Numerous technical features combine to make wet blasting an effective method of surface finishing.
When expertly combined by an experienced finishing expert such as Rosler, this method can achieve precise and repeatable results on a variety of work pieces from a wide range of industries.
A general understanding of the essential technical elements of a wet blasting machine will help you select a machine for your specific needs as well as prolonging the efficiency and life of existing wet blasting equipment.
The numbered diagram details the wet blast principle and the basic features of a wet blast system.
- Blast chamber with slurry tank – A mix of media and water is stored in this holding tank found at the bottom of the blast chamber. The chamber is made of stainless steel.
- Compressed air – Approximately 70 PSI of compressed air accelerates the slurry.
- Blast gun(s) – One or more guns accelerate the slurry supplied by the slurry pump with compressed air.
- Blast media feed – Media enters the machine.
- Slurry pump – This high-powered mechanism transports the slurry to the blast gun(s). Larger wet blast systems can be equipped with multiple pumps.
- Slurry agitator (stirrer nozzle) – In order to keep the media suspended in the water, the slurry pump diverts some of its flow to a stirrer nozzle placed in the tank to agitate the mix of water and abrasives.
- Overflow – Small media particles, dirt, and other contaminants tend to stay suspended and are skimmed off and sent to the filtration unit.
- Water filtration system – Media particles and debris skimmed off the water’s surface must be passed through a filtration system to separate still usable media and process water from waste. Common filtration methods include hydro cyclones, weir tanks, bag filters, paper band filters, and semi- and fully automatic centrifuges.
- Filtered water – Once processed by a water filtration system, water is returned to the slurry tank and reused.
- Exhaust vent – The water mist mixed with media fines and other small particulates is removed from blast cabinet by suction fan-equipped filters.
Controlling Slurry Concentrations
Depending on the specific wet blast process, the typical concentration of abrasive media in the slurry ranges from 10 to 40% by volume. Establishing the ideal concentration usually requires more or less extensive processing trials.
During the blast process the media wears by becoming smaller or fracturing and must be removed from the system. To make up for this loss, good media must be added. To consistently achieve the desired high-quality blasting results, the established slurry concentration must be maintained within a very tight tolerance range of 1-2%.
This can be done by visual inspection of the viewing glass and manually adding media as needed.
However, in larger blast systems the slurry concentration is controlled automatically with an ultrasonic level sensor, a weighing system, or continuous density measurement.
Adding media to the desired concentration level can be done manually or through an automated, PLC controlled media adder.
The Rosler Way
Building standard and custom wet blasting equipment to deliver precise, repeatable results is the Rosler Way. Contact us to learn how we can solve your surface finishing challenges and to request a FREE sample processing in one of our global CEC.
Upcoming posts in the Wet Blasting Technology Series will include:
- Part 4 – “Typical Wet Blasting Applications.”
- Part 5 – “PureFinish® Offers Food-Grade Excellence.”