Rack conveyor dishwasher is the third member in commercial dishwashers’ family; this type has larger capacity than the two previous types, suitable for large food service systems such as hotels, hospitals, restaurants, prisons, etc.The most simple rack conveyor dishwasher is as shown in Fig.16.2.7, in this type dishes are loaded into a plastic rack (Fig.16.2.8), rack is then loaded into the machine, received by a motor operated belt conveyor, passing through washing zone(s) followed by rinsing & disinfection zone(s).
Fig.16.2.7 Rack conveyor dishwasher and accessories – DIHR – ITALY
Fig.16.2.8 Dishwasher rack – Plasti-Bac – Belgium
Conveyor speed is adjusted as to allow sufficient time for washing, rinsing & disinfection.
Each zone is separated by plastic curtains and has its own set of nozzles. Conveyor dishwasher can be provided with one or more zones & tanks (Fig.16.2.9) such as;
- Pre-wash zone, (zone No 1).
- First wash zone, (zone No 2).
- Second (reinforced) wash zone, (zone No 3).
- Pre-rinse zone, (zone No 5).
- Final rinse & disinfection zone, (zone No 6).
In addition, some optional accessories can be added (Fig.16.2.9) such as;
- Dish dryer: To dry dishes through forced hot air coming from an electric extract fan & heater, (zone No 7).
- Steam condenser: To reduce steam in surrounding washing area, steam is extracted by an electric fan, passes through cold water coil to convert it into water. Water can be directed to drain point or recycled for water save. Removal of hot steam also reduces air conditioning load for washing area.
- Heat recovery unit: This device is also called Economizer or Heat exchanger. Its function is heat incoming water by hot air & steam extracted from the dishwasher. This process has two benefits which are saving part of boiler power by increasing boiler feeding water temperature, in addition, absorbing of air & steam heat prevents overheating of surrounding washing area which reduces air conditioning load, (zone No 4).
Fig.16.2.9 shows also multi water tanks & pumps which allow re-circulation of water, e.g. final rinse water can be used for pre-rinse, washing water can be used for pre-wash, etc. Water & energy saving are essential factors for selecting dishwashers.
Rack conveyor dishwashers can be also provided with Photo cell (eye sensor) to stop the machine automatically in no dishes inside the rack which saves water & energy. Rack conveyor dishwashers can be arranged with different loading & unloading positions as shown in Fig.16.2.10.
In addition to electric heating, some manufacturers can provide dishwashers with steam (if central source is available) or gas heating
Fig.16.2.9 Rack conveyor dishwasher zones – DIHR – ITALY
As shown in Fig.16.2.9, a Rack conveyor dishwasher with the following features; stainless steel construction, stainless steel tanks with no internal seams to ensure perfect cleaning, electric water heating, 400 Volts power supply, insulated door system to improve working environment conditions, adjustable stainless steel feet, self-cleaning pump system (when the pre-wash and main wash tanks are emptied, the pumps are also automatically emptied, machine is provided with; pre-washing – first washing – reinforced washing – reinforced double rinse, splash guard, water pressure reducer. Machine is suitable for 500 x 500 mm racks with useful height of 400 mm, washing capacity of 180/240 racks/hr (water supply temperature of 55°C – add 12 KW heating boiler for water at 15°C), machine has the following technical data:
|Pump capacity||550 Lit/min||Belt conveyor motor||0.22 KW|
|Pump power||1.1 KW||Inlet water pressure||1.5 to 4 bars|
|Tank capacity||70 Lit||Total electric power||47 KW|
|Pump capacity||550 Lit/min||Dish dryer|
|Pump power||1.1 KW||Length||600 mm|
|Tank capacity||70 Lit||Fan capacity||1000 m3/hr|
|Tank heating||6 KW||Fan power||0.75 KW|
|Reinforced washing||Electric heater||12 KW|
|Pump capacity||650 Lit/min||Steam condenser|
|Pump power||2 KW||Fan capacity||350 m3/hr|
|Tank capacity||110 Lit||Fan power||0.18 KW|
|Tank heating||12 KW||Heat recovery unit|
|Double rinsing||Fan capacity||350 m3/hr|
|Water consumption||Fan power||Fan power||0.18 KW|
|Heating power||2 x 12 KW|
|Boiler capacity||2 x 10 Lit|
|Tank capacity||10 Lit|
|Pump capacity||85 Lit/min|
|Pump power||0.1 KW|
Machine total weight is 520 kg, dims 3200 x 750 x 1770/2015 mm height, optionally can be provided with; (double skin – insulated tanks – speed controller – booster pump – detergent economizer – inlet/exit tables (see dishwasher tables) – HACCP monitoring – dish dryer – steam condenser), machine can also be provided optionally with heat recovery unit model TR 98 to heat cold water up to 45 °C and save around 12 KW or model TR 99 to heat cold water up to 65 °C and save around 20 KW ), machine model (AX 440), manufactured by “Dihr” – Italy.
Flight type dishwasher:
Flight type dishwasher is similar to rack conveyor dishwasher and also moves dishes with motorized belt conveyor, but the difference between rack conveyor & flight type, that flight type does not use dish rack, where dishes are directly arranged on the toothed belt, see Fig.16.2.11. Flight type has the largest capacities in commercial dishwashing machines, suitable for large catering systems such as airport catering systems, army catering systems, industrial systems, etc. Flight dishwashers can be provided with all features & accessories similar to rack conveyor dishwasher.
Fig.16.2.10 Flight type dishwasher – DIHR – ITALY
Fig.16.2.11 Flight type dishwasher inlet – DIHR – ITAL