White paper: Flight-type dishwashers

White paper: Flight-type dishwashers

As the rack conveyor dishwashing machines, flight dishwashers are considered automatic solutions specifically designed for washing large volumes of dishes. How a flight dishwashing machine is made? In this white paper, we take a closer look at the features of these big dishwashers.

Main features

The operating principle is similar to that one of the rack conveyor machines, with the exception that dishes are transported, as suggested by the name, by a conveyor belt. The dishes are placed by one or two operators on the belt that brings them inside the machine where they are washed and possibly dried; then they reach the unloading area where they are collected by operators.

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

  1. loading area (dirty dishes)
  2. pre-wash module
  3. one or more washing areas
  4. rinse module
  5. (if present) drying system
  6. unloading area (clean dishes)
Fig. 1: Example of a 6.200 mm long flight dishwasher (Elframo ENR 7200, without drying)

Flight dishwashers are designed to wash large volumes of dishes (productivity > 2,500 dishes/hour, with peaks of up to 20,000 dishes/hour). These solutions are perfect for large school or company canteens, hospitals, hotels or ships, where there is a constant and continuous need to wash large volumes of dishes. The flight dishwashers are also suitable for washing other types of objects such as trays, basins, pans, crates or containers.

Careful analysis is required to select the correct flight dishwasher model: the customer needs 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 on the belt.

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

How a flight dishwashing machine is made

Below the main dishwasher features.

Conveyor belt – The conveyor belt advances slowly, with different speeds, thanks to a motor placed 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 chain is developed with tailor-made shaped links, that 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 zones of the dishwasher, avoiding, for example, that the water used for washing can enter 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 some boilers with electric heating elements 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 dishwashing machine ensure sufficient water flow and pressure for washing. There are other distinctive elements of these solutions, such as:

  • The electric power supply (with electric heating elements), or, more rarely, with steam (where a heat exchanger allows the heat transfer from the steam to the washing water); the latter solution is often used in the hospital segment, in the food market 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 speed of the belt.
  • Specific drying systems for each object to be washed (e.g. 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 end microswitch, which blocks the belt every time the dishes reach the end of the unloading section, until they are removed by the 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 air in the washing area. These machines produce a lot of heat and a lot of 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 [1].
Fig. 2: Details of the inside part of an Elframo flight dishwasher

Some curiosities: the dishwashers that…flight!

 As said, 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 [1]. Finally, a curiosity about the flight dishwashers installed in prisons: these are deliberately built with anti-theft and anti-tampering features for safety reasons.

Elframo flight dishwashing machines

Elframo has developed the ENR range to meet all productivity needs, from 2’000 to 7’200 dishes/hour, with a wide range of accessories and additional systems.

Do you need more information? Contact our Sales team, 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 customized solutions, depending on your specific requests.

References

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