Landy-Novice Posted January 12, 2014 Share Posted January 12, 2014 hello all. we got a shot blasting business and we have a problem. the price of grit is quite expensive and we need to keep prices down for customers and the main factor is of course the grit! we need a way to collect, filter and return to the pot. we want to use reusable grit which is £1000 per tonne but for it to be viable, its needs to be filtered! they use to use a huge hover which separates the dust from the grip into 2 bags, and just drop the grit back into the pot. i've been look for such a thing but had no luck. seen many industrial hoovers but i think hovering up around 200KG of grit/dust per hour will very soon kill it? also found dust deputy. looks interesting but again. hovering large quantities of abrasive will i reckon just kill, and indeed, dust extraction to remove most of the floating dust will really help. ATM we have one of these. which only has one 4" duct in a corner which is near useless! so were planning to add a length of soil pipe (3meters?) down the center of the booth with lots of holes to aid extraction which will hopefully improve visibility? is there a more efficient way to achieve max potential on our extractor? next thing is abrasive recovery plants like this one and a low quality animation to demonstrate it here which are fully automatic and look the dogs whatsits but with a price tag of over 7K its a no go. we are currently reusing the grit which is horrendous! its so dusty you cant see anything and it becomes less abrasive so it takes longer costing time/diesel and electric. use fresh grit is just delightful! cleans surfaces and you can see! does anyone have any suggestions/experiences on recycling grit? thanks in advance. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted January 13, 2014 Share Posted January 13, 2014 I don't have any experience of commercial operation, nor (obviously) of that device you currently have, with "one 4" duct in a corner which is near useless". You add "planning to add a length of soil pipe (3metres?) down the centre of the booth with lots of holes to aid extraction which will hopefully improve visibility?". DOWN is the significant word here, it suggests (to me) that the existing extraction duct is at the top of your working bay. You then say "is there a more efficient way to achieve max potential on our extractor?", and that is the question I'm answering. From building, developing and using my own small cabinet I'll say that trying to extract the dust from the top of the work area is a bad idea. It is best if you can devise some sort of raised floor, through which the used grit, dust, and debris will fall. Extend your extraction duct down to below this gridded floor. If you cannot arrange a raised floor, at least have the suction ducts at floor level. The extract fan will thus draw all the dust downwards, away from your eye level. Secondly, you need to ensure a HIGH volume of air flowing through the work area. Don't skimp on the size of the air intake, and don't filter it. Use baffles if you have to provide some obstruction to grit and debris being deflected out. Ideally, create an 'airwash' system, with the inlet just above your viewing screen, and with a long duct leading to the inlet, so the incoming air builds up some direction and momentum, flowing or washing over your viewing plate. (This assumes you are standing outside the blasting area). If you are standing inside the blasting area (wearing suitable air fed PPE) you still want to follow the basic principle of clean air coming in at the top, dirty air leaving at the bottom. Commercially, you probably HAVE to have some sort of filtration system on the dust extractor. These MUST be kept as clean as possible. I appreciate it's a cost to change them daily, but blocked filters work against the need to keep a high throughput of air. Consider a water trap filter, as this only needs cleaning out, it won't need expensive filters replacing. Alternatively, look at centrifugal filters, like the biggest Dyson in the world, where the air spins round, such that the dust is centrifuged outwards (and down through gravity) while the air travels upwards. HTH. Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 14, 2014 Share Posted January 14, 2014 What you want to look for is a cyclone seperator.... there are calculations and calculators on the web that show you how to fabricate one. Think Dyson, only bigger. I'll explain tomorrow if you're interested Quote Link to comment Share on other sites More sharing options...
redneck Posted January 14, 2014 Share Posted January 14, 2014 Have a look at the HSE website http://www.hse.gov.uk/lev/ You can download it for free, there is loads of useful info on there regarding designs of LEV and how they work. and as robertspark said cyclone filters are pretty easy to build yourself, loads of info on the web. Or just buy a dry ice blaster:) Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted January 15, 2014 Author Share Posted January 15, 2014 I'll explain tomorrow if you're interested please do!! the more info, the more options! Quote Link to comment Share on other sites More sharing options...
robertspark Posted January 15, 2014 Share Posted January 15, 2014 The theory (quick read material) is here: http://www.fkinc.com/pdf/Understanding_Cyclone_Dust_Collectors.pdf http://www.nortonsandblasting.com/nsbhowto-blastroom.html http://www.niro.com/niro/cmsdoc.nsf/webdoc/ndkw5y7gu9 http://lumberjocks.com/SimonSKL/blog/10097 A Calculation Spreadsheet here: https://noppa.aalto.fi/noppa/kurssi/puu-0.4400/luennot/Puu-0_4400_cyclone_calculation_sheet.xls General Design Info http://www.media.rmutt.ac.th/media/e-Book/Engineer/Environmental/AIR%20POLLUTION%20CONTROL%20TECHNOLOGY%20HANDBOOK/9588_PDF_C21.pdf The best site.... down the bottom of the page, it will do a calc for you and provide you with a cut pattern to fabricate one from plate: http://billpentz.com/woodworking/cyclone/cyclone_plan.cfm Sorry, I just work in the hobby class of sandblasting, I did a post a year ago on my setup here: http://forums.lr4x4.com/index.php?showtopic=76893&hl=sandblasting#entry658343 My suggestion would be to do a two stage cyclone filter arrangement, one for the heavy particulate matter, and a second stage for the fine dust before discharge of the vacuum to atmosphere... If it were me, and I was looking to build one, I would look at getting a load of 2nd hand dyson vacuum cleaner motors (maybe 5 or 6 for the amount of grit you're hoping to filter), and place them in a circle ontop of something like an old oil drum... Build your second stage cyclone filter within the confines of the oil drum (on wheels, with a frame to tip it up and empty it out.... if you get the balance point right it will tip with very little force --- something like the cocopan image link below if that helps you to visualise the empty / self balance arrangement) http://images.bidorbuy.co.za/user_images/112/2168112/2168112_130412200848_12April2013_151.jpg First stage I would look to build on another oil drum or something similar. Remember you will get more usable grit back than dust (hopefully)... so you will be emptying the 1st stage more often than the second stage. The dyson motors are great because they are high suction.... but relatively low flow .... I use a dyson to filter my 50kg hobby pot of Garnet, and it takes me about 30mins to syphon it all up, separate the dust from the good grit and get it back in the pot... just in time for a second 45min run as the compressors have cooled down. The reason why I suggest around 5 or 6 is because the pressure would remain constant, but your flow rate will increase by roughly 5-6 times..... note that the pressure loss thought the cyclones should actually not be that high because what you're trying to do is slow the air down upon entering the cyclones so the particulate matter drops out. Quote Link to comment Share on other sites More sharing options...
De Ranged Posted January 15, 2014 Share Posted January 15, 2014 If your willing to do a bit of engineering Years ago my old man played around with systems to clean grain, you get a better price for a cleaner product He used two systems one to take out the dust and one to take out the larger odd ball bits that seem to get picked up, the dust extractor used gravity to seperate the dust We used to run it up the elevator and down into a shute, this is so it builds up a constant speed, then spread it out into a fan so you end up with a wide thin flow you now need an adjustable ramp, then an open area... so you are basicly pouring the blasting media in a wide thin fan, the adjustable ramp will allow you to adjust the curve of the flow you then setup a collection funnel in our case about a meter and a half away The dust being lighter has less mass as it comes off the ramp so can't fly as far.... you will get abit of dust being carried through by the flow of the grit but with a low pressure airline blowing down you can over come a good portion of this You can also separate the bigger bits by putting a lid over the top of the collection funnel, the bigger bits have more mass so fly higher than the lighter grit This will take some experimentation to get right, and different grits will fly different distances so you'd need adjust ability but is a very simple system The second sepperator was just a mess angled about 45degrees ontop of a hooper and pour the grit in from the high end..... I imagine you already have something like this Quote Link to comment Share on other sites More sharing options...
ashtrans Posted January 16, 2014 Share Posted January 16, 2014 Hi, what media are you using ? we found the long lasting hard ones such as iron oxide, cleaned great, laster forever but totally ate the machine, wore big holes everywhere in no time, the cyclone, hoses, nozzles, all of it, Dave Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted January 17, 2014 Author Share Posted January 17, 2014 cheers for your input guys, much appriciated! keep it coming Hi, what media are you using ? we found the long lasting hard ones such as iron oxide, cleaned great, laster forever but totally ate the machine, wore big holes everywhere in no time, the cyclone, hoses, nozzles, all of it, Dave hi Dave, we are using grass grit ATM but we want to venture out and use other types when the opertunity comes along like the sponge stuff and the ali oxide. we're using a 3/4inch nozzle atm. you mention that iron oxide cleans well. got any info/pics on the eqipment used? thanks. Quote Link to comment Share on other sites More sharing options...
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