How to size air Compressor for Shop

nitrousmudbogger · Apr 17, 2018

We have 11 CNC's running on the day shift and seem to always have air issues. I have 2 Kaeser compressors that are 88cfm ea, I have another kaeser that is 190 cfm or so. We have 2 250ga air tanks

I only run the small two or large one at a time but always have issues.

When the two small ones were new everything was great, now with about 7000 hrs on them I cant seem to keep going if someone is sand blasting or something on top of the machines.

How do you size the air needed for a shop, also the lines, tank capacity etc?

DDoug · Apr 17, 2018

Sounds like you could well afford to put in some flow metering.

How many leaks ?

This sandblasting operation, how much CFM ?

Pull hard on that (during sandblasting), and if you drop the plan't air down to 80 psi or so, you run a real good risk of machines shutting down, ruining parts, etc.

JRIowa · Apr 17, 2018

Each machine manual should have a CFM requirement in the manual. You also don't say how big you shop is. You'll need to know the runs for total length. Just guessing, but you probably need another tank. You probably have blow-off lines at every machine also. Do you run secondary operations that also use air?

Lots of unknows! When you have the blanks filled out, go here: http://www.industrialaircompressors.../how_to_determine_Pipe-Size_chart_2-18-11.pdf

You'll probably need to run a large main line either down the center of the shop or in a loop around the shop. I'll guess at least 3". You might find out as we did years ago, it was cheaper to put an 80 gal tank at each machine than to re-run air lines.
JR

PackardV8 · Apr 17, 2018

There are on-line calculators which require knowing entering the CFM requirement of each tool and each machine. Do the work and the answer will appear.

My guesses?

1. You may have a worn blast nozzle. Not changing blast nozzles regularly can double the CFM used in a cabinet.

2. Put a guy with a brush, a jar of soapy water and a shirt pocket full of red tags going from compressors to the end of all of the lines. You'll be amazed at how many leaks he finds. QD connectors wear, hoses develop leaks, coil lines kink; it all is cumulative and should become part of your regular maintenance. It can vastly increase the life of the compressors and even lower your electricity bill.

jack vines

jack vines

bloomautomatic · Apr 17, 2018

Sandblasting takes a lot of air and it's based on the nozzle size. Whatever size nozzle you're using will erode out to the next size up, so use that as your number. A 5/16 nozzle at 100psi will use about 140cfm.

Sandblasting Nozzle Air and Pressure Requirements Chart - Sandblasting Nozzles

I'd look at that and the machine requirements to see what you're theoretically using. If it's more than the compressors can put out, there's your problem. If not, look for leaks or undersized lines. For sandblasting you probably want a 3/4" pipe or larger. Hard pipe it as far as you can to avoid losses from rubber hose.

When I need to size a compressor, I call my distributor and have him come in to look at the operation. I've had them do monitoring on it to see how much air we're using and what the demand is. That will really tell you what size tank you need to support it. I buy big compressors, so they do this for free for us.

If you're sandblasting small parts in a booth, a smaller tank could help keep up with it. If you're blasting plates where it's wide open for 10 minutes at a time, that will deplete the tank and it's up to the compressor to keep up.

For the most part, the biggest tank you can afford or fit will give better results. Putting a tank near your sandblaster may help with the surge also.

nitrousmudbogger · Apr 17, 2018

Our sandblasting is not common, We maybe blast once a week for 5 minutes with the occasional once a month for couple hours

nitrousmudbogger · Apr 17, 2018

After reading the line size chart im thinking that is it. We only have 3/4 line and necked down to 1/2 in places for some machines. Im guessing it would be like blowing through a straw for our compressors and back pressuring them to work harder to speed up the air

nitrousmudbogger · Apr 17, 2018

To help you guys we have
Two Daewoo MX2000ST mill turn machines
1 Doosan 6300 630mm Horizontal Mill with 7 pallet pool
1 Doosan HP4000 400mm Horizontal
1 Doosan HP5100 500mm Horizontal
1 Haas EC 400 pallet pool horizontal
1 Kiwa KNH400 pallet pool horizontal
3 sharp mini mills
1 haas vf3
1 haas mini mill
Romi cnc lathe
Sharp cnc lathe
other misc support machines
machine Shop portion is about 80x80 feet

JRIowa · Apr 17, 2018

3/4" line????

The list doesn't help without CFM for each machine and a shop lay-out. That's your job or a Co-op. Don't know if a 3" perimeter line or a 4" down the center makes more sense. You or someone needs to do the engineering on this. Asking a bunch of guys that don't know your shop or operation is like pissin' in the wind.
JR

Cwalster · Apr 17, 2018

nitrousmudbogger said:
To help you guys we have
Two Daewoo MX2000ST mill turn machines
1 Doosan 6300 630mm Horizontal Mill with 7 pallet pool
1 Doosan HP4000 400mm Horizontal
1 Doosan HP5100 500mm Horizontal
1 Haas EC 400 pallet pool horizontal
1 Kiwa KNH400 pallet pool horizontal
3 sharp mini mills
1 haas vf3
1 haas mini mill
Romi cnc lathe
Sharp cnc lathe
other misc support machines
machine Shop portion is about 80x80 feet

Somethings not right here - last shop I worked at ran 9 Haas mills off a pair of 15 CFM compressors. They were fine with that load plus two die grinders (third grinder would cause intermittent issues).

Unless your using air blasts non-stop, CNCs tend to be more intermittent loads. The Haas's were rated at 4 CFM, but would be fine on 3ish CFM pancake compressors as long as the tank was large enough and you spaced tool changes out (I don't recommend that, but when you have to make parts...) Check your machines air requirements, then go testing. I'd guess something is drawing significantly more air than it should be or you have some restriction/leakage problems. Air grinders and blow-off nozzles are huge air hogs, don't underestimate those.

Cole2534 · Apr 17, 2018

In conjunction with leak testing, I'd be watching with a gauge for pressure drop.

Find the tail end of the system, or a few other points, and hang some gauges on the line to see how your loading of the system has an effect on pressure at various points.

DDoug · Apr 17, 2018

nitrousmudbogger said:
To help you guys we have
Two Daewoo MX2000ST mill turn machines
1 Doosan 6300 630mm Horizontal Mill with 7 pallet pool
1 Doosan HP4000 400mm Horizontal
1 Doosan HP5100 500mm Horizontal
1 Haas EC 400 pallet pool horizontal
1 Kiwa KNH400 pallet pool horizontal
3 sharp mini mills
1 haas vf3
1 haas mini mill
Romi cnc lathe
Sharp cnc lathe
other misc support machines
machine Shop portion is about 80x80 feet

....and no listing for the sandblaster....it could just be the biggest user
in the whole shop.

dstryr · Apr 17, 2018

Is the system looped? Where is the storage?

DDoug · Apr 17, 2018

nitrousmudbogger said:
After reading the line size chart im thinking that is it. We only have 3/4 line and necked down to 1/2 in places for some machines. Im guessing it would be like blowing through a straw for our compressors and back pressuring them to work harder to speed up the air

Uh...no.

Compressor just makes air at what ever the switch/unloader is set at.

How much get's thru the pipe is a simple function, and the compressor
doesn't "compensate by working harder".

nitrousmudbogger · Apr 17, 2018

Im not asking for anyone to do the math just incite. If the manufactures calculate air like they calculate max load for electricity I will need about a million cfm
The doosans eat a lot of air, I will see what I can find in the books, they also have air blasters on the conveyors to blow chips off the back side of them.
As I said earlier we do not use the sand blaster an average of one hour per week, so that is not my biggest concern

Cole2534 · Apr 17, 2018

digger doug said:
Uh...no.

Compressor just makes air at what ever the switch/unloader is set at.

How much get's thru the pipe is a simple function, and the compressor
doesn't "compensate by working harder".

Kinda what I was wondering about. So much differential across the system that the compressors reach discharge setpoint and unload while the down stream system is starving.

If this is the case it >should> show up with some gauge testing. From there you can choose to run larger trunk line(s) or possibly set receivers to help surge capacity.

Since we're talking about compressors, here's one I was around a few weeks ago. 333rpm integral.

dstryr · Apr 17, 2018

I was having similiar problems to you but I have more machines. What I ended up doing was moving my air storage and re piping the compressor to both air tanks with 1.250" copper and bridging it into the 3/4 system. It seemed to fix the air drop issues.

nitrousmudbogger · Apr 17, 2018

do you want air storage away from the compressors or near

dstryr · Apr 17, 2018

If the system is looped it shouldn't matter. I put them near the compressor to save on piping with the 1.250 copper

nitrousmudbogger · Apr 17, 2018

not looped, looks like [

How to size air Compressor for Shop

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