Re: Dust Problem
You may look into installing a large size hood close to and just above this machine. Design this hood to capture the air-borne dust. Capture velocity depends upon dust particle size but it should not be less than 300 ft/min. Use Stoke's Law to calculate this velocity. Provide a centrifugal vacuum blower for this air flow and use a dust collector in the line to the blower.
This should solve your problem.
Regards,
A. T. Agarwal
Consulting Engineer
polypcc@aol.com ■
Dust Problem
The process needs to be enclosed as much as possible. Use hinged transparent polycarbonate panels. (These can take the place of the safety guards on the machine). Allow minimum openings for exhaust air to enter. Calculate the exhaust quantity by: open area x intake velocity (minimum 1.5 m/s). You should end up with modest exhaust flow.
Refer to "Industrial Ventilation" by ACGIH for the whole design procedure if needed. Figures VS-45-02 and -05 show similar operations.
Michael Reid. ■
Polypropylene Dust Is Explosive
You need to collect the dust as it forms over the machine using a hood as already suggested. The dust should go to a dust collector that is fitted with proper explosion protection such as venting, a Q-Rohr, or suppression. I can help you with explosion protection options and sizing.
Regards,
Bill ■
Dust Collection
All fine dust presents potential health hazards that should not be ignored. For a discussion on wood dust that is not far removed from the plastic dust you are dealing with, please see http://BillPentz.com/Woodworking/Cyclone/Index.cfm
In terms of your collection it is not ample to just calculate the airflow required to move a particular particle size. You also have to increase the airflow amply to overcome any air movement caused by belts, motor fans, cutters, etc. that tend to launch the fine dust. With most smaller woodworking tools this tends to be on the order of 800 CFM. At typical dust collection pressures air is more like water in terms of not being very compressible. Almost any reduction in duct diameter or even sharp turn will significantly increase resistance and greatly reduce airflow. Testing shows we need 6" ducting driven by at least an 11" material movement impeller turned by a 3450 RPM 1.5 hp motor as a minimum to exhaust directly outside with minimal ducting and no filters. Adding filters and a cyclone separator requires a 14" material handling impeller turned by a 3450 RPM 3 hp motor. An electronic spreadsheet that provides a scalable design to build a cyclone separator is on these same pages.
Bill Pentz ■
Re: Dust Problem
In viewing the Marchesini Blister machine, this machine has all the operating components up high, above the cut material and open area below, from what I can tell. Additionally, the dust probably has static cling issues, so adding plastic hoods and covers for containment would be a problem.
I would suggest slotting the plate the material sits on under the cutters, then applying proper collection there to suck the particles down. There are other design issues with the collector and collection flows, but nothing an experienced collection company like us could not handle.
We do dust collection for coal conveying normally, but this would be an interesting application to handle. ■
Re: Dust Problem
Another option (depending on your conveyor configuration) is to use a short vibratory conveyor section or gravity chute with perforated holes to act as a screener and down draft table pulling the fines away from the finish product. In this arrangement no hoods would be needed that block the view of operational personnel. ■
Dust Collection
Dust collection would appear to be the most straight forward solution until you look at the details.
1 - How will the high pickup air velocities affect your process?
2 - What is the best pickup hood configuration that maximizes pickup, yet minimizes amount of conditioned air removed
3 - With a combustible material a conventional collector needs to be designed with blow-out panels designed for Kst valve of material. This collector should be mounted outside and therefore must be insulated to prevent condensation/freezing during cold weather.
4 - If you are removing large amounts of conditioned air you now need to assess your HVAC requirements and possibly increase the size of this unit
5 - How much energy consumption will this approach consume both from the collector and make-up ventilation?
All of the above is technically feasible. Before going down this path I recommend you re-evaluate your process to see if you can re-configure process to minimize generation of material. This may be a more cost affective approach. If this is not feasible then evaluate the full requirements of a conventional pulse-jet system, cyclone collector, or even a small wet scrubber system.
Chris Blazek, Illinois
blazekc@benetechusa.com ■
Separation Technology
Typically, we use a special design of an air wash system, but this could also be incombination with a blowing system. As a push-pull type system. It is easier to blow a particle out of the boundary layer than it is with suction. As long as the particle is not buried under other material, it can be pulled away or separated from the other product. Each particle and product will have design characteristics that enable it to be separated in som form or another. Prosolids method of a vibratory table will work as well, but with moving parts. We tend to use air on most of our separation projects, sometimes water cyclones in conjuntion with the project type. Does the product move past on a belt or can it pass under a type of hood design for separation?
We have for instance designed systems to remove leaf fragments off the tops of flower pots as they are going down a conveyor for packaging or fine paper particles and fragments from glass bed in a fluidized bed dryer. These types of projects seem similiar to yours, but probably not exactly.
The ACGIH is typically a starting point, but in no way the be all end all answer for your particular needs. A dust collector companies knowledge stops here, some rarely use it, whereas someone who knows about pneumatic conveying and dust collection, but more importantly tests for quantified analysis, will be your best answer.
The trick, as we have learned, is that each application is different and therefore needs to be tested, and analyzed.
We do this procedure at our facilties, to gather all the neccessary data, then we design a system that works.
Customers are always happy, and are not used as guinea pigs by equipment companies suggesting only dust collection and taking away half of your product as well.
give me a call at 1-905-563-8500 and we can discuss the application. We can solve it for you, because that is what we do.
Sincerely,
Donald Roy ■
Re: Dust Problem
Originally posted by ssarkar007
We are using a Marchesini machine for packaging of contact lenses in their polypropylene blister containers. The machine uses a die cutter for separating an array of 6 into single blisters. This operation generates polypropylene dust which accumulates on the machine, distributed throughout by the conveyors. The current practice is to periodically blow off the accumulated dust using a compressed air hose manually. This is certainly not the most effective method as the dust is rendered airborne, some of it settling back on the machine. The greater concern however is that the airborne dust is also a nuisance for the operator from an inhalation hazard and skin irritation perspective.
Need help in addressing this issue.
Try to use a Pelletron DeDuster to remove dust. This might be the easiest way to solve your problem. See also web page www.pelletroncorp.com for more information on DeDusters. ■
Dust Problem
We are using a Marchesini machine for packaging of contact lenses in their polypropylene blister containers. The machine uses a die cutter for separating an array of 6 into single blisters. This operation generates polypropylene dust which accumulates on the machine, distributed throughout by the conveyors. The current practice is to periodically blow off the accumulated dust using a compressed air hose manually. This is certainly not the most effective method as the dust is rendered airborne, some of it settling back on the machine. The greater concern however is that the airborne dust is also a nuisance for the operator from an inhalation hazard and skin irritation perspective.
Need help in addressing this issue. ■