Coping with the challenging task of core sand removal
For the removal of sand cores from various grey iron pump components the Bobruisk Machine Building Plant purchased a spinner hanger shot blast machine, type RHBE 27/32-F, from Rösler. The customer specifications called for a special design that can cope with the harsh foundry conditions and offers reduced equipment wear and high uptimes for a highly cost efficient shot blast operation.
The removal of sand cores from steel castings poses special challenges to many shot blast machines. Abrasive core sand increases wear of components such as the blast chamber and blast turbines resulting in higher operating costs and lower uptimes.
Therefore, it is not surprising that wear rate and uptime were key factors, when the customer decided to purchase a new shot blast machine as part of a foundry modernization project. Bobruisk Machine Building, located in Belarus, is the largest manufacturer of special pumps for oil refineries, the petrochemical industries, the steel and mining industries and many other sectors in the former GUS countries. The pump components consist of grey iron and steel castings and require an intensive internal and external blast cleaning step after having been cast.
Convincing adaptation to the harsh foundry operating conditions
For the required shot blast machine Bobruisk had issued a tender invitation to which eight equipment suppliers responded. In the end the customer decided to purchase the spinner hanger shot blast machine RHBE 27/32-F from Rösler. A key factor was the cost efficiency of this shot blast system designed as special foundry version with optimized wear protection of critical equipment components. This included the fabrication of the blast chamber from 10 mm (0.4”) manganese steel with additional manganese steel wear liners on the blast chamber sidewalls. The blast zone itself is protected against wear with 25 mm (1”) thick hard metal plates. The wear liners require no special fastening elements allowing easy and quick installation. In addition, all liners overlap leaving no gaps so that the blast chamber is optimally protected against wear.
The foundry version of this shot blast machine can be equipped with different blast turbines. The Bobruisk spinner hanger machine is equipped with four turbines, type hurricane H 42, each with an installed power of 22 kW. The same shot blaster can also be equipped with Rösler Long Life high performance turbines of the Gamma series. These are made from hard metal and offer up to 16 times longer lifetime. The pump components are either processed as large, single pieces or in batches of multiple, smaller pieces with batch weights of maximum 5 metric tons. Adjustable shell valves allow adjustment of the media flow taking into account the component size and shape. A special blast program for core and moulding sand removal allows sequentially activation of the turbines. This allows the sand to be removed in smaller quantities and thus prevents a sudden surge of sand that could overwhelm the blast media cleaning/classification system.
Blast media classification with a cleaning efficiency of up to 99.7%
Another technical highlight of the RHBE 27/32-F is the blast media cleaning system designed for sand contents in the media of up to 20%. Coarse particles are removed from the media/sand mix with a vibratory screening system before it is guided to a dual drum magnetic separation system. A clever guide system ensures that the media/sand mix is evenly distributed over the complete drum width thus producing a very thin media/sand curtain. The strong electro magnets placed inside of the drums guarantee a separation efficiency of up to 99.7%. The low residual sand content in the blast media helps to significantly reduce the overall wear rate.
The dust collector is equipped with filter cartridges that are specially designed for a relatively heavy sand load and offer a longer uptime. The residual dust is < 1 mg per m3 of cleaned air.