A sandblasting blower ( blast an abrasive (sometimes sand, but today mostly other materials such as blast furnace slag, glass granulate , corundum , steel , plastic granulate , nutshells, soda , ice crystals, CO 2 -Snow pellets) is blown onto objects to remove rust , paint , burrs or the like or to roughen them. The use of the device is also called sandblasting .) is a technical device that uses compressed air or a centrifugal wheel to
A typical system for "sandblasting" (see photo, technical term "compressed air blasting with solid abrasive") consists of a pressure vessel filled with abrasive, which is connected to a compressed air hose "on the side". When the fan is activated, an elastomer cone closes the filling opening. The blasting agent is dosed into the air stream and transported to the nozzle through the blasting hose. Conical Venturi nozzles are common today , which accelerate the abrasive to a higher speed than a cylindrical nozzle by utilizing the Venturi effect. The activation / deactivation is carried out by an electrical control device, which is operated by a dead man's switch in order to avoid (potentially fatal) injuries if you lose control. Air pressure dead man switches (hose squeezers) that used to be common are no longer in use today because of the delayed reaction.
There are blasting guns that allow operation with one grip and a "trigger", but in large-scale use, hose nozzles inserted directly into the blasting hose are much more advanced due to the greater flexibility and area performance (efficient area coverage through fast and energy-saving swinging / trembling of the flexible hose) spread.
Smaller injector blasting devices suck the abrasive from a container (see Bernoulli effect ) into the air flow. These devices are easy and flexible to use, but have a significantly lower performance than pressure boiler systems.
A special form is moist blasting, in which small amounts of water are released into the air stream at the nozzle in order to reduce the development of dust. However, this may be the case on steel surfaces to be coated. U. problematic, as the surfaces build up very quickly rust film and can therefore only be worked with special coating materials.
Since many blasting media are hygroscopic, i.e. they absorb moisture and humidity, dry air is required for sandblasting blowers and sandblasting kettles. The compressed air provided by a compressor can only be used for sandblasting if it has been cooled and dried beforehand.
Blasting with quartz sand is prohibited in Germany by the professional association for commercial enterprises, as fine quartz dust leads to silicosis (also known as dust lung). For this reason, various non-silicon blasting media , in the simplest case melting chamber slag, are used as alternatives today.
The colloquial so-called “ slurry blasting ”, more correctly “water washing with solid blasting media”, uses a blasting agent to achieve an abrasive effect when washing water with different pressures (colloquial “Kärcher”). This procedure is not part of compressed air blasting and is not the subject of this article.
Sandblasters are also used in art for processing objects; there called sandblasting technology . This also includes sandblasting glass, where clear glass, e.g. B. with interior doors, the whole or part of the surface can be matted.
Dry ice blasting
An alternative method is dry ice blasting . Here dry ice is used as a blasting agent.
The sandblasting blower was invented in 1870 by the American Benjamin C. Tilghman and is based on the jet pump . Tilghman was an officer in the Civil War and passed a homestead where all the windows on one side of the house were matt instead of transparent. When he asked how this had happened, he was told that very often a sharp wind blows from a hill on the homestead, which takes a lot of fine quartz sand with it. This gave him the idea of the sandblasting blower, which he implemented industrially after the war. The first applications were matt figures that were applied to a shiny base.
With slurry blasting, the abrasive is enriched with water until it is saturated. In contrast to blasting blowers for dry blasting media, slurry blasting with damp or soaked blasting media creates a far lower dust load for the blasting staff as well as for the environment. Another advantage over dry blasting is that the abrasive can be reused. The first patent for a blasting system based on this process was registered in 1994 by Hubert Busch from Langenfeld in the Rhineland and granted by the German Patent Office.
In the same year, the low-pressure process was developed by Karl Schmidt. This process is suitable for the gentle restoration of surfaces of various types with all commercially available granulates - especially for the construction industry as well as for stonecutters and restorers . The gentle cleaning with low blasting pressure, when the grains hit in a controlled and targeted manner at a 45 to 90 ° angle, results in an even blasting pattern.
- Carus Sterne : How dwarves do huge jobs . In: The Gazebo . Issue 43, 1873, pp. 700–702 ( full text [ Wikisource ]).
- The Tilgman sandblower . In: Innsbrucker Nachrichten , November 25, 1875
- ↑ US Patent No. 108408 - "Improvement in cutting and engraving stone, metal, glass, & c." teh-stroy.ru