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Cubic feet per minute question about compressors

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 02/18/2010 : 20:47:19

When I purchased my soda blaster a few weeks ago, I really knew little about air tools, compressors, etc. and wouldn't profess to know all that much more now. The blaster requires about 8 CFM at 90 PSI to run properly, my compressor only puts out about 4 CFM, and even with my 11 gallon tank hooked up in series (?) as soon as I open the valve, it's only a matter of a few seconds (maybe 30-40) before the compressor's running again to catch up, and it never can, so I have to shut off the valve, and let it cycle back up.

So, I started thinking about a larger compressor, but really didn't know where to start. I was wandering around in HD or Lowes the other day, and they had some on sale, but none of them could output what the blaster required. I wandered around a bit more and found an $1800 15hp compressor with a 55 gallon sized tank that still didn't put out the required CFM at the right PSI for the blaster.

Can anyone explain to me how this is possible? I'm certain that the 15hp compressor I was looking at could keep up with this blaster, but according to it's rated output, it can't. What am I missing? Is there something I can do with my setup to increase it's volume? I know I can't change what the compressor puts out, but it would seem like having more storage would alleviate some of the cycling, but it doesn't seem to.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - on

Harleyworker
1st Mate

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USA
73 Posts

Response Posted - 02/19/2010 : 06:21:02

I checked Grainger this morning and they have quite a few that pump over 10 cfm. They have some that are 220v, 3hp, 60 gallon for $494.00 putting out 10.2 free air cfm at 90 psi. That should be plenty for the blaster. I have been wacthing your progress with the blaster, cause I plan on doing the same thing if it ever warms up enough.

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Happy D
Admiral

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921 Posts

Response Posted - 02/19/2010 : 06:33:59

It'll put out 10.2 cfm at 90 psi running 100% of the time.
Blasters require a lot of air.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 02/19/2010 : 06:39:37

http://www.princessauto.com/air_compressors

This site gives some tips on sizing, selecting, and powering compressors. Might be worth looking at.

They also list a Porter Cable Unit that might work for you, I'm just not sure if the tank is big enough to keep up... http://www.princessauto.com/air/compressors/electric/8099145-1_6-hp-25-gallon-air-compressor

Edited by - Prospector on 02/19/2010 06:41:53

OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 02/19/2010 : 07:11:38

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Harleyworker
 I checked Grainger this morning and they have quite a few that pump over 10 cfm. They have some that are 220v, 3hp, 60 gallon for $494.00 putting out 10.2 free air cfm at 90 psi. That should be plenty for the blaster. I have been wacthing your progress with the blaster, cause I plan on doing the same thing if it ever warms up enough.
<hr height="1" noshade id="quote"></blockquote id="quote">
Ditto, I own an air compressor that I purchased from Grainger and it performs great. Keep mind that since you don't make your living soda blasting boat bottoms - you don't necessarily need 100% of the suggested air flow 100% of the time . . .

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/19/2010 : 11:29:18

All the tank does is even out the flow and let the compressor cycle rather than running continuously. The compressor must keep up with demand, not the tank. Harbor Freight has a few that meet your needs, but they are 220v and not portable.

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Ed Cassidy
Captain

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USA
365 Posts

Response Posted - 02/19/2010 : 11:41:54

Something you might like to try is to reduce the size of the nozzle you are using. Soda is a very fine material to begin with and it may not need a large orifice. Secondly, I believe you can adjust the volume of air being used, along with the volume of media being use with the valves on the inlet air line and the media valve at the bottom of the tank. The valve at the nozzle is all the way on or all the way off, nothing in between to prevent it from being worn out.

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 02/19/2010 : 13:58:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave5041
 . . . but they are 220v and not portable . . .
<hr height="1" noshade id="quote"></blockquote id="quote">I purchased a 220V for two reasons:

(1) They are more efficient than 110V
(2) None of my friends have 220V circuits in their garages . . .

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/19/2010 : 16:02:09

OJ, #2 is an excellent point!

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 02/19/2010 : 17:43:45

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Harleyworker
1st Mate

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USA
73 Posts

Response Posted - 02/19/2010 : 18:52:17

I have a 220 compressor too, without a plug-in in the garage. Luckily the laundry room is just inside the garage door leading to the house. I made up an extension cord and unplug the dryer and plug the compressor in. The admiral just can't do laundry while I'm working.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 02/19/2010 : 22:16:49

Hah, I've got 220 wired in two places in my garage, and only use it for my aircraft carrier sized planer. I wasn't planning on actually buying another compressor, I can put up with the slow process on the boat even if it is annoying. I can probably rent one, it's too bad my nephew isn't closer, he's got a nice Dewalt he used when he put on my new roof a couple of years ago.

Would a larger tank alleviate some of the problem?

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islander
Master Marine Consultant

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USA
4025 Posts

Response Posted - 02/20/2010 : 07:40:00

The tank is there to maintain a constant pressure to the device that is being used while the compressor cycles on and off and eliminates 'pulsing'from the compressor. The problem in your case is not the size of the tank but rather the size of the compressor.The bottom line is that you need a bigger compressor. A larger tank really won't solve the problem.

Edited by - islander on 02/20/2010 09:20:26

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