well finally landed the blasting job that will enable me to by my own equipment! (8'x12' sign face, hdu)...now here is my problem. what size compresser to use with a pressure pot. the one i'm looking at is a 150Lb presure blaster and operates from 80psi to 125psi. now the 2 compressures im looking at is a 5horse 17cfm @ 175psi and im woundering is this compresser still to small or do i need the 7horse 25cfm @175psi. the cost difference is conciderable. also there is the issue of 2stage and 1stage.
what system do you have?
Posted by Dale Feicke (Member # 767) on :
This isn't an everyday deal for me, Chris, but I'd say the smaller one will work. I have a 5.5 hp 12cfm@150psi, and have done several signs in the 6X8 ft. area. Couple things to keep in mind. With mine, I do need to take a break once in awhile to let the compressor catch up and breathe. It will gradually go down on air. But, you will naturally want to take a break every now and then on this size sign anyway. Most likely, your mask will fog over with foam dust, and you'll need to stop to clean it. Also, the HDU is much softer and easier to blast than redwood, or cedar, so you really don't need as much compressor to do the job. I'm sure you'll get other input....hope this helps...and maybe saves you some money.
Posted by Laura Butler (Member # 1830) on :
We were doing them at home with a single stage, big tank ...don't know how many CFM's but it wasn't enough. We kept having to wait and let it catch up or I was constantly having to fill the pressure pot.
We started renting one of those compressors that are on wheels and two tanks next to each other... 18 cfm's's. We hooked that one with our bigger compressor and did better but it still took hours and hours to blast a 4x8 sign.
Recently I have been exchanging services with a customer that has a 2 stage...don't know how many cfm's, but I never have to wait for the compressor to catch up. I recently did 3 cedar signs, 3 x 5' and got it down to about 1.5 hrs. I probably spent 15 minutes just re-filling the pressure pot.
Also consider that sand blast nozzle. My customer has made up a nozzle using a gas fitting and the ceramic tip, so I don't know how much better it would be with a bigger nozzle.
To me, two stage is the only way to go.
[ January 17, 2005, 03:04 PM: Message edited by: Laura Butler ]
Posted by Chris Lovelady (Member # 2540) on :
i know that there should be an min. of an 80/20 ratio in time usage(80% running 20% resting) so what that means to me is that the compressor should be larger that your max usage. other wise you burn up motors and pumps before there time.that does not mean takeing breaks and letting the compressor catch up...which is what i have been doing with a smaller compressor and a gravity sifon pot. with the size of the aera and the amount of time it would take, im ready to invest.
does any one have a system that you are doing this and what are you using.
thanks for all the imput...it is all good and helps.
chris
Posted by Glen Perye Jr (Member # 159) on :
The only consideration in buying a compressor should be the maxium cfm rating of the tools and or blaster you are going to use. CFM is volume of air moving as cubic feet per minute. If you don't have a compressor rent one and try it. the rate of return on compressors from and to the shut off/ on point will increase if the tool or blast nozzle is straving the compressor will stay on all the time. which will cause overheating. and other problems.Also 2 stage means the pressure is built up an two different cylinders after passing thru a device called an intercooler. have you ever wondered way in most stories about blasting you will see a two wheeled older style construction compressor. it's the VOLUME man not the PRESSURE. if you don't have a blast cabinet large engough to hold the sign. And air system for breathing. see about farming the job out to somebody that does blasting all the time. then go to harbor freight buy a small cabinet and compressor shoot small projects to play with. Most shops that do blast sign work. farm out the blasting till they get a stream of work to get the right equipment. I will not even start about the problems blasting with sand. Silicosis (spi) upset neighbors,calling laywers, your other half if you have one pitching about the dust drifting everywhere. Posted by Chris Lovelady (Member # 2540) on :
the volume of my work is increasing and the local blaster has never done very good work for me. he blasts water tanks...car frames ect....any ways he has gone out of busines. but i have been doing my own blasting for several years. i am aware of cfm and psi but what im looking for is some one to maybe share with me what there system is and the size of there compressure and blasting pot. i will be doing out doors blasting for now and no neighbor problems.
chris
Posted by Bob Stephens (Member # 858) on :
Dont mess around with anything but a portable deisel unit. Buy a used ingersol rand for $2-3k from a rental place. They put out constant 100 c.f.m. or more and you can blast that sign in under 30 minutes. Time is money so the faster you can blast the sooner you can get on to other work.
You can do fine with a 100 lb pot but go the extra bucks and get a 200 lb. You wont have to stop and fill up as often.
I think I paid $2,500 for my compressor and another $1200 for the pot. Great setup and I can blast damn near anything I want.
Oh and another thing. Spend the $100 on a carbide nozzle.. Dont waste your money on the ceramic tips. They'll wear out real fast with a serious setup.
[ January 17, 2005, 05:11 PM: Message edited by: Bob Stephens ]
Posted by Amy Brown (Member # 1963) on :
Chris,
Listen to Bob. We have a 7 HP Two stage 80 Gallon compressor and a 90 lb. pot and it takes damn near forever to blast signs that are big.
I don't even want to blast anymore because I don't want to risk my health plus I'm not really supposed to be doing it here in my neighborhood. Not to mention it takes damn near forever.
Did I mention it takes damn near forever! HE HE! Good luck.
[ January 17, 2005, 05:41 PM: Message edited by: Amy Brown ]
Posted by Belinda Palmer (Member # 4628) on :
Chris, Bob is right. We already went down the road you are on and way too much money later we have a "large" system that works well on smaller projects. C & B
Posted by David Wright (Member # 111) on :
Honestly, when I read the title of this post I was thinking, isn't that kind of messy and should be done at the shop. In house. Posted by John Arnott (Member # 215) on :
Chris, don't do it! If you still want to, do exactly as Bob said. I got rid of my equipment (5 H.P. pressure tank, life support system, etc.) Its not worth it unless you go big time. I sub it out and have no more headaches! John
Posted by Rick Sacks (Member # 379) on :
The compressors you're considering are great for spraying paint, but won't even really keep up with an air sander, let alone a blaster with a 1/4" nozzle. The smaller tips are hard to get even blasts from because they cover such a small area. Go big or sub it out.
Posted by jack wills (Member # 521) on :
I hear there was some Blasting... in the Outhouse!
CrazyJack
Posted by Tom Bahr (Member # 2925) on :
Dido what Bob said. I blast cedar, granite, & boulder signs using this settup. But, I would recommend renting the equipment: diesel compressor, hose, nozel, hood, replacement lenses for the hood, pressure pot(100lb is easier to lift in & out of the truck than a 200 or 300, & have them throw in an extra air hose that hooks up to the compressor to blow off your material & you & every thing else that gets full of sand. A one day rental for all of this runs about $140 here. Take this to a remote site in the country & have at it. You can really get the work done. Then if you think you need to own one, you'll be sure.
Posted by Bill Dirkes (Member # 1000) on :
Ditto what Bob said, except for one thing. I have everything I need in house to blast away, except the big tow behind compressor. I can rent that for $65/day or $180/week. I'm not a mechanic and these beasts are touchy. It's all too easy to spend half a day working on the compressor to blast for a couple of hours. (ask me how I know) If the rental fails I take it back and get another one. (BTW that's never happened) I blast about 8-12 times a year.
Posted by Chris Lovelady (Member # 2540) on :
thanks for all the great advise i think i will proably rent...i have such a lust to buy the equipment. mine, mine , mine....but logic overrules again.
thanks again.
chris
Posted by John Deaton III (Member # 925) on :
Ive been getting my blasting done by a monument company, but hes too far away. About 60 miles one way. So I am like Chris, Ive gotta consider getting a setup to do it here. I built a blast booth that I can do up to a 4x4 in, but my compressor, a 6hp single phase unit, dont put out the cfm needed to blast really good. I either gotta get my own equipment, or quit offering blasted signs at all.
Posted by Chris Lovelady (Member # 2540) on :
well...here is the update..i can rent the 185cfm compressor but no blasting pot...something about liablity or some thing...so i have ordered the blasting pot will rent the compressor and see how it goes...still want the compressor but that will have to wait. a booth is some thing i will have to consider building and if i want to reclaim the blasting product like my friend who blasts glass does. he has 2 compressors in series. but a small booth. he has done some small stuff but say he would rather not mess with the hdu and grain frame ect...
thanks again for all the great advise!
chris
Posted by Dave Sherby (Member # 698) on :
I wouldn't consider blasting a sign that size with anything less than a quarter inch nozzle. You'll need 100 cfm minimum.
You're on the right track buying the pressure pot but renting the compressor. Get yourself a good Bullard fresh air hood and get it set up right. If you're blasting outside, you'll probably be using sand and silicosis is nothing to fool around with. Buy a fresh air turbine for your air supply and enough hose to keep it well away from your blasting area.
Also buy enough hose to get the compressor far enough away too. If it starts sucking up sandblast dust and starts eatingup the machine, your rental place won't be to happy with you.
A 150# pressure pot will do. 200# would be better, but I find after a 100# bag of sand I'm ready for a short break anyway. The main thing is go with a 1/4 inch tip, boride or carbide, not ceramic. They're about $100 but worth it. Make sure it's the venturi type and not the straight bore. A venturi nozzle makes a bigger and even pattern. A straight bore has a high concentration of sand in the center of the blast pattern, much less at the edges. It really helps in getting a more even blast, and gets rid of more material faster.
Posted by Todd Gill (Member # 2569) on :
Dave - explain silicosis please. I've heard the term in relation to blasting but can't say as I know exactly what it is or how it might affect a person healthwise. Thanks.
Posted by Dave Sherby (Member # 698) on :
Silicosis is a nasty disease that attacks the lungs as a result of breathing in free silica. It produces fibroids in the lungs, shortness of breath, suseptability to TB & lung cancer. It is similar to black lung disease but doesn't take nearly as much exposure to free silica as coal dust.
The free silica that gets you is too small to see. You have to wear a fresh air supplied hood while blasting. I wear it even while I fill the pot. When you pour that stuff you may notice what looks like white smoke drifting out of the pot. That is silica dust that can be inhaled.
Free silica also gets airborne when you drive down a gravel road, cut concrete, grind stone. They don't know how much exposure it takes to develop silicosis, but they do know that industrial exposure quickens it considerably. But it's still a crap shoot because everyone is different. Some smokers get lung cancer in their 50's, some people smoke into their 90's without ever getting it.
Forgot this story. My blasting supplier told me the reason they started enclosing and air conditioning farm tractors was because the farmers were breathing in too much free silica from tilling the soil.
[ January 20, 2005, 12:19 PM: Message edited by: Dave Sherby ]
Posted by Todd Gill (Member # 2569) on :
Thanks for that information Dave....I've only blasted a couple signs...but I didn't realize that "smoke" dust could be so hazardous.
A filtered mask or dust mask won't suffice? You have to have an air supplied hood for maximum protection?
I have a blasting project I want to do this spring (for myself) and am wondering if there is a less expensive alternative for occassional blasting?
Thanks again.
Posted by Dave Sherby (Member # 698) on :
Most dust masks are made for non toxic dust. An air supplied hood is the only safe way to go. I also take the following precautions. I only blast when it's windy with the wind blowing away from the shop. I'm in a wooded area full of sand with nobody living close by.
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