Vacuum-soldered mixing elements

Manufacturing
The manufacturing process of static mixers with gapless soldered mixing elements has been tested and developed over a period of several years. It starts by producing a special tube for the corresponding inner diameter. The mixing elements to be soldered are furnished with a longitudinal slot on the side where the solder is subsequently introduced. After this, the mixing element chain is inserted into the tube which is subsequently warmed up in the vacuum oven in specified temperature levels to over 1000°C. This is the melting phase. The solder is diffused during this process into the tube material and into the elements – a crystal transition takes place. In the crystallisation and maturing phase the gapless connection between mixing element and tube interior is created.

Applications
Each year, several hundred pieces of these gapless mixing tubes are integrated for instance into tube bundle heat exchangers in order to significantly improve the heat transfer and avoid caking. Other applications can be found for instance where dead spaces have to be avoided. This is a frequent demand in the pharmaceutical industry. For processes which generate large axial forces due to the product characteristics (very high viscosity), soldered mixing elements are also frequently used as this enables the forces to be fully delivered to the tube.

Gap clearance
By using measurement technology (e.g. X-ray, ultrasound) it is not yet possible to prove gap clearance. During specified test procedures the elements case confusing shadows, thus no definitive statement is possible. Up until now, only a visual assessment of the components has been possible.