different types of objects to be washed.

A rack conveyor dishwasher is the ideal solution when you want to achieve greater working flexibility: the presence of roller conveyors, the ability to change the basket and the wide choice of modules make rack-type dishwashers a more versatile system than belt-type dishwashers.

How a rack conveyor dishwasher is made

Below are the main features of this type of dishwasher.

Hydraulic system – Below the sliding surface of the baskets, there are heated tanks containing the water that is sucked by the pumps. Before being sucked in, the water passes through grids that filter it, retaining the largest residues; subsequently, it is conveyed into the washing arms. Below the tanks, there are some boilers with electric resistances that heat the water for the final rinse. The heating power can even reach a few tens of kW.

Towing mechanism – The basket is advanced by a pawl-rack system. Inside the dishwasher, a long rod (or two put in parallel), called a “tow rod”, moves alternately back and forth, thanks to a gear motor on which an eccentric is mounted. Several tilting teeth called “pawls” are connected to the rod: these hook to the bottom of the basket, which has a grid structure and acts as a rack, and push it forward every time the tow rod advances linearly.

Washing arms – The washing arms spray hot water and detergent on the dishes thanks to the adjustable nozzles, positioned above and below the basket. The nozzles are removable, so they can be inspected and cleaned.

Drying – The drying module, if present, consists of a fan that blows hot air onto the racks that have already completed the washing and rinsing phases. The module can be linear or at a 90 ° angle in order to optimize the available space, always guaranteeing the best performance.

The economizer – It is a system that allows you to significantly increase the energy efficiency of the system. Each module of the machine, in which the economizer is present, is activated only when the basket enters the aforementioned module and is deactivated when it comes out. In this way, electricity and water are not wasted in the absence of baskets in the module.

Control – The control of these dishwashers can be electromechanical or with dedicated electronics, even via touch screen panels.

Figure 2: Inner workings of an Elframo pass-through dishwasher

Trailed dishwashers by Elframo

Elframo has developed the ETS 16 model for limited space requirements, the ETE line for common works and the ETR line which allows greater flexibility and modularity. Finally, there is also the new ATR line, which differs from the other models for the presence of electronic controls and control touch screens.

Do you need more information?

Contact us and we will be happy to support you in choosing the dishwasher model that best suits your needs: our internal R&D team is ready to design customized solutions, tailor-made for you.