TPT March 2007

The principle of a copper tube purging system is shown in figure 16. The purging station comprises of an atmosphere supply lance and a clamping lance. The purging system is connected to one side of the coils, which means that the oil-laden purge gas is blown out of the coils and into the furnace chamber. The inert gas passes through a lance to a manifold pipe at the tray and then into the tube coil. This inert gas tube purging system is available for all the above-mentioned furnace types. The only condition is indexing product conveyance through the furnace.

Results Otto Junker have equipped many roller hearth furnace lines with this copper tube purging system. Examinations have shown that this reduces the carbon deposits or residual oil inside the copper tube by up to 90 per cent as compared to furnaces without this purging system. This satisfies the exacting demands made on copper tubes for air conditioners.

› Figure 17 : Example of an annealing and packing facility

• Loading into baskets at the coilers • Loading onto the furnace line • Removal from furnace line • Handling in the packing area

These repeated handling operations also increase the risk of damaging the coils – particularly when thin-walled tubes are concerned. With the new concept, only a single loading and unloading operation takes place between the coilers and despatch. This is achieved through the use of recirculating coil supports (trays). Moreover, these steps are robotized, ie all coil handling by human operators is eliminated. The return of empty coil trays from the packing line to the coiler is achieved via a forklift truck or roller conveyors. The benefits of this materials handling concept include the following: • Fewer handling operations, meaning a reduced risk of damaging coils • Full integration into existing plant configurations is possible • Capability for full integration of the Otto Junker furnace • Automation can be introduced in several stages • Payback period of about 2 years for each loading/unloading station 4. Conclusion Based on the complete process route beginning from the metal melting to the final annealing of the high quality copper tube, some very innovative technologies for the thermal processes are available. Despite the fact that the overview could not touch all areas in detail, it should inspire technological discussion among the specialists. A schematic view of this system is given in figure 17.

Inert gas tube purging system with connection to both coil ends

In this case the inert gas blown through the coils is discharged from coils and led out of the furnace. The advantage of this system is data logging of the purging operation is possible. Instruments are connected to measure flow and pressure of the purging gas flow to guarantee and record that each coil has been purged with the required amount of inert gas. This system requires some special skills of the operators because the inside of the coil is especially difficult to connect. To date, in Europe this system has not normally been required. Oil trap Evaporation of the drawing oil from the inside and outside tube surfaces increases the oil concentration of the recirculating inert gas atmosphere. This oil condenses in lower temperature regions of the furnace or local to the entry vestibule and cooling zone where oil drops may form. These drops in turn may reach the product causing unwanted marks. Hence it is necessary to clean the furnace atmosphere. One possibility would be a permanent exchange of inert gas by permanent input and discharge of a certain inert gas flowrate but this is of course very costly. Certainly a better solution is the installation of a filtering system. Otto Junker have designed and improved such a filtering system in recent years.

The Otto Junker concept for automatic handling of pancakes

Otto Junker – Germany Fax : +49 2473 601 600 Email : info@otto-junker.de Website : www.otto-junker-group.com

The workflows involved in the heat-treatment of copper tube pancakes are traditionally labour intensive, requiring multiple loading and unloading steps.

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M arch /A pril 2007