All-in-one: a new tray washing plant for Schäfer’s

A new plant made by Kitzinger has been washing trays and peelboards in Schäfer’s Berlin factory since February 2018. Performance, durability and flexibility were decisive aspects for the bakery, but above all the plant was required to make do with little space.

+The requirements catalogue with which Schäfer’s combed the market for suitable candidates was definitely challenging. The machine had to be able to clean 1,100 to 1,300 trays/hour. And any number of different trays, because altogether nearly 20,000 of them in 12 different formats* rotate in the company. It had to be able to cope equally well with other items needing to be washed: cake rings, crates, baskets, molds/pans, dollies and especially PlanB peelboards. “Not entirely straightforward,” according to Works Manager Thomas Drews. “Since in contrast to trays, these boards do not dry nearly so well because they are made of plastic and thus do not absorb heat.” However, the biggest obstacle that had to be overcome was the limited space. “Our existing building had no more than 16 meters of length available for the plant.” There were not many machine constructors who could fit this kind of cleaning performance into the really short size of the available space. The company finally decided in favor of Kitzinger Maschinenbau GmbH in Flensburg.

Special features

Schäfer’s new investment is a tray washing plant of the contino type. It is 13.80 m long, and is thus a whole 2 m shorter than the length specifications. But it’s not an “off-the-peg” machine. Here are a few of its special features:

+ Adjustment of the machine to differently sized trays or boards takes place via two levers. The first lever can be used to vary the machine’s belt width to accommodate the items to be washed. The second level allows the height of the spray-heads to be adjusted so the jet of water can act in an optimum way on the respective item being washed. No motor is needed for this.

+ The nozzle arms can be dismantled without tools.

+ The entire upper part of the machine can be raised. This simplifies cleaning the interior and enables possible malfunctions to be eliminated quickly. The entire interior is to a large extent fabricated with radii, and horizontal surfaces in the machine have been avoided.

+ A drum filter was installed at the bakery’s explicit request.

Schäfer’s in Berlin

Schäfer’s Produktionsgesellschaft mbH in the Mariendorf district of Berlin, also known under its former trading name Thürmann, is a subsidiary of EDEKA Minden-Hannover. The company supplies 411 bake-off stations and 227 branches, 156 of which are located in the checkout zone and 71 are its own specialist shops. A proportion of the sales outlets still trade under the Thürmann name, but are being carefully rebranded as Schäfer’s.

The locations are situated mainly in Berlin, but also in Brandenburg, where the delivery area extends from

Frankfurt-an-der-Oder to Spreewald and Cottbus. As a rule, the locations receive a delivery once a day. Businesses in marginal locations receive a restricted range of baked products consisting of a total of 52 types of bread, 18 kinds of rolls and 66 types of cakes and confectionery. The plant in Berlin occupies a production area of 5,600 m 2 and a total area of 7,000 m 2, where around 270 employees work. The value of its average monthly production is EUR 3.4 million.

Hygiene

It runs like a washing machine drum alongside the cleaning process and sieves solids out of the effluent flow.

+ Particularly quiet blowing-off during the drying process

+ A double-wall design with the interior space insulated against sound and heat emissions

The washing process

The new washing machine runs for 16 hours/day. Loading is manual. One employee puts items in, a second takes them out and a third deals with the internal logistics, i.e. puts the clean trays or boards on dollies back into the production process at specified parking places or supplies the loading employee with replenishments of items to be washed. The “logistician” has plenty to do, because there is not much space in front of and behind the machine. All three operators are employed by an external company. Like the factory cleaning, tray cleaning at the Schäfer’s site in Berlin is also outsourced.

There are various washing programs for boards and trays. As Drews explains: “We run the trays through more slowly than the boards. For boards it’s mainly a question of easily removable residues, dough residues or grains, whereas with trays there are to some extent burnt-on or crème residues.” He says the latter are more stubborn. Trays push through the plant in 3 minutes and 1 second, while trays take 4 minutes. The time for which the water pressure acts, and the drying time, can be increased by reducing the speed. Otherwise the washing process is the same. Washed items that are not clean enough are pushed through a second time. According to Drews: “As far as capacity is concerned, we are currently running at 80%. We could also increase the speed.” So there’s still room for more.

Trays and boards are washed at separate times. After orderpicking the products, which ends at Schäfer’s at around 03:30 hrs., tray-cleaning starts. For a period of seven hours exclusively trays are washed, which pass through the main tunnel in a horizontal position. The water is changed before switching over to boards, to avoid the possibility of fats etc. being carried over onto the plastic surface of the boards.

Data for the tray-washing plant at Schäfer’s, Berlin

Daily operating time: 16 h

Dimensions: 13.80 m x 2.50 m

Electric power consumption: 47 kW

Makeup water temperature: 60°C

Inlet pressure at nozzles: 2 - 6 bar

Makeup water consumption for rinsing: 400 – 500 liters

Operating staff per shift: 3

Items being washed: trays, boards, cake-rings, crates, baskets, molds/pans and dollies

Residual moisture: trays: 0.87 g, boards: 2.1 g

Noise emission: 84 – 85 db(A)

Cleaning the plant takes one hour. The changeover to boards then takes place. Exclusively boards are washed for another seven hours. They push through the machine vertically in a side-tunnel. The upright position simplifies drying. Water is blown off from the side and drains away downwards. This is followed by another machine-cleaning program (1 hour), so as not to “contaminate” the trays in the reverse direction, i.e. with flour and grains. An estimated 7,000 trays and 10,000 boards pass through the plant every day.

A residual moisture level of 0.87 g is achieved on trays, and 2.1 g in the case of boards. These again lie considerably below specifications, since Schäfer’s had defined a residual moisture level of 5 g for the boards. Schäfer’s site in Berlin may possibly say goodbye to handling boards in the foreseeable future, and thus also to washing them. According to Thomas Drews: “The plan in future is for part of the bread roll range to come from Osterweddingen pre-proofed and frozen.”

Heat generation and water consumption

About heat generation: the tray washing plant is heated by steam. No heat is generated in the machine itself. A heat exchanger in a separate room is supplied by a steam boiler. The latter virtually runs the steam into the machine’s water tank, thus heating the water.

About the water: the machine’s water consumption is very low due to its cascade-type use – water from the blow-off area runs into the prewash zone and is discharged from there as overflow liquid – a very small amount, and this is important for the following reason: in the first place, incoming makeup water represents a cost factor, firstly as water and then as wastewater, although the significant costs arise from heating it to the required temperature and due to the additional detergent requirement. Thomas Drews says: “The machine cleans in two zones. There is a prewash zone and a washing zone, followed by a final clear rinse and drying. The machine recycles water internally. We recycle the water back again. Heat energy is not lost, but is used for prewashing instead.” Overall, he says, the “Kitzinger” makes do with

Like a fakir on a bed of nails

Schäfer’s uses PlanB boards to deliver fresh dough pieces to branches. The boards are uncoated. The surface has a grid of microcolumns. These look like many thou sands of tiny pyramids. The dough piece rests on them virtually like “a fakir on a bed of nails” and does not adhere.

around one third less energy compared to a competitor model in another Schäfer’s factory, and he adds: “In my opinion, the results of cleaning are first-class. We take APEX contact plate samples which show that we lie considerably below a significant microbial count.”

Cleaning agents

Two cleaning agents are used: a detergent and a rinse aid. The company also considered that the ability of feed in disinfectant as well if necessary was also important. Because the choice of detergent affects which pumps etc. are used, consultation took place between the cleaning agent manufacturer Calgonit and Kitzinger.

Installation and commissioning

A wall had to be taken out to enable the plant measuring around 13.80 m x 2.50 m to be installed in the existing building. Demolition work, dismantling the old machine and installing the new one, assembly including welding and angle-grinder work to install the drum screen, and finally rebuilding a new wall took just under six weeks. Washing during this time was done elsewhere. Drews says: “Tray washing was undertaken by sister companies. It was a logistical masterpiece, fortunately in a manageable period of time. Considering that the plant has been in place for ten years, the set-up cost fades into the background.” +++ foodtechnology@zeppelin.com

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