If you want to see what accuracy and efficiency can mean in raw materials provision, you might want to pay a visit to Bleiswijk, Netherlands. Zeppelin Systems has been working with the new Hoogvliet bakery there and has delivered a solution that sets itself apart from others in many details.
For example, the temperatures of all raw materials are recorded before they are weighed – this is standard practice in modern production facilities, and then the temperature of the water to be added is calculated from those recorded values. At the Bleiswijk bakery, however, the raw material temperatures are not recorded just whenever, but directly before the dosing process adds ingredients – for example just before the injection nozzle adds flour – and then measurements are taken at up to three different points during dosing. Accurate measurements of this kind, performed at delayed intervals, make it easier and safer to achieve and maintain the target dough temperature, which is regulated by the control system, by means of automatic temperature correction.
Another example is the SPAS conveying screw pool discharge system. In the past, flour was brought from the silos by means of a time-consuming, bulky system of vibration surfaces and valves, stored in buffer containers and then conveyed using screws; now, a compact unit consisting of up to five conveying screws is available to perform this task, including transporting flour from the silo along the same number of separate lines. The SPAS for Hoogvliet was implemented with three conveying screws and a parallel double agitator, which eliminates any product bridging across the discharge outlet. The entire conveying unit is not just significantly slimmer than the old systems, but also much more easily accessible for maintenance operations.
Extensive testing of the mixtures used by Hoogvliet at the Zeppelin Food Technology Center found that, because of the diversity of specific weights among seeds and grains, the homogeneity of a grain mixture tends to be lost when the container or Big Bag containing it is moved. A system was developed to counter this effect: Grain mixtures are delivered to the Bleiswijk bakery in Big Bags and automatically conveyed to the dosing storage hopper as soon as there is sufficient space for the contents of a bag, and once in the storage hopper, a constantly rotating screw homogenizes the mixture again.
The system collects small ingredients from its 1 m³ storage hoppers and weighs them on central weighing scales using secondary containers, accurate to one decimal place, before adding them to the medium ingredients. The small ingredients silos are filled by bag outflow.
As a new batch of dough is due to be produced, the system first separately conveys flour and medium ingredients (with the small ingredients included) to the two weighing containers above the kneader, before releasing them into the kneading bowl after approval. Here, an integrated platform scale allows the system to monitor the manual feeding of particularly sensitive raw materials at the same time or at a later point.
These examples clearly show how this plant optimizes every individual detail. Furthermore, the plant does not merely consist of the solid material preparation elements and the water mixing and dosing unit: Yeast catalysts provided by yeast suppliers and the IP container containing the oil and baking agent mixtures are also included in the Zeppelin control system, the latter even featuring its own temperature control system to ensure that the oils always remain free-flowing.
What makes the entire concept particularly exciting is that it can respond very quickly to changes in demand from the Group’s own supermarkets. Small Hoogvliet vans drive to each store up to four times a day, ensuring that each one is constantly replenished with wonderfully fresh baked goods – and this reliable freshness is central to the supermarket chain’s public image.
Each store must order a minimum baked goods quantity of four loaves. There is also ongoing alignment ensured between the point of sale and baked goods production, as it is entirely possible that considerably more or less of a particular variant will be required. To respond accordingly to this variable demand, the company’s internal IT department is continually optimizing its baking schedule and passing requirements on to the bakery’s process control department. That department in turn optimizes the batch sequence and size, which can be between 80 and 240 kg.
The entire modular control system for the raw materials logistics is based on Siemens Profinet fieldbus systems, with the design incorporating a main or power switch cabinet as well as a range of decentralized switch cabinets. Each of the three lines is equipped with its own decentralized switch cabinet, as are the small and medium ingredients stations. All the relevant on-site command centers are equipped with client PCs so that authorized employees do not need to travel far to enter commands, but can simply make any necessary changes from wherever they are. Each client PC has the same functionality as the command center, provided that the employee can verify their identity. The system also allows for problem-free communication with downstream facilities such as kneaders and checkweighers. The Bleiswijk plant is still quite new, and as such has been designed to permit future growth; while it currently has two large bread production lines with a total capacity of 7,000 loaves per hour and one bread roll production line, which produces 24,000 soft rolls per hour, there is enough space to add two additional lines, and the raw material logistics also prepared to accommodate this, with connections for two external silos and four Big Bag spaces already in place.
Before even a single part of the entire plant made it to the production list in the Zeppelin production halls though, the entire system was built as a 3D model on computer, using a form of virtual reality. The model was optimized in close collaboration with Hoogvliet production manager Louis van Gelder, his architects and planners, until everyone involved was satisfied. Although this process took time, it proved well worth it even at the planning phase, as it allowed early identification and prevention of conflicts between different parts of the plant, and of bottlenecks that could prove detrimental from a hygiene point of view; maintenance routes could also be secured by virtual means, and each of the buildings received detailed instructions as to which pipes and connections belonged where. Roman Kreher, Project Manager at Zeppelin Systems: “Usually, people transport surplus material to large construction sites of this kind, so that there is no need to interrupt the work. This time, the parts lists were so precise and consistent that we did not once need the truck to return any materials.”