Raw material cycle: from chip to briquette to product - Case Study

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Courtesy of Ruf Maschinenbau GmbH & Co. KG

Thanks to their briquetting system from RUF Frischhut can redeploy production scrap and melt it again

Ludwig Frischhut GmbH and Co. KG have closed the circle on their raw material cycle by utilising a briquetting press from RUF: cast chips produced during the machining of parts for water supply and sewage disposal are pressed to solid briquettes and then melted in the in-house foundry and cast to form new raw products. The melting of the loose chips would however not be possible. Therefore the company is saving money as the sales price for loose chips is markedly under the purchase price for raw materials for the foundry.

Ludwig Frischhut GmbH and Co. KG, based in the lower Bavarian town of Pfarrkirchen, produce water supply and sewage disposal products for sale all over the world in the form of high performance cast parts for pipeline networks. The quality of these products has even convinced customers in Australia to accept the longer delivery times inherent. The parts such as belling components and flanges or shut-off devices have to survive years or even decades of service life when they have been installed or are utilised in underground pipeline networks. Customers who are located closer can rely on Frischhut to deliver within a few days when the case arises that extra or even different parts are required on-site suddenly. The company from the area around Rottal-Inn operates two well networked sites: machining in the headquarters in Pfarrkirchen and the foundry situated around 40km away in Neumarkt-St. Veit.

The longevity of the products owes a lot to the know-how present in the company regarding coating with epoxy resin powder using the whirl sintering method. However corrosion prevention is addressed even earlier by Frischhut: The cast parts – almost exclusively spheroidal graphite iron, i.e. ductile cast iron – are machined dry; so no cooling lubrication is used while milling, turning or drilling.

Loose chips cannot be melted

The briquetting system from RUF has allowed Frischhut to solve a long term problem. The chips are basically valuable raw materials or they would be if you could melt them. Plant manager Christian Greil explains: “Because the surface of the chips is very large relative to their weight, they would either deflagrate or would be pushed against the outer wall above the melting area of the furnace as a result of the thermic properties. They would just never reach the melting area.” For decades Frischhut sold on the chips they were producing, at a low price. They were collected in a container and picked up by a scrap dealer.

This did not make economic sense. Because chips are not easily melt-able, they are worth a lot less than the raw iron material which was purchased for the foundry. Even though the prices fluctuate constantly it can be said that on average, according to market research carried out by RUF, the price difference was around 100 Euro per ton. And the price achievable for chips is also negatively influenced by the relatively large surface area which means more corrosion when compared to large pieces of scrap.

When it comes to highly valuable ductile cast iron another benefit arises: Frischhut receives back exactly the same material which was produced with much effort previously, including the expensive alloying element. Therefore the problems of scrap purchased externally which may not meet the high quality demands, are avoided.

Press tests and good advice were the convincing factors

All of the disadvantages are negated by briquetting. The compact briquettes are easier to store and transport – and can be melted without a problem. In addition the quality of the metal is raised because when the chip is pressed to a briquette shortly after it has been created then corrosion gets almost no time to attack the chip.

When Frischhut became aware of the possibility of briquetting they were quickly in contact with RUF on account of the company’s great reputation and of course, its proximity. “We had had no experience with this kind of technology. Therefore it was very important for us to have experts nearby” says Greil. And the competent advice was the convincing factor to choose RUF. In order to be sure that briquetting Frischhut’s chips was a viable option and to determine the ideal briquette size, the company had RUF do some test pressings with their chips in RUFs technical center.

Together with RUF, Frischhut were able to proceed step by step. After the successful test briquetting, Frischhut started to press their own cast chips with a rented press in 2004. The briquetting system RB 4/2800/60S has a 4kW motor which enables the chips to be pressed with a specific pressing pressure of 2,800 kg/cm². The cylindrical briquettes have a diameter of 60mm. RUF’s fitters adjusted the press on site exactly according to Frischhut’s requirements. They equipped it with a larger hopper with special geometry.

Fully automatic and reliable for 10 years

In the meantime Frischhut has taken over the press “and we are very satisfied with it” emphasises the plant manager. The system has been running fully automatically and reliably for ten years now. The chips are extracted from 12 machining centers in the production area and are transported via pipelines to the collecting hopper of the press. The press is located in an enclosure built on to the factory. When the pre-determined filling level has been reached sensors ensure that the press starts automatically. As soon as the hopper is mostly empty, the press automatically stops.

There are only two manual tasks to be carried out on the press: The collection container with the briquettes must be exchanged for an empty one and the storage container for the dosing of the minimal amount of oil necessary, has to be refilled. The aforementioned is a RUF developed system which is necessary at Frischhut because briquettes pressed from completely dry chips break apart relatively easily. “The dosing system enables us to drop on minimal amounts of oil” explains the plant manager. “Just enough to keep the briquette stable. The amounts we are talking about are less than tenths of a percent.”

Briquettes are easy to handle in the foundry

Depending on demand, two or three shifts are worked at Frischhut in the chipping production area. The enlarged hopper means the RUF press meets all the requirements, flexibly. That is important because the press is not supplied with chips continually. The chips are collected in collecting containers in the chipping production area; these can be 1 to 1.5 cubic meters. When a container is mostly full the employee responsible inserts a suction nozzle in the container which sucks out the chips. Therefore the chips come in batches to the press. The system can briquette 120 kg of chips per hour.

In briquette form the company can now directly reuse their own production scrap. The space which was previously required for large containers is now no longer necessary. In fact only the grey cast iron chips which are produced in very limited amounts are collected separately and disposed of. The briquettes have a diameter of 60 mm, a height of about 40 mm and a density of 5.3 kg/l. Each one weighs about 600 grams – “a weight that we can deal with very well in our foundry” says Greil. The employees in the nearby plant in Neumarkt-St. Veit transport the briquettes to the electric furnace. Therefore the briquettes are melted down with minimal melting loss. Extra transport effort is not needed because the truck which brings cast parts from Neumarkt-St. Veit to be machined in Pfarrkirchen simply brings the briquettes on its way back. And so the circle is closed and the profitability is increased.

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