Industrial Shock Absorbers Protect Metal Sorting Plant from Damage
If metal drops on steel, even massive dropping funnels can be destroyed, because the impact on the overall design of a dross sorting plant was greater than previously assumed. Simple machine elements solved the problem quickly.
Copper is one of the oldest metals used by humans and is still indispensable in electrical and pipe installations as well as in the automotive industry. The properties of copper are appreciated everywhere. These include first and foremost good formability, strength, resistance, and excellent thermal and electrical conductivity. Established almost 200 years ago as an art and bell foundry, Ulm-based Wieland-Werke AG has evolved into a globally recognized supplier of more than 100 copper and copper alloy materials. Both conventional and novel copper alloys are produced in its own foundry and contain copper as well as zinc, tin, nickel and other materials. The melting of metals produces atmospheric and technological "dross" — a mass containing solid impurities that forms on the surface of molten metal. It is not a pure waste material, but can be recycled.
Wieland-Werke pays particular attention to the development of materials that enable the efficient use of resources and contribute to the protection of the environment and public health. This is made possible above all by close cooperation with customers, institutes, research institutes, and other renowned partners, such as ACE Stoßdämpfer GmbH in the application described below.
Effective Sorting of 4,000 kg Metal Mass
The optimization of a dross sorting plant is, on the one hand, a good example of the economic partnership between two companies that are leaders in their respective fields. On the other hand, a dross sorting plant is also an important component in the environmentally friendly handling of resources. "It separates the metal dross mixture and thus ensures that as much metal as possible can be further processed," explains Felix Scherb, Project Engineer at the company headquarters in Ulm. "If the plant then has to be maintained and repaired at irregular intervals, this thwarts our efforts to work effectively and sustainably". But this was exactly what happened in the first few months after commissioning.
The reason for this was quickly identified. After the metal content was separated into different grain sizes by sieve channels, the metal runners with a mass of up to 4,000 kg were discharged into a hopper. From there, they were transported in free fall and with a loud bang to the end of a 2.3 m long path in a massive steel collecting construction that resembles an oversized drawer. At the above mentioned drop height alone, the pure metal mass, which even in the smallest case weighed as much as 500 kg, caused an excessive load on both the drawer and the part of the overall structure below. The massive structure of the discharge hopper was regularly destroyed during operation. According to Felix Scherb, two factors were decisive for a quick solution: "First of all, our company always gives us a lot of leeway when it comes to making decisions and secondly, we have been working for many years with ACE Stoßdämpfer GmbH, which has often helped us with proven absorption solutions.“
Soft Bed for Giant Drawer
When Felix Scherb got in touch with Udo Fischer, ACE's technical consultant in the Southwest region, he had two possible solutions in mind for the protection of the drawer and the overall construction: The SLAB series of shock-absorbing panels or, alternatively, tube structure dampers. After taking into account the most important characteristics, including weight, drop height and, above all, the cycle of eight impacts per hour, the result was the large-scale use of TC137-90 tubes. Altogether 20 of these safety dampers were installed. On top of them stands the drawer into which the metal chunks fall from the dropping funnel.
ACE's tube safety products for handling large masses mainly include the TC-S and TC product families. They are both cost-effective solutions offering high force absorption. The maintenance-free, modern machine elements cover energy absorptions from 450 Nm to 17,810 Nm continuously and, thanks to high suspension rates, are used not only in loading, lifting and hydraulic devices, but above all in crane systems. The enormous bandwidth is due to the unique dual concept of the TC-S range. The force absorption of the individual TC types from 1,210 Nm to 14,140 Nm is also perfectly sufficient for many designs, especially since, as in Ulm, thanks to their compact design, they can easily be mounted onto steel profiles in five rows of four. The type TC137-90 used is one of the largest models of the safety dampers equipped with diameters ranging from 64 mm to 176 mm.
With a stroke of just 90 mm, only one of these models is capable of absorbing 6350 Nm of force with standard dampers, and even 8,890 Nm in extreme cases. Since their installation in the dross sorting plant of Wieland-Werke AG, the 20 in-line mounted tubes have absorbed the forces evenly and reliably. According to Felix Scherb, maintenance intervals can now be much longer, and there has never been a failure.
This article was first published by konstruktionspraxis.
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