Dust collectors are an oft-overlooked component of any blasting and extraction system, but their role in dust removal is critical.
Having built and operated abrasive blasting equipment for over 40 years, Protoblast has amassed a wealth of experience and information about dust collection.
Below, Protoblast will share 6 major points that, if correctly implemented, will produce the best returns for your business (and mistakes to avoid that they continue to see made in the industry):
- Safety with the most effective velocity
- Reduce blockage with correct pressure
- Fan design is critical
- Filter ratio to maximise lifespan
- Reduce maintenance with higher filter area
- Lower energy costs with variable speed drive
1. Volume + velocity = visibility + safety.
With blast chamber ventilation, there is regulation that stipulates the minimum velocity required within the chamber. This is calculated by locating the smallest cross section, and calculating the volume needed to move air through that section at the required velocity.
Maintaining this velocity is the most efficient way to keep the chamber free from dust and therefore provide adequate visibility and a safe environment for the operator.
2. Correct Pressure = minimum blockage.
This is especially important when the dust collector is positioned at a distance from the blast chamber. The pressure is the energy in the moving air and keeps the dust from losing velocity. If pressure is lost, dust in the ducting can drop out, causing blockages.
The other aspect to take into consideration is the friction of the air through the filters, which requires more pressure from the system in order for the dust to pass through. The higher the dust loading on a filter, the more pressure is needed to ensure flow.
3. Fan design= maximum efficiency = longevity.
Protoblast uses the Backward Inclined Centrifugal system as the most efficient design across their product range. This design eliminates overloading, and when using a direct mount there are no extra bearings to worry about and no power loss through belt drives.
4. Filter quality = long life.
The filters really are the heart and soul of the dust extractor, as this is where the cleaning is done. If done incorrectly, bad filtration can lead to a whole host of run-on problems. Sand blasting dust is very fine and very abrasive, so trying to save money by lowering the grade of filters is counterproductive. Protoblast have used the Cellulex filter cartridge for decades; these cartridges have a filtration efficiency of 99.99% of all particles above 1.0µm. This means that the air being exhausted from the dust collector meets all EPA requirements, provides a cleaner working environment and increases productivity.
5. Higher filter area = lower velocity = less maintenance.
This is very important, and many cheap dust collectors will fail because of this. The more filters there are, the more area there is for the air to pass through so the velocity is much lower. The lower the velocity the longer the filter lasts and the less pressure the fan will have to produce. Protoblast recommends on an air to cloth ratio of 2.212:1.
6. Variable speed drive = lower energy costs.
What’s your available power? Large volumes of air mean very large fans and large fans need large motors. For example, a blast chamber with a cross section of 5m x 5m requires 21,000cfm of dust collection.
This would use a 22kW motor which has a full load current draw of 38Amps, but the big issue is on start up as the motor has the inertia of the fan impellor to overcome so effectively it is starting under load. With standard direct online starting the motor needs 7-8 times the full load current, so in this example it would be 266amps. This is a massive requirement, and by law the wiring and circuitry has to be sized accordingly.
The solution for this is a variable speed drive (VSD). The VSD Protoblast uses is a fully adjustable unit and best of all it will only draw a maximum of 10% more than full load current on start up. Not only on start-up will you save power but the fans can be slowed down during operation and when running at 75% of full speed the power consumption is halved. This mean a massive saving on your power this is why Protoblast equipment continues to save you money every day.