Quiet compressor question

[CallumRD1]

I'm looking for some advise on compressor selection. I'm trying to downsize from a big (and entirely overkill) three phase Kaeser screw compressor to a less expensive piston compressor.

My needs are fairly modest: I reckon that 3 hp (at 240V, naturally) would be sufficient but wouldn't mind having 5 hp. The primary use will be running the ATC and mist coolant on a small CNC mill with the secondary use being general air tool use (i.e. blow gun, occasional die grinder, occasional air hammer, blowing out sprinkler lines, filling tires, etc.). The compressor will see intermittent use, maybe a handful of hours a week on average; it won't be running constantly in any respect.

My only additional requirement is that it be relatively quiet. This is quite important as the compressor will be in a fairly small shop that's acoustically quite loud. I figure that with my low air usage requirements it'd be possible to find something suitable. I'd like to stay under $2000 if at all possible, and cheaper than that wouldn't be a bad thing!

If you can help point me in the right direction I'd appreciate it!

 

[gizardlizard]

Check into California Air and Eagle Air silent series. We have a portable Eagle air at work we use now and then. Crazy quiet. Puts the Kaeser screws to shame. They probably won’t be cheap though

 

[finn]

Don’t overthink this. At two hours average per week, that’s around 100 hours per year, or 1000 hours in ten years.

Even the cheapest compressor should last that long.

Quincy QT compressors advertise a life expectancy of 50000 hours. I don’t know it that’s a B10 life, or B50, but B10 is what I am familiar with for commercial industrial products. That’s 50 years life for 90% of the compressors with the use you describe.

Not sure about you, but there’s no way I will still be using a compressor when I am well past 100 years old, so the $2000 Quincy would be pure overkill if you don’t include ego and bragging rights as part of the purchase rationale. Just about any three to five hp box store compressor would meet your air and useage requirements.

Noise is a different issue, though.

 

[whateg01]

I was skeptical about the California air tools compressor really being as quiet as everybody claims, but it really is. My 7x12 bandsaw is louder than the compressor. I have a bigger compressor too, but with battery powered tools taking over many tasks formerly assigned to air, it doesn't see as much use and I hate the noise. So now I use it when I need more air but for smaller tasks, I use the CAT

 

[cvairwerks]

What are the consumption figures for the ATC and mister? Those are going to set your main needs for sizing.

 

[RTM]

I always thought a screw compresso was always quieter than a recip of the same size, at least at large sizes 30 years ago when I last worked around them?

My little CAT is way quieter than my similar sizes PC pancake, for those (unlike whateg01) who are still skeptical

 

[gizardlizard]

Screws are quiet but the new recips that are speciality models for quietness are even more quiet. Just pricey

 

[GeoBruin]

The only two ways to get "quiet" is by going with one of the quiet oilless compressors (such as the CAT described above), or with a big, slow turning, oiled recip compressor with lots of baffling on the intake.

The former will be limited in air delivery unless you step up to one of the models where they bolt multiple motors/pumps to the same tank in a cabinet but at that point, you're spending more and taking up as much room as a 5HP with a 60-80 gallon tank.

The latter option gets expensive pretty quickly. The Eaton/Polar air get mentioned frequently here. Here is a link to the model that falls just outside your price range.

The other option no one talks about but is exceedingly practical, is to get multiple CAT style compressor and plum them in line. You can use just one when you just need a little air, and engage the second (or third) when you need more flow. If one of them is a portable variety, it also give you the flexibility to have one on the go.

Good luck!

 

[tarbellb]

This exactly ^^^

I would consider plumbing several smaller (30g?) inline.

With HF and Kobalt offering nice, cheap options this could be a good way to achieve what your goal.
And if pre planned could also have a portable option.

 

[theoldwizard1]

We really need to know max PSI and CFM. Also duration. If duration is short (a couple of minutes) you can get away with a smaller compressor and an extra storage tank.

More than a couple of minutes with a die grinder will eat up a lot of reserve. Sandblasting takes a lot of CFM and time?

 

[CallumRD1]

Thanks for all the input everyone! This has been very helpful. My requirements for the mill are very minimal, a handful of cfm on average. The current ~30 cfm Kaeser 7.5 compressor runs on a 10-15% duty cycle when the mill is running with frequent tool changes and the mist coolant on full tilt.

I don't have a blasting cabinet at the moment but there's potential for one in the future. I guess that could be the one thing that pushes me beyond what a 5 hp compressor can supply.

I'm really liking the look of the Eaton Polar quiet compressors that were recommended. ~$2150 for the 5 hp and ~$2700 for the 7.5 hp.

One thing that does concern me is the start-up current draw that a 7.5 hp piston compressor could demand. The current 7.5 hp Kaeser screw compressor doesn't spike on startup so it's not a concern but currently the electrical feed to my shop is rather limited given everything else that's often running. Does anyone have any experience for what the start-up current draw requirements for compressors like the Polar 5/7.5 hp models could be?

 

[mogandave]

So you want to downsize from a 7 1/2HP screw to a 5HP piston and you want to add a blast cabinet?

Is something wrong with the screw?

 

[cvairwerks]

You need to stop fixating on the compressor drive horsepower and look at your pressure and flow needs. These will drive what size compressor you need to be looking at. You are going at this completely backwards.

Pull out the books and see what they say the ATC needs for pressure and flow, then see what the mister uses. The spec should be something like x CFM @ Y psi....

 

[CallumRD1]

So you want to downsize from a 7 1/2HP screw to a 5HP piston and you want to add a blast cabinet?

Is something wrong with the screw?

The Kaeser 7.5 is just way too much machine. It's a $12,000 compressor (plus a phase converter to feed it 3 phase power) that the person I share a shop with purchased about 2.5 years ago and we've only put ~200 hours on it over that time. It's both a lot of capital sitting *******, not cheap to maintain, and a financial liability if something broke on it. We'd rather sell it and move into a much less expensive setup.

The blast cabinet was only brought up because the person I share a shop with has expressed interest in maintaining the ability to get one in the indeterminant future, not because there's an immediate need for it.

You need to stop fixating on the compressor drive horsepower and look at your pressure and flow needs. These will drive what size compressor you need to be looking at. You are going at this completely backwards.

Pull out the books and see what they say the ATC needs for pressure and flow, then see what the mister uses. The spec should be something like x CFM @ Y psi....

I haven't been fixated on horsepower in any sense. I've only used it to describe models as a descriptor and a proxy for air output (most compressors produce 3.5-4.5 cfm per hp).

In my last post I described the mill air requirements as running a ~30 cfm compressor at a 10-15% duty cycle when running with frequent tool changes and the mist coolant on full tilt which would put it at 3-5 cfm average consumption. In my first post I also mentioned that the secondary use was general air tool use (i.e. blow gun, occasional die grinder, occasional air hammer, blowing out sprinkler lines, filling tires, etc.).

 

[dnschmidt]

I find this either amusing or amazing I'm not sure which. To me having a Kaeser screw is like having a great *********. Quiet, capable, can run forever it's the holy grail. It's like finding a diamond and preferring a lump of coal. The Eaton with silencer are nice machines but they sure as hell aren't a Kaeser. I'm sort of dumbfounded.

 

[GeoBruin]

I don't know why everybody's giving him such a hard time. It's not inconceivable that you would sell a big expensive compressor, buy a smaller compressor that still suits your needs, and put the balance toward something else that you need more. It may not be the Garage Journal way, but it seems reasonable.

 

[CallumRD1]

I find this either amusing or amazing I'm not sure which. To me having a Kaeser screw is like having a great *********. Quiet, capable, can run forever it's the holy grail. It's like finding a diamond and preferring a lump of coal. The Eaton with silencer are nice machines but they sure as hell aren't a Kaeser. I'm sort of dumbfounded.

If I had a use case that could even remotely take advantage of what the Kaeser can output I might feel differently, but we're just not using it. We've only put 200 hours on it in 2.5 years. We're not running a shop with air tools being constantly used; the Kaeser pretty much only gets turned on when the mill is running and it only runs at a 10-15% duty cycle for that. The idea is that we could downsize to a piston compressor that does everything we could want, put quite a few thousand dollars back in our pocket to use elsewhere, remove the high running costs of the Kaeser, and remove the potential financial risk of multi-thousand dollar repairs on the Kaeser (which as I understand it is actually a bigger concern given how little it gets run).

Maybe I'm slightly mad, but this doesn't seem like a rediculous option to me. I'm always open to hear other opinions though.

 

[dnschmidt]

If I had a use case that could even remotely take advantage of what the Kaeser can output I might feel differently, but we're just not using it. We've only put 200 hours on it in 2.5 years. We're not running a shop with air tools being constantly used; the Kaeser pretty much only gets turned on when the mill is running and it only runs at a 10-15% duty cycle for that. The idea is that we could downsize to a piston compressor that does everything we could want, put quite a few thousand dollars back in our pocket to use elsewhere, remove the high running costs of the Kaeser, and remove the potential financial risk of multi-thousand dollar repairs on the Kaeser (which as I understand it is actually a bigger concern given how little it gets run).

Maybe I'm slightly mad, but this doesn't seem like a rediculous option to me. I'm always open to hear other opinions though.

I see your point, and it makes perfect sense, but who doesn't want to drive a Ferrari over a Toyota? That's all I'm saying.

 

[mogandave]

If the idea is to sell the screw to get as much out it as you can, while it is still reasonably new, it makes sense, but why buy a $2K compressor to use for less than two hours a week, when you may have to upgrade later?

You already have a receiver yes? Just buy a $500 three hp and be done with it. If you need more air in the future, just get another one and run both when you need to.

If you want quiet, put the compressor(s) outside or build a SG sound attenuating enclosure around it,

 

[cvairwerks]

Did a little digging.... various mister arrangements require up to about 60 psig and 3 cfm under worst case. Depending on your tool changer and drawbar, you need around 100 psig, and 6-8 cfm. So for the mill alone, you are going to need a compressor that will give you around 10 cfm at 90 psig minimum. Now whether your mill requires continuous air flow for the drawbar, I don't know, so you need to determine that. Making the assumption, that it doesn't, that would mean that any compressor that will give you the minimum of 10 cfm @ 90 psig, would meet your needs. Probably the smallest I would buy, on the super quiet side is one of the CAT 4 hp models, going up from there as you see fit to increase capacity.

If you are going to add a blast cabinet and run it for long periods, then I'd be looking at something on upper end of the hp range, maybe even one of the small scroll units, but something with at least an 80 gallon tank.

 

[tarbellb]

I see your point, and it makes perfect sense, but who doesn't want to drive a Ferrari over a Toyota? That's all I'm saying.

It's more like having a Mac Dump truck in your driveway when all you really need is a F150 pickup

loading a dozen 2x4s into that Mac ain't worth it

 

[mogandave]

It's more like having a Mac Dump truck in your driveway when all you really need is a F150 pickup

loading a dozen 2x4s into that Mac ain't worth it

No, a 7 1/5 HP screw vs a 5HP piston is more like a having an F-SuperDuty vs a Chevy Luv.

Yeah, both will carry a dozen 2X4s, and the Luv will do it cheaper.

 

[finn]

I see your point, and it makes perfect sense, but who doesn't want to drive a Ferrari over a Toyota? That's all I'm saying.

I, for one, have no interest in driving a Ferrari.

Of course I have no interest in driving a vanilla Toyota, either.

 

[CallumRD1]

I, for one, have no interest in driving a Ferrari.

Of course I have no interest in driving a vanilla Toyota, either.

I'm looking for the Lexus option in this analogy. Toyota dependability but with some sound deadening!

 

[PoorUB]

I don't know why everybody's giving him such a hard time. It's not inconceivable that you would sell a big expensive compressor, buy a smaller compressor that still suits your needs, and put the balance toward something else that you need more. It may not be the Garage Journal way, but it seems reasonable.

I have a 5HP 80 gallon Curtis I really do not need. I used to have a Porter Cable that was about 3HP that worked fine for me about 75% of the time. As I get older the need for HP is getting less. That 3HP would probably meet may needs today just fine.

The guy that bought my Porter Cable is moving and down sizing, I might buy it back and sell the Curtis. I have a 2HP 20 gallon that I really am considering using too, but I don't think it will meet my air demands.

 

[Citation]

I would consider sorting like the Eaton quite compressors. Most (all?) of what they have done is make an intake muffler for the unit. I did something similar with my belt drive 120V compressor. It really helps. It's not as quiet as my 2.3 cfm CAT but it's under the threshold where I hate to be around it.

Given you claim a 30cfm compressor is running at 10-15% duty cycle for your work I would be worried about anything under 10cfm (30-45%) duty cycle. Most of the smaller pumps say 50% duty cycle. Something like the Eaton would have no tricks with your current needs or even a blast cabinet. Note that is possible to add a DIY Eaton type air intake muffler to most compressors. That plus some sound absorbing panels may be all you need.

CAT does middle make a larger unit with 4 of their pump motor combos on it. Honestly, other than the low noise I'm not impressed with my CAT compressor. It's clearly cheap Chinese stuff paired with a legit quiet pump.

 

[dnschmidt]

I'm looking for the Lexus option in this analogy. Toyota dependability but with some sound deadening!

Brilliant answer. I liked that!

 

[toddmorr]

I see your point, and it makes perfect sense, but who doesn't want to drive a Ferrari over a Toyota? That's all I'm saying.

Because he's running a business

 

[The Tool Tyrant]

Callum, is the Kaeser a 'start-stop' machine or 'constant run'? I would assume if you're using a rotary phase converter, it's a constant run unit unless you doing a lot of running back and forth to turn the phase converter on & off.
The cost to run a 7.5 hp motor and large phase converter full time has to be quite expensive. I run a 5 man shop with 2 Haas CNC machines and LOTS of air tools on a 5HP Quincy QR 25-325 with 360 gallons of air storage (which I swear by) and have NEVER had to wait for the Quincy to catch up. The pump is super quiet especially with the intake silencer I added.
I see no need for a rotary screw machine unless you do a LOT of sand / bead blasting or have 20 CNC machines running full time.
My buddy has a large powder coating facility and runs Kaeser compressors. I was shocked when he told me the cost of 'factory maintenance' which was required for warranty.
It all comes down to common sense and cost of operation.

 

[bb29510]

sound. loudness
put a junkyard air filter on it

you tube

 

[mikeinri]

I have the same basic question, but less air need than the OP. Let me know if I should start a new thread?

My air need is limited to blow gun (cleaning stuff like a chainsaw), and topping off RV tires (my Milwaukee M18 inflator handles everything else). No air tools.

This is for home garage use, so the smaller, the better.

What is a good make/model? Cylinder vs. hot dog design benefits?

I've been reading reviews on all the box store sites, and can't seem to find ANY compressor that doesn't have bad reviews. Everything from leaking out of the box, to breaking down quickly (or right after the warranty expires)...

Budget is $300 or less.

Thanks.

Mike

 

[cannuck]

IMHO the key bit of information before choosing what to do is the comment about a blast cabinet. 5HP is a struggle. One of the shops I work in has a 15HP recip and it gets worked reasonably hard when the cabinet is being used. Suggest if this is something you are serious about install a cabinet and see how much you use it and how much run cycle time you current compressor has before selling it off. Enclosure and air inlet silencer are an option, but then you need a cooling air system. I bought a 30 HP screw for next shop and it will be installed in a separate building beside main structure for all of the above reasons. Used to run a plastic media blast system on a 40HP screw and it did quite well....the key factor being how large you blast gun nozzle is going to be.

 

[whateg01]

Blast cabinet air usage varies depending on the nozzle. To say that because the one at work used a 15 hp compressor so all blast cabinets use 15 hp is pretty silly.

 

[mogandave]

Blast cabinet air usage varies depending on the nozzle. To say that because the one at work used a 15 hp compressor so all blast cabinets use 15 hp is pretty silly.

But not as silly as a saying they need an 80 gallon compressor...

I thought cannuck's "...install a cabinet and see how much you use it and how much run cycle time you current compressor has before selling it off." suggestion was sound.

 

[cannuck]

Blast cabinet air usage varies depending on the nozzle. To say that because the one at work used a 15 hp compressor so all blast cabinets use 15 hp is pretty silly.

I guess the rumors of failed public school systems down your way are true. Reading comprehension just doesn't seem to be your strong point.