CFM to a blast cabinet

[Desert rider]

I know, when it comes to Air Compressors, Bigger is Better, BUT…
My SpeedAir 30 gallon compressor has a 1/4 in pipe connection from the tank output to the Pressure switch and it’s distribution manifold is all 1/4 inch brass… Everything down stream from there is 1/2 inch brass, copper and Black Iron…. My question is, is my CFM limited by that one 1/4 inch restriction At the tank, no matter what is downstream?

 

[dr_clyde]

Yep.

 

[mike93lx]

A single restriction doesn't take the whole system down to effectively that size. It's hurting and you could help yourself by upsizing.

Problem is that you'll just empty the tank faster and won't extend run time

 

[rlitman]

I know, when it comes to Air Compressors, Bigger is Better, BUT…
My SpeedAir 30 gallon compressor has a 1/4 in pipe connection from the tank output to the Pressure switch and it’s distribution manifold is all 1/4 inch brass… Everything down stream from there is 1/2 inch brass, copper and Black Iron…. My question is, is my CFM limited by that one 1/4 inch restriction At the tank, no matter what is downstream?

Nope, it's worse than that, because you've got a 1/4" tee feeing two quick disconnects that are even smaller. The 1/4" should be ok to outpace your relatively small compressor, so it's fine, but having a QD at both ends of your hose is holding you back. Hard plumb your manifold without the QD in the middle. If you need to use hose clamps and barbed fittings, that's fine. Or use something with a swivel.

 

[dr_clyde]

A single restriction doesn't take the whole system down to effectively that size. It's hurting and you could help yourself by upsizing.

Problem is that you'll just empty the tank faster and won't extend run time

Yes and no.

It absolutely restricts how much volume is coming through the single orifice. The pipework itself won’t be as restrictive if it then gets bigger again, but having a 1” pipe coming out of a 1/4” connection doesn’t flow nearly as well as 1” to 1”.

The pipes themselves do restrict flow, and having bigger pipes does help with the pressure required to push a given CFM, but a small restriction is analogous to a partial clog.

 

[mike93lx]

Yes and no.

It absolutely restricts how much volume is coming through the single orifice. The pipework itself won’t be as restrictive if it then gets bigger again, but having a 1” pipe coming out of a 1/4” connection doesn’t flow nearly as well as 1” to 1”.

The pipes themselves do restrict flow, and having bigger pipes does help with the pressure required to push a given CFM, but a small restriction is analogous to a partial clog.

We aren't disagreeing on any of that

 

[Steve_P]

I replied to this earlier and now it's gone. Strange. Anyway, part of my reply was that a 1/4" orifice will flow >50 CFM at 100 psi; so that's not the issue.

But I think where the OP is going, is that if you are trying to run a blast cabinet, you need at least a 240V 15A compressor with a 60 gallon tank; and even this is marginal with a 3mm nozzle. So the short answer is that if your compressor isn't at least this big, you're not going to get a lot of blasting done, no matter what piping system you have.

 

[strutaeng]

Agree with @Steve_P Media blasting takes an enormous amount of air. And it's really dictated with the nozzle size.

You need a very large compressor, like 7.5-10 HP or larger to get some decent work done. Maybe in a cabinet a 5 HP is okay for small parts?

The folks that do media blasting for a living use those large diesel tow behind compressors for a reason.

 

[Steve_P]

Agree with @Steve_P Media blasting takes an enormous amount of air. And it's really dictated with the nozzle size.

You need a very large compressor, like 7.5-10 HP or larger to get some decent work done. Maybe in a cabinet a 5 HP is okay for small parts?

The folks that do media blasting for a living use those large diesel tow behind compressors for a reason.

Siphon blasting in a cabinet uses less air than a pressure pot; but it still uses a lot of air. I cabinet blasted for many years with the compressor specs that I mentioned. But the compressor ran nearly nonstop, I had a box fan on the pump, and I'm surprised that I never melted the damn thing down. I replaced that compressor with a 7.5 HP Quincy QT7.5; this has more than 2X the CFM of the prior compressor and will actually keep up with a pressure pot blaster using a 3mm nozzle.

 

[isb cornbinder]

My brother had a large wood working shop. Rather than plumbing in a large air storage tank, he had his contractor install two inch or larger pipe. His storage in the distribution piping was greater than 80 US gallons. After his compressor there was a refrigerated air dryer and a small surge tank.

 

[dnschmidt]

Here we go again. Physics hasn't changed since the BIG BANG! For a blast cabinet you need 7.5 HP 80 gallon tank. It's always been that way and it will always be that way. This question has been asked and answered at least 1,000 times on this board.

 

[PoorUB]

5 to 10 HP would be great, but for a weekend warrior you can get by with less. I have blasted a fair amount with a 2 HP compressor, but you blast and wait, blast and wait. 5 HP is really about the minimum. Depending on the blast cabinet you may still have to wait. A blaster with a small nozzle the 5 HP will keep up.

A friend had a 3 HP compressor and a small blast cabinet and it would almost keep up. For his use he was satisfied with it.

It is really hard to say not knowing the specs on your blaster.

 

[mike93lx]

My brother had a large wood working shop. Rather than plumbing in a large air storage tank, he had his contractor install two inch or larger pipe. His storage in the distribution piping was greater than 80 US gallons. After his compressor there was a refrigerated air dryer and a small surge tank.

You would need 500 feet of 2" ID pipe to get to 80 gallons. That is a big shop and a lot of money in piping. What material was it piped in?

 

[GeoBruin]

Here we go again. Physics hasn't changed since the BIG BANG! For a blast cabinet you need 7.5 HP 80 gallon tank. It's always been that way and it will always be that way. This question has been asked and answered at least 1,000 times on this board.

It's only been asked and answered 1,000 times because people make knee-jerk replies to old threads that are reawakened. Kind of like this one...