Does this air compressor recommendation sound correct?

So here is the situation. I have a new Doosan DNM5700. It has an air curtain system and through spindle air and some other air related features. Total air usage is rated at 8.83 cfm @ 80psi. A lot of that is the air curtain which was running any time the machine is on.

My present air compressor is an Ingersoll/Rand reciprocating type, Industrial model rated at 7.5hp/80gal/29cfm. I checked the flow and it is actually putting out that rated amount.

When the machine is on the air compressor kicks on every 4:30. This is with no tool changes and no air blow nozzles and no through spindle air running. It runs for 45sec to top off. I have a small 25x25 shop. It's sheet-rocked and the sound is annoying/distracting and loud as hell. Plus it is using lots of power and getting really worked out. Bigger issue, the voltage surges are also messing with the VMC when it kicks on. By that I mean it will crash the CNC if it's actually taking a cut or doing a tool change. It is single phase and not running on the RPC the VMC is.

So I was going to switch to a rotary unit for noise alone, but now the performance issues have made it more pressing. So I called Atlas/Copco and talked to a rep about what unit to get. Told them the air usage of the VMC and the cycling issue. Also told them my other air usage. My CNC lathe uses no air so no problem there. But I do use air tools once in a while. One person, so nothing major there. That is about it. So 90% of my air usage is the VMC.

They recommended a 5hp/53gal/16.6cfm rotary unit. So smaller than my present air compressor. They said because the rotary are designed to run with a 100% duty cycle any more than that is just wasting money. Also the unit wants to be on all time it was designed for that. As to the noise factor they said these small rotary units are about as loud as a dishwasher. So huge difference there.

So does that sound right? It's not a full featured unit (electronic controls, etc.) just a standard one but still isn't cheap. I want to make this sure this sounds right to people who are actually out there with some real world experience. Thanks for your input.


TL;DR Have a 7.5hp/80gal/29cfm reciprocating, Atlas/Copco says get a 5hp/53gal/16.6cfm rotary. Is this the right size?

We used to run an ingersoll 7.5 hp 150psi piston type unit(I don't remember the CFM). loud as all get out and seemed to be

always on.if we used the plasma and the VMC at the same time, the VMC would alarm out for low pressure, cause crashes

etc...

We upgraded to a Kasier 7.5 hp 125PSI rotary unit, and we can run the VMC, the plasma and the blast cabinet

simultaneously without issue.


http://www.practicalmachinist.com/vb/general/new-air-compressor-suggestions-273141/

Heres my thread about it.

Dealing with Atlas Copco can be a challenge.

The small Atlas screw compressors do not run unloaded, so it's going to cycle just like your Ingersoll does. Which is great when it comes to power usage and keeping the hours low, but the small receiver will recharge very quickly- you might not even be able to keep the oil warm.

You want it to run for 5-6 minutes at a time, that keeps the oil warm and prevents condensate in the oil.

I have a 7.5 hp Atlas Copco GX5FF and I have it cross connected to my Speedaire recip's receiver so I have another 80 gal. of air storage. This helps to keep the compressor from short-cycling, and when it kicks on it has to run long enough to charge both receivers. If I have to run the backup compressor I shut off the valve on the outlet of the screw compressor so it doesn't see the recip, and I rely on the 80 gal. of the recip.

That 5hp will keep up, but I think you will want to cross connect your receivers so the screw compressor doesn't have to work so hard.

If I had it to do again, I would buy a Kaeser though- the Atlas is not very well made.

put in more storage first, get a quote from kaeser . Atlas copco- never dealt with them but the place with the best technical sales is the one you want to go with. I am completely happy with my 1 year old kaeser system upgrades.

Good input.

Thanks for the recommendations guys. So like they said it wants to be run constantly. So this should work out well.

Interesting the quality comment. Usually people only recommend the Kaesar, Atlas/Copco or Quincy (who are a division of Atlas/Copco). The few Atlas/Copco I have seen seem to be well made but I haven't owned one. If you eliminate them from the running it leaves Kaesar as the only brand worth buying. Seems hard to believe they have a monopoly on good air compressors.

My issue is the Kaesar is a lot more expensive to buy and the parts are pricey so they are kind of out of reach at this point with me just starting out. Budget is tight. The Atlas/Copco does have a warranty so I will hope if it breaks it is early so it's covered.

Thanks again guys.

EDIT: As to what Willie said they have been very good with the tech sales support both with the local rep and the factory guy. Very responsive to my questions and quite willing to help explaining everything.

Don't imagine that parts from Atlas will be cheap!

Oil and Filters $500+ every year to maintain the warranty. Then add the belt, thermostat, and drain if it has the chiller. There's another $500 every other year.

$200+ for a "unloader pipe upgrade" for mine, it was 2 pushlock fittings and a piece of hose. Would have been about $20 from McMaster...

Jaxian said:

Thanks for the recommendations guys. So like they said it wants to be run constantly. So this should work out well.

Click to expand...

as long as you don't "short trip"( car analogy ) you are good. my 15 hp kaeser rorary runs 1 hour on 1 hour off. i have a lot of storage. stay away from vfd driven, keep in contactors or off the shelf soft starts. you just want to keep the water burned out of the oil. running even a 5hp 100% is a waste. an on/off pressure switch rotary with a 400 gallon tank should suit you well. in the end buy quality you won't regret. Its like buying a peterbilt instead of navistar, those that work on them know the difference.

We got a 5hp IR Screw for virtually free this past year, its delightfully quiet. No problem having a conversation on the phone next to it while its running at 150psi. Don't think I'd spend new money on an IR though.

2hp HV02 hydro-vane will do that comfortably and you can hold a conversation beside it. leave the piston compressor there to meat aditional demands - back up. HV02 is sub £2K over here and there good for 100,000 hours so long as you do the regular 2K hour services.

Well because everyone said I should at least get a price on a Kaesar I went ahead did that.

First I check the internet. No prices available anywhere. Annoying but no big deal. I called the first Kaesar place that came up on Google. They said they can't give me a price I am not in their area. So then I Googled looking for the local dealer, found them and gave them a call. Nice lady answered and said she couldn't give me a price but she could give me the cell phone number of the guy who could. Called him and it took about ten minutes but he was able to find a price.

Have to admit, compared to the Atlas/Copco people who were calling me back with information I wanted. Picked up immediately when I called. Answered all my endless questions without getting annoyed or immediately connected me with someone who could answer if they couldn't. Walked me though the website so I picked the right items. Helped me find some accessories I wanted and just generally had some of the best support I have seen in a while. All this and I hadn't even bought anything yet. Very impressed with that I have to admit.

So hoping the quality is good enough for my needs. Some of the comments here have me worried.

Final tally for those who want to know. On comparable units 5hp/60gal/dryer/3phase

Kaesar was all in with shipping etc at about $8500. Just remembered that since the local dealer is in CA to add tax. $9265 total.

Atlas/Copco with same features and stuff was $5900 (actually I added a lift gate since no forklift so add $75 so call it $6000)

I am sure the Kaesar are awesome but I can't justify a 50%+ price delta right now. Yes if it turns out to be unreliable junk you guys can say I told you so .

I beat the hell out of a 5hp single stage twin for about a year when I got my first VMC. I was at about a 50% duty cycle on it. I had to replace the on/off pressure switch twice during that time and finally saved up enough and got tired of listening the clatter in the back of the shop. I replaced it with an Atlas Copco GX4FF which has a 60 gallon tank and the refrigerated drier and timed auto condensate drain. Sounds like the same size as the one you are looking into. It has been one of the best investments in terms of shop environment quality improvement. You can stand next to the compressor while its running and have a normal conversation.

The only trouble I ever had with it was a thermostatic valve go out at 2500 hours which I replaced myself for 300 bucks with help over the phone from my Atlas distributor Air Technologies, and finally I have had 2 different times developed pin hole oil leak in the metal casing of the air/oil separator (approx $60 bucks) several hundred hours from new filter change. I think it was a manufacturing defect in the metal stamping of the case. I know its alot of money for a small shop, but I don't think you will regret it. I never have capacity issues with guys sand blasting running air tools or painting. Clean dry air in limitless supply.

if it were my dime, I would have a separate dryer. All the big boys have a cooling loop- usually recomended 20-50 feet of pipe between compressor and big honking water filter, then the dryer. Let ambient cooling do some of the work, take some load off your dryer. I like the dryer to be able to be replaced separately... one of my issues with the all in one units. but to each their own. If it were me I would likely throw a big tank inline with the compressor I have now and see how it goes.... if you can extend the off/ run times with tank thats your cheapest route most likely. Run your piston compressor until its dead while you figure your next move.

to me it sounds like your power issues are more than the type of compressor. If your electrical won't handle starting current of both at once..... you may wish to speak with an electrician before you blow your wad and not fix your real issue,,, crashing the cnc when the compressor draw spikes.

If it were me, I would start by putting a muffler on the existing compressor intake - most of the noise usually comes from the input. I would also add an extra storage tank. Tanks are pretty cheap and so are mufflers. It would not cost much and might make the existing setup more reasonable. edit - added muffler link

Vertical Air Tanks – Compressor Air Receiver Tanks | Compressor World

Search results for: 'muffler'

https://www.grainger.com/category/intake-filters-and-silencers/air-compressor-accessories/pneumatics/ecatalog/N-kjt

You are right on WillieO6709. I talked with the guy at Atlas/Copco about some of the stuff brought up here and if there was going to be any issue with moisture. I have never had any before.

He recommended that if I had concerns to go with the non dryer unit for much less money and if I need to put the stand alone dryer at the last point before the VMC. There is about 85' of pipe from the compressor to the VMC pick off point. I have never had air in the system so he said, save money and put in the dryer only if it is an issue. Never had someone talk me out of the more expensive unit but I will try it.

Sounds like from your description that will work better when implemented anyway.

As to the power. Again you are right. I am on a RPC that is handling the load but my transformer on the pole is ancient. Allows large voltage fluctuations. I submitted an application to Pacific Gas & Electric for a 400 amp 3 phase upgrade on 3/19/17. They said they will be able to let me know...in November. Yes, 8 months for them to get around to giving me a price and whether they feel like doing it. They have been a nightmare. Running a patchwork electrical setup for now. Have jobs starting to come so can't wait for them anymore. Thanks for the help guys.

A few thoughts..

Bigger issue, the voltage surges are also messing with the VMC when it kicks on.

Click to expand...

Do you have an unloader valve issue? or is your one way valve going into the tank messed up?
If you are trying to start the motor with the cylinder(s) already pressurized you're going to
get a hell of a spike.

You could try a slightly bigger pulley on the motor, slowing down the compressor a bit might make it
quieter also.

Don't they make gizmos that will soft start the motor.. Kind of like your spindle motor, it doesn't
go ON/OFF, there is a ramp time in there that can be set.. When I was running my big lathe on a
phase converter, I had to go to a 5second ramp to keep the machine from shutting down.


Air curtain? From what I could find.. Pressurized spindle???

That's a TON of wasted air.. That has to cost... Wonder if you could regulate it down?
Its just to keep coolant and shit from getting into the spindle isn't it?

This is the single (there is never a single issue) reason I dumped a brand new Horizontal. It used 21 cfm of air. I just could not stand listening to it by pass air. I went with a different brand of screw compressor that was a oil barfing nightmare (cant think of it now..ebay..)

I ended up with this V4 piston 7.5hp 8gal Horizontal Compressor | Polar Air by Eaton Compressor
It is a air monster and you can just buy direct. There is plumbing on it to flip a valve and it will run continuous to eliminate the on and off.
Also I would vote for more air tanks they are cheap, large piping and a series of tanks help with water also.
Gary

I'm running a 7.5 Polar Air Screw-type, with Vari-drive. Works awesome. Had been running a 5hp piston. Electrical bill did not increase. 5 mills, 2 lathes. Sorry, don't remember all the individual air requirements. I did buy the version with a 120 gallon tank. The noise reduction from the recip is fantastic.

Jaxian said:

Thanks for the recommendations guys. So like they said it wants to be run constantly. So this should work out well.

Interesting the quality comment. Usually people only recommend the Kaesar, Atlas/Copco or Quincy (who are a division of Atlas/Copco).

Click to expand...

Do they make a Sullair as small as you need ? We were very happy with the made-in-China one we had. (Don't know if it was licensed or actually made by Sullair.) One made in the US should be better ? And I'm pretty sure it was less than what you've been quoted. Wasn't quiet enough for phone conversations next to it, but wasn't real annoying either.

WILLEO6709 said:

if it were my dime, I would have a separate dryer. All the big boys have a cooling loop- usually recomended 20-50 feet of pipe between compressor and big honking water filter, then the dryer. Let ambient cooling do some of the work, take some load off your dryer. I like the dryer to be able to be replaced separately... one of my issues with the all in one units. but to each their own. If it were me I would likely throw a big tank inline with the compressor I have now and see how it goes....

Click to expand...

Yeah about the big tank but I looked into the dryer thing pretty thorughly when I had to replumb our shop. Chinese guys, forget it.

Refrigerating driers work best when they take the hottest air possible and cool it the most. Originally our losers put the drier after the receiver which was a disaster. Putting it as close to the compressor as possible, giving it the hottest air possible, and chilling it the hardest gave us the driest air. Cost more electricity and was harder on the chiller but too bad, that's what its job was - to dry the air, not take a nap.

We have extremely high humidity here tho, so you may not have to go to that extreme.

BobW: Yeah the first easy change was going to be to hack in a VFD to soft start the compressor so it ramped up to speed (going to have to do that to the Through Spindle Coolant pump too, it spikes hard and crashes the machine, never been able to run it). That would take care of the spike. Only thing was it's still deafening while running and it would still cycle a lot and put a lot of stress on the (not sure if this is the right name) starter contacts.

And yeah, the Air Curtain is just what you said. It pressurizes the spindle bearing area outside of the spindle tube with 18psi at about 4 cfm. This is to lube the spindle bearings and also keep mist out of there. Apparently very common and makes for greatly reduced bearing maintenance and failures. But even at low pressure, it is just a few psi above outside pressure and you can barely feel the air come out, but it hisses and kicks out a ton of air by volume.

SeaMoss: So your vote is Dryer close to the pump as possible. I really have a chance to put things wherever I want at this point so will gather everyone experiences. As of now with the present setup and the big piston compressor I have never had any water in the lines ever. In the tank drain yes, but at the first water separator which is about 40' of line away never seen anything. Never anything at the two next pick points each 30' apart. Last one is the one the VMC gets air from, goes another 25' through a hose. That shop area is temp controlled so never very high humidity.

In talking with the guy at Atlas/Copco we set it up so that I could grow the system depending on how things react to the new rotary compressor. Since I had no experience with how they work for me we made it so I could add tanks or dryers or other things and not get locked into it up front if I don't need it. Have to say again their tech sales guys were great. Hoping the unit is made well as I like dealing with them.

Your electric company SUCKS!!! The few times I've inquired about 3 phase, the engineer was out here
with in a week, and had a quote shortly after that.. When it actually went in, they did it for free
due to the electricity usage, around $800 a month.. Of course half of that was the F'n phase
converters, so it dropped down to around $400 or so.

On your side of things.. Sounds like something is wrong there also.. Just a few thoughts...
Do you have adequate wire size? Are you running aluminum wire? even if you aren't, I'd go
through and make sure all the connections in all of your boxes are tight and check for corrosion..
And pull the breakers and check that.. Maybe even go so far as to put new breakers on your machine
and compressor, you can't see burned contacts and/or corrosion inside of them...

Maybe get somebody a little tipsy and have them drive into your electrical pole, smash the transformer,
or maybe some target practice..

8 months just to get an answer on 3 phase is Bull SHIT... I would be on the phone bitching every day.

Running on phase converters and not having enough juice sucks... 3 phase day was absolutely fantastic..
I actually to run the big lathe in high gear for the first time...

3 transformers on the ground... 3!!!! Count 'em.. That was a great day.