Help choosing a compressor

[mordzy]

Hi all.

Firstly i already have a compressor. - clarke 100l 14cfm. (machine mart)

i have the usual tools, air ratchet gun, drill, sander, die grinder. all for home garage use.

Recently i have got into some restoration of old stuff which requires some blasting. i picked up a portable blasting hopper and also a small blasting cabinet. been trying to remove paint with ally oxide and also glass beads. however its slow work.

My assumption being that the compressor don't have enough FAD. or that the CMF rating of 14 is on the piston not the FAD.

Anyway. i need to know what wold be the best thing to get for such work. the compressor always seems to be running when I'm blasting too.

from what i have looked online I'm limited to around 20 CFM FAD on single phase. and only have a 40 amp feed to my garage.

is it worth looking at a 3 phase unit that can do more cfm fad? will 40 amp be enough to run one...

lots of questions.

Thanks in advance.

 

[tigler]

Basically blasting is a big air leak ! 14 CFM even if it's FAD isn't enough for continuous blasting, the clue is the compressor running continuously.
30 CFM FAD is a minimum really, and more if poss. Thats about a 7.5 to 10 HP motor, so 5 to 7.5 KW. If you have a 40 amp 3 phase feed thats enough. You could either get one big compressor or add another to your existing compressor to supply enough air for blasting. Then you could just use the smaller one for other jobs when less air is needed.
Alternatively a petrol or diesel powered compressor could be used for blasting.

 

[rtbcomp]

I use a 3hp and a 2hp together to supply a blast pot, they do run continuously. If you have a "blasting hopper" that sounds like it's a siphon gun which uses much more air than a pot.

Also I'd switch to a more aggressive media such a J-Blast Supafine or crushed glass grit. Certainly glass beads are totally unsuitable for blasting paint off, they are used to get a smooth finish ready for polishing.

 

[mordzy]

thanks guys. just saw someone else's post about joining. that may be the way to go.

my 40 amp feed is single phase but i have seen kit on ebay that makes 3 phases out of the single (I'm no sparky) but not sure if 40 would be enough to run one big compressor.

I have seen a few older ones on ebay that look ok / single and 3 phase. but because they are old they don't have a cfm rating.

yes my blast cab and pot are syphon - all clarke gear. I'm new to air tools and blasting so took the advice of machine mart. even the noise of the direct drive one i have is starting to do my head in

 

[tigler]

Don't bother with the phase converter on a big compressor, lots of potential problems.
The 40 amp feed gives you a capability upto 9.6kw. Another option is a tandem compressor, that is 2 compressors on one receiver. Then you could switch one off when you need less air. When looking at older compressors with no quoted CFM, look at the motor power, rule of thumb is about 4-5 CFM per HP and 1 HP = 0.747 KW.

 

[rtbcomp]

took the advice of machine mart - Should have gone to Mig-Welding.co.uk

Belated welcome to the forum BTW!

 

[mordzy]

took the advice of machine mart - Should have gone to Mig-Welding.co.uk

Belated welcome to the forum BTW!

yeh thanks for that

i have seen the dual motor compressors but again they only seem to chuck out 25 cfm. if i can get 2 second hand ones that are doing 16-17cfm ill be better off i think.

i take it the screw/hydrovane type compressors are for quiet running rather than FAD. the 240v ones i have seen only do 5cfm

this is the biggest twin i have seen.
http://www.machinemart.co.uk/shop/product/details/se29d270-ol-air-compressor

but for the money i could by 2x SE16C150 off of ebay for less.

 

[tigler]

Hydrovanes are made as big as you want them ! They do like continuous running, actually they are designed with that in mind. More critical about servicing though, the parts aren't cheap and a specific oil MUST be used.
Probably. Air for blasting isn't cheap, it's just about the heaviest demand application there is. The pro's use screw units because they're quiet and can produce massive amounts of air, but they are far from cheap ! Also, the larger versions are almost always 3 phase.

 

[clueless77]

yeh thanks for that :asham

this is the biggest twin i have seen.
http://www.machinemart.co.uk/shop/product/details/se29d270-ol-air-compressor

but for the money i could by 2x SE16C150 off of ebay for less.

i got that one at a vat free sale, not done any blasting with it yet but it's good at everything else. just need to buy one of them 20 gallon pots to do my steel wheels.