Transport crates for baked goods do not appear to differ much at first sight. They only vary in color, weight and height. However, when it comes to cleaning the crates, the situation is very different. This means that the expectations on a washing plant are many and varied.
For crates and baking trays: continuous washing system DLWA 250 BACK Highline with blow-off zone for fast drying. Right: Detailed view of the nozzle arms
Depending on the available space and the environment, installation, operation and maintenance can become a real challenge. This is where technical know-how and individual solutions are required, as provided by Mohn GmbH in Meinerzhagen throughout Europe. The washing systems not only clean transport crates, but also various types of containers and even pallets. Special systems are offered for container trolleys and rack trolleys.
The company believes that individual customer support from the first consultation to installation and commissioning is the key to success. Numerous parameters play a role here. The first step is to determine how many containers per hour or per day need to be cleaned. Capacities of the washing lines can vary from 250 crates up to 3,000 crates per hour. Solutions are also worked out for different types of crates or pallets, tailored to the specific requirements.
Another decisive factor, for example, is the degree of pollution, in deciding whether to install a single or multi-tank system. And last but not least, the washing system must be easy and quick to clean. To ensure this, Mohn builds the machine housings completely in one piece and fully welded. The washing tunnels are equipped with a long active washing zone, the length of which varies depending on the design and washing performance. In addition, the washing tunnels are double-walled with 30 mm thick insulation. This not only contributes to an extended service life and the prevention of heat loss, but also to a reduction in noise levels during the washing process. The machine housing and stainless steel control cabinet are both designed hygenically.
Other factors that have an effect in practice are generously dimensioned tanks and powerful washing pumps that use maximum mechanical forces with high circulation and pressure to deal with the dirt. The strength of the washing pump depends on the number of containers or type of trays to be cleaned and their degree of soiling. The “standard” 250-BACK washing machine (up to 250 containers or 150 trays per hour), for example, operates with a stainless steel centrifugal pump with 4 kW output at a circulation of 1,000 l/min and 2 bar washing pressure, distributed over 50 stainless steel flat-jet nozzles.
The stainless steel washing nozzles with wide passages ensure thorough cleaning and do not collect dirt due to self-cleaning. An external box filter ensures that large quantities of dirt are absorbed and can also be cleaned during operation. A further addition to improve performance is the simple height adjustment of the hold-down device for different wash items. According to the company, the design engineers have created a technical trick in the construction and arrangement of the jet nozzles. The nozzle assemblies can be removed and completely cleaned in a few simple steps. They can then only be reinstalled in the optimum position. This has the advantage that the washing pattern cannot be changed. A well-thought-out measure against unnecessary water carry-over from the washing tunnel is the sloping passage of the Euronorm containers. Ergonomics were also taken into account in the design. For example, the maintenance doors were designed so that all parts of the system are easily accessible and simple to clean. The installation of a cold-water pre-spray is optional to prevent coarse dirt or protein ingress going into the washing tunnel. For fast drying, insulated blow-off tunnels or centrifugal drying modules can be added as a supplement.
Continuous washing system for a bakery
For a manufacturer from the baking industry, Mohn implemented a continuous washing system, designed to clean both crates and baking trays. The basis of the installation is a crate washer type DLWA 250 Highline, which is available as a standard “BACK version” with tunnel dimensions designed for useage in bakeries.
Their hourly output is approx. 250 to 300 crates or 120 to 150 baking trays. The tunnel passage width is 600 mm. Crates and baskets are conveyed through the washing plant in a longitudinal direction. The tunnel passage height is suitable for low and high crates (e.g. with a height of 400 or 450 mm, for delivery to the stores).
The 600 mm pass-through width is specially designed for the 980 x 580 mm baking trays available in the bakery. Special lateral hold-down devices fix the baking trays (shown in the tunnel inlet in the picture above) so that they are not pushed out of the guide by the water pressure.
A large outer box filter collects coarse dirt such as seeds or cake residues. The dirt is flushed into the external filter and can be easily cleaned, even during operation.
Depending on the inlet temperature, the tank has a 20 or 30 kW heating system (electric/steam/thermal oil, depending on requirements) to effectively remove even baked-on dirt. For the bakery, a 20 kW heating system was installed in the main wash. The washing temperature here is around 55 °C. The rinse zone works with a 10 kW continuous flow heater.
After a fresh water rinse, in which any excess cleaning agent is removed – the water runs into the tank via a cascade system and floating dirt is washed out via the filter – the crates and sheets then pass through a neutral zone into the blow-off zone. Here, two high-pressure 5kW fans, blow off the washed items from all sides. The total length of the system with blow-off is around 8,000 mm.
The DLWA 250 BACK Highline