French supplier of Refuse Collection Vehicles places his trust in Röslerâs blast cleaning competence
The French SEMAT SA is a subsidiary of the German Zoeller group of companies and specializes the design, production and servicing of RCV and street washersâ vehicles. SEMAT, founded in 1945, is headquartered in La Rochelle, a town on the Atlantic coast. There, the company recently erected a new manufacturing building filled with state-of-the-art industrial equipment. The central feature is an indexing continuous feed spinner hanger blast machine, model RHBD-T, from Rösler.
In the new building in La Rochelle bodies are welded together from steel sheets and subsequently prepared for coating. The surface preparation consists mainly of the removal of scale from the welding process but also rust. This is a typical blast cleaning operation, one of numerous shot blasting tasks. Because the components to be blast-cleaned are really big, the SEMAT project was particularly challenging. For example, the welded bodies for garbage trucks can be up to 6,500 mm high and 4,000 mm wide. Ronny Paasche, global sales expert at Rösler explains: âInitially we discussed several different options. But we decided very quickly that a continuous feed spinner hanger blast machine represented the best solution. It allows the customer to blast his large components within short cycle times with a high degree of efficiency and a relatively low energy input. And, compared to classical continuous blast machines, vertical processing saved a considerable amount of space.â In this case âverticalâ means that the components are transported into the blast chamber upright for an all-around blast coverage.
But it was not only the compact equipment design that convinced SEMAT to buy the blast machine from Rösler. Ronny Paasche continues: âThe customer was particularly impressed by the numerous technical features, which are part of our standard equipment but are considered as state-of-the-art in the market.â
Gamma 400G turbines offer a maximum of blasting power at relatively low energy consumption
Depending on the preceding manufacturing steps, the rust and scale on the components can be extremely hard, requiring intense âfirepowerâ by the blast media. This is guaranteed by nine Gamma 400G turbines mounted on one wall of the blast chamber of the RHBD-T machine. The work piece, hanging on a special fixture that constantly rotates and oscillates back and forth, is exposed to the blast stream of the nine turbines. This ensures excellent, all-around blast results. And thanks to their innovative, energy-saving design, the Gamma turbines only need a power of 11 kW per unit. But since they accelerate the blast media to a comparatively very high throwing speed, the Gamma turbines produce optimal results. After a cycle time of about 10 â 15 minutes the containers leave the blast machine completely clean with a cleanliness degree of 2,5 SA â ready for transport to the painting line. A manual control system allows calling up about 30 different blast programs so that blasting time and intensity can be adapted to the special processing challenges of each individual container. Therefore, the cleaning results are highly consistent, even though the raw work pieces may not always have the same surface conditions when entering the blast machine.
Optimal media recycling and cleaning guarantees high cost-efficiency and sustainability
A pre-condition for economic and sustainable shot blasting operations is a highly efficient blast media recycling and cleaning system. The center of a well-functioning media cleaning system is the cascade air wash separator. Compared to competitive equipment the air wash separator in Rösler blast machines is considerably wider and, thus, guarantees a more thorough cleaning effect for the media. âThe extra wide air wash separator permits a very thin media curtain ensuring that contaminants, such as debris, broken down media, etc., are consistently removed from the blast mediaâ, explains global sales expert Ronny Paasche. âContaminants left over in the media recycling system will damage the throwing blades, the lining of the blast chamber and even the work pieces. Thanks to our extra-wide, highly efficient air wash separator we have, therefore, significantly less wear and tear in the shot blast machine. Particularly scale particles can be extremely abrasive and must, therefore, be completely removed from the media.â An additional benefit of the extra wide air wash separator is the reliable discharge of undersized blast media. Because the excellent cleaning system in the Rösler machine results in a better media classification, it also helps reduce the overall media consumption. Especially helpful in the case of the SEMAT machine was the fact that the air wash separator is located 10 meters above ground. It allowed installation of a flap screen that automatically discharges foreign objects such as screws, flash, etc., from the media recycling system. Emptying the screen is controlled by a timer.
Other technical details in the SEMAT blast machine ensure that the entire blast cleaning operation can be performed safely and effectively. For example, a media return hopper covered by a sturdy grate is built into the floor at the machine exit. This guarantees that the machine operator can remove any residual media from the cleaned work piece without the risk of slipping on blast media lying on the floor. A special auger transfers the collected residual media back to the media recycling system.
Effective dust removal guarantees maximum uptimes
Another extremely important consideration for the economic operation of a shot blast machine is the effective dust removal from the blast chamber. In the SEMAT machine the air stream loaded with dust is initially guided to an expansion chamber, a so-called dropout box, containing an impact plate. There, particles too small for the shot blast process but too big for the dust collector, are discharged. Only very fine particles are transferred to the dust collector. This extends the usable life of the dust collector and the uptime of the filter cartridges.
The air extraction volume is calculated on the basis of computer-based air flow simulations, which have become standard procedure at Rösler. This ensures that after it has been cleaned in the air wash separator, the blast media contains no dust residues whatsoever, ready for the next blast cycle. The work pieces coming out of the blast machine must be completely free of dust so that their surface provides perfect conditions for the subsequent coating operation.
Safe, sturdy and easy to maintain: The SEMAT blast machine fulfills all expectations
In many companies the blast cleaning operation of large weldments is still done manually. But the industry is slowly phasing out large, inefficient blast rooms, where the components are manually cleaned with extremely expensive compressed air. In comparison to these manual operations the advantages of the spinner hanger blast machines are quite obvious: Manual blasting of large components requires processing times that â compared to machine blasting â are multiple times longer. Personnel for this physically demanding job is difficult to find. At the same time, the compressed air usage and, thus, the energy consumption is very high. Automated, mechanical systems offer a much higher capacity, are more economical and produce absolutely consistent results.
Ronny Paasche from Rösler concludes: âRecently we delivered a blast machine similar to the SEMAT system to another customer. With this machine our positive experience from the project at SEMAT was extremely helpful. We are pleased that our innovative approach to challenging shot blasting tasks is helping us to secure new business.â
