WHITE PAPER: THE BELT DISHWASHER

Together with conveyor dishwashers, belt machines are considered automatic (or “tunnel”) solutions that allow the washing of large volumes of dishes. How are conveyor dishwashers made and how do they work? In this technical article, we take a closer look at the characteristics of these large dishwashers.

Main features of conveyor dishwashers

The operating principle is similar to that of towing machines, with the exception that the plates are transported, as the name suggests, by a conveyor belt. The dishes are placed by one or two operators on the conveyor; this brings them inside the machine where they are washed and possibly dried; then they arrive at the unloading area where they are collected thanks to a constant supervision of operators.

These are very large machines and the largest models can measure up to 8-10 meters in length. They have a structure in AISI 304 and AISI 316 stainless steel with modular construction and, depending on their size and complexity, they can be composed of:

  1. loading area (dirty dishes)
  2. pre-wash
  3. one or more washing modules
  4. Flushing
  5. (possibly) drying
  6. unloading area (clean dishes)
Figure 1: Example of a 6200 mm long belt dishwasher (Elframo model ENR 7200, without drying function)

The belt dishwashers are designed to wash a greater number of dishes (productivity> 2,500 dishes / hour, with peaks of up to 20,000 dishes / hour).

The belt machines are intended for large canteens of companies, schools, hospitals, hotels or ships, where there is a constant and continuous need to wash large volumes of dishes. The belt dishwashers are also suitable for washing other types of objects such as trays, pans, pans, crates or containers.

Careful analysis is required to select the correct model of conveyor dishwasher: the customer is required to evaluate the demand for dishes to be washed at the “peak” time, not the average value. It is also advisable to consider a safety margin as the loading operators may not fill all the available slots of the belt.

Although these washing systems are very expensive, the investment pays off in a short time: it has been shown [1] that a conveyor dishwasher allows to optimize the consumption of water and detergent, and the operating costs related to the washing activity (fewer resources used in the same activity and less time compared to traditional manual washing).

How a conveyor dishwasher is made

Below are the main features of this type of dishwasher.

Conveyor belt – The conveyor belt is made to advance slowly, with different speeds, by a motor located at the end of the machine. The width of the conveyor belt is about 500 mm, but for large machines it can even reach 1,500 mm. For each object to be transported (plates, trays, containers, etc.) a special belt is developed with ad-hoc shaped links, these are separated from each other by a distance (pitch) of about 50 mm or 60 mm.

Splash guards – The splash guards help to divide the various areas of the dishwasher, avoiding, for example, that the water used for washing can end up in the rinsing area, contaminating it, or that the heat inside the dishwasher is dispersed into the environment.

Hydraulic system – Below the conveyor belt there are large tanks that contain the water which is then sucked by the pumps; there are also boilers with electric resistances that heat the water for the final rinse. The heating power can even reach a few tens of kW: it is, therefore, important to size the electrical system accordingly.

Washing arms – The washing arms spray the water on the dishes thanks to the nozzles. They can be removed, inspected and cleaned. Pumps, in the lower area of ​​the dishwasher, ensure sufficient water flow and pressure for washing.

There are, then, other distinctive elements of these solutions, such as:

  • The power supply by electricity (with electric heating elements), or, more rarely, by steam (where a heat exchanger allows the transfer of the same from the steam to the washing water); the latter solution is often adopted in the hospital sector, in the food sector or in canteens where there are boilers and steam systems.
  • The control electronics, which consists of various monitoring sensors and parameters to be selected, including, for example, the belt speed.
  • Specific drying systems for each object to be washed (eg dishes, basins, crates). Many efforts have been made by dishwasher manufacturers on this supplementary system to improve its energy efficiency, as it appears to be an energy-consuming element.
  • The limit switch, which blocks the belt every time the plates reach the end of the unloading section, until they are removed by the unloading operator. Also, whenever the inspection doors are opened, the pumps and the belt stop.
  • The extraction hoods or heat recovery systems from hot and humid air, with the function of reducing energy consumption and improving the quality of the surrounding air. These machines produce a lot of heat and humidity and the ventilation of the room in which they are located can be difficult. It may be necessary to vent and replace the air in the room up to six times per hour.
Figure 2: Inner workings of an Elframo belt dishwasher

Curiosity: dishwashers that… fly!

In English, these machines are called “flight-type dishwashers“. The most accredited theory, which explains the origins of this name, is that there is a similarity between the dishwasher and the airport: the dishes pass through the machine in a straight line as on a landing strip, they “land” on it dirty and “take flight” clean.

Finally, a curiosity about the belt dishwashers installed in prisons: these are deliberately built with anti-theft and anti-tampering features for safety reasons.

Elframo belt dishwashers

Elframo has developed the ENR line to meet all productivity needs, from 2,000 to 7,200 plates / hour, with various accessories.

Do you need more information? Contact our sales department and we will be able to help you in choosing the right dishwasher for you, also developing tailor-made solutions according to your needs.

Bibliography: Katsigris C. and Thomas C., “Design and equipment for restaurant and foodservice – a management view”, third edition, 2009, John Wiley & Sons