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Compressor/CFM/Sandblaster ?????

2K views 9 replies 4 participants last post by  PAToyota 
#1 ·
Here is what I have:
26 gallon husky 6 cfm @ 90 PSI
25 gallon Coleman 6 CFM @ 90 PSI
60 Gallon IR 11 CFM @ 100 PSI

I just bought a new Snap On sandblaster that needs 21 CFM @ 100 PSI to be 100% efficient. Is there any way I can link the 3 compressors to give me greater CFM at a given PSI?
 
#2 ·
Well, linking the three of them in parallel will increase your cfm but the 90 psi is going to be your limit if that is the max psi for the two compressors.

Say you had three identical compressors at 100 psi and 6 cfm. Put them all in parallel and you'd get 100 psi at 18 cfm and you just run them all directly into a common pipe to connect the three.

Now say one (or more) has a lower maximum psi than the others like you have. You're going to have to put a one-way valve on the lower psi machine so that it doesn't see the higher psi. This also means that when it gets to its max psi it is going to shut down. So the two 90 psi machines are going to shut off at 90 psi and only the 100 psi machine is going to be working to get it up to 100 psi so you're back to the 11 cfm for max psi.

Now if all three of them have a max of (say) 120 psi and the 90 psi is just their rating you're just going to be dropping after that 90 psi - maybe 5 or 4 cfm at 100 psi for them. Which basically means that you're under the 21 cfm you required. But consider that you will have 111 gallons of capacity so that will give you a margin - you just won't have 100% duty cycle on the sandblaster.
 
#4 ·
PAToyota said:
Well, linking the three of them in parallel will increase your cfm but the 90 psi is going to be your limit if that is the max psi for the two compressors.

Say you had three identical compressors at 100 psi and 6 cfm. Put them all in parallel and you'd get 100 psi at 18 cfm and you just run them all directly into a common pipe to connect the three.

sandblaster
This sounded good and we built a 1" manifold. All 3 compressors are parallel and all 3 now run the same PSI: 120+. At the manifold we get 120+ and at the blaster we get 120+. Once we turn the blaster on we get a steady drop down to 60 PSI over 2-3 minutes of continious use of the blaster. The drop at the blaster is 5 lbs more than at the manifold due to the hose/connections.

Bottom line is that we dont have enough pressure/cfm to run this POS blaster.
 
#5 ·
It should work? I think you'd want to run them all off the same pressure switch or you'd have caos :D It's gonna draw some serious power too, and the start up spike is going to be brutal :D

If you're getting a severe pressure drop at the blaster, then it sounds like you just need larger lines, fittings, manifold, etc.

I use a 3/8" quick connector to feed air from my compressor to my hard lines. It moves A LOT of air. For this setup, you may need even more than that, I dunno!
 
#6 ·
As i understand it what we did was build a giant tank with 3 pumps. All 3 tanks run into the manifold w/ a pressure switch on the all the POS 'pressors. All compressors stay at the same pressure within a pound or 2.

We have 112 gallons of capicity and 3 pumps that put out a combined 22.2 CFM @ 100 PSI. The blaster requires 21 CFM @ 100 PSI. WTF? I can maintain 65ish PSI with all 3 running. The compressor gauge falls at about the same rate as the blaster gauge so our supply lines are about the right size.

This is pissing me off. Thank you; drive through
 
#7 ·
CanuckJeeper said:
Not to mention the headaches of hooking up all these compressors on a home wiring circuit! :flipoff2:

JP
Ahhhhh, yeah. My home wiring circuit is 3 phase with delta Y. I can run just about anything I want :flipoff2:
 
#8 ·
dd113 said:
We have 112 gallons of capicity and 3 pumps that put out a combined 22.2 CFM @ 100 PSI. The blaster requires 21 CFM @ 100 PSI. WTF? I can maintain 65ish PSI with all 3 running. The compressor gauge falls at about the same rate as the blaster gauge so our supply lines are about the right size.
Probly something like nominal air requirement on the blaster vs. fudged, absolute maximum output on the compressors when new. That would be my guess. Better add another pump :D
 
#9 ·
CrustyJeep said:
Probly something like nominal air requirement on the blaster vs. fudged, absolute maximum output on the compressors when new. That would be my guess. Better add another pump :D

Cool, I get to spend even more money. I agree that the writtten amount of output vs the actual amount is different. It is kinda cool. I have about 15' of compressors and at least 50' of line not doing what I need it to do. The best part of all of this is that it cost a lot of money and took a bunch of time to not work. That is so much better than when you try a cheap and fast fix and it does not work.:mad3:
 
#10 ·
dd113 said:
We have 112 gallons of capicity and 3 pumps that put out a combined 22.2 CFM @ 100 PSI. The blaster requires 21 CFM @ 100 PSI. WTF? I can maintain 65ish PSI with all 3 running. The compressor gauge falls at about the same rate as the blaster gauge so our supply lines are about the right size.
I'm surprised that it drops off that quickly. Also consider that the two small compressors are 6 cfm at 90 psi - so probably about 3.5 or 4 at 120 psi... And drop that 11 cfm down to 10 or 9 at 120 psi.

I had figured that the 112 gallon capacity would give you a longer duty cycle. My two-stage 5hp compressor with 80 gallon tank puts out about 18 cfm at 100 psi. The compressor runs quite a bit, but it actually cycles while I'm sandblasting.

You may want to try a smaller size nozzle in the sandblaster to get a lower required cfm.
 
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