White paper: Rack-type dishwashing machines

White paper: Rack-type dishwashing machines

Rack-type dishwashers are considered automatic (or «tunnel») solutions, such as flight dishwashers, but they are smaller and more versatile. These special dishwashers allow the washing of a large number of baskets. How rack conveyor dishwashing machines are made and how do they work? Let’s see in this white paper an overview of the main features of these large dishwashers.

Main features of rack dishwashers

Traditionally, the first washing phase is the one performed by the operator and takes place on the prewashing table completed with a sink. Here the first coarse removal of the dirt takes place. Then dishes are placed by the operator in standard size baskets (size 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 area to drying zone (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 washing/rinsing tank with a length of one meter, to the largest ones that can have up to three washing tanks and with a length that can reach over 3.5 meters. Rack dishwashers are often equipped with accessories, such as straight rollers, curves and service tables or sink tables that further increase their overall length.

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

  1. loading area (dirty dishes);
  2. pre-wash zone;
  3. one or more washing modules;
  4. rinsing module;
  5. drying system (if present);
  6. unloading area (clean dishes).

Fig. 1: Example of a rack conveyor dishwasher machine with rolling tables and sorting table (Elframo – ATR model, with drying system)

The rack conveyor dishwashers are designed to manage a large number of dishes: productivity ranges, depending on the model, between about 50 and 300 racks/hour, i.e. between 800 and 5.400 dishes/hour (each rack accommodates 16/18 dishes). Conveyor dishwashing machines are therefore designed for large restaurants, canteens, schools, hospitals, hotels or cruise ships. The rack-type dishwashers allow you to wash glasses, cutlery, dishes and trays, simply changing the basket. In an industrial kitchen, therefore, there are different kinds of baskets depending on the different types of objects to be washed.

A rack-type dishwasher is the best solution when you need a high working flexibility: the presence of roller conveyors, the possibility of changing the basket and the wide choice of modules make rack dishwasher a more versatile system than the flight-type dishwashing machines.

How a rack-type dishwasher is made

Below 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; then, it is pumped into the washing arms. Below the tanks, there are some boilers with electric heating elements that heat-up the water for the final rinse. The heating power can even reach a few tens of kW.

Conveyor mechanism – The basket is advanced by a pawl-rack system. Inside the dishwasher, a long rod (or two placed in parallel), called «conveyor rod«, that moves alternately back and forth, thanks to a gearmotor on which an eccentric is mounted. Several tilting teeth called «pawls» are connected to the rod: they hook to the bottom of the basket, which has a grid structure and acts as a rack, and push it forward every time the 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 system – 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.

Economizer – It is a system that allows 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 into the 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 panel – The control of these dishwashers can be electromechanical or a thanks specific electronics, even with touch-screen panels.

Fig.2: Inside detail of an Elframo rack conveyor dishwasher

Elframo rack conveyor dishwashing machines

Elframo has developed the ETS 16 model for limited space requirements, the ETE range for common works and the ETR line that allows higher flexibility and modularity. Finally, there is also the new ATR line, which differs from the other models for the presence of an advanced electronic controls based on touch screen.

Do you need more information?

Contact us and we will be glad to support you in choosing the dishwasher model that best suits your needs: our internal R&D team is ready to design your customized solution.