Rebuilding an Atlas Copco Compressor

[Lonstar]

Looking for advice on rebuilding an Atlas Copco LE7-UV compressor. I got this for the motor that was attached to it, turns out the motor was bad. Exploring what it would take to rebuild the compressor.

Back story is the guy bought 2 of these at a government surplus auction. They had 3 phase motors on them, he and his brother bought 7.5 hp single phase motors for them. This one ran for about 1.5 years and then the motor started smoking. He thought smoke was from compressor and motor was still good. I found it was the motor that was smoking.

Don't know anything about rebuilding a compressor but have mechanical background and tools...just need help on proper way to do it. I know it won't be cheap, hoping to find someone that has experience with this model that can help. Found very little info online, but did find a website (I think on Atlas Copco website) that offered a rebuild kit for $500. Don't know if that was for a complete rebuild, pics showed gaskets, o-rings, etc for the heads.
Any help would be greatly appreciated.

 

[American Locomotive]

If the motor failed, why do you need to rebuild the compressor? Most compressors are generally pretty durable.

It would not be worth rebuilding that compressor if the rebuild kit is $500.

Also, do you have the fan shrouds?

 

[scooby074]

28 CFM ?. A decent pump plus Atlas Copco is a top brand, Id keep it. Are you sure the pump is bad? I wouldnt just rebuild it for shits and giggles. Thats a "20,000 hour", industrial oil lubed compressor. https://www.atlascopco.com/en-ca/co...-industrial-oil-lubricated-piston-compressors

Lots of Copco dealers out there, call around and see whats available for a kit/parts. Like an air cooled engine that pump will get pretty hot without the shrouds. That fan wont pull anything over the fins. Without the shrouds (or the ability to make them) that could change the viability of the machine.

Bare pump is worth about $2000 new. http://oemaircompressor.com/AtlasCopco-8115460019.aspx

$400 kit https://compressedairpartscompany.com/1503-6140-60replacementatlascopcokitsparepartlelt.aspx

 

[930dreamer]

Find another motor cheap and bolt it on.

 

[FSrepair&fabrication]

Find another motor cheap and bolt it on.

^ Youre gonna need a motor to test the pump first. Id hook it up temporarily and see how fast it pumps up. That is a high quality pump motor. Id be surprised if its worn out.

 

[Lonstar]

Yes, I have the shroud, took it off to get a better look at the innerworkings.

Why rebuild? Mainly because I don't what's wrong with it and don't want to risk possible further damage. What caused the motor to overheat and melt the windings after 18 months? It turns over by hand and puffs air out exit pipe, so that's a good sign.

Was looking for a 7.5 hp motor for another compressor I have when I came across this on craigslist. Extremely lucky timing - the ad was 9 minutes old, price was "free", and it was 2 miles away. I was there within 30 minutes, ad was 45 minutes old, guy said he had at least 8 calls already. Most were scrappers asking how much it weighed.

The guy makes metal parts. His small shop consisted of all the machinery necessary to cut, grind and drill metal, and a large CNC machine. Works by himself and seemed very busy. Went next door to borrow a forklift, shucked it in the back of my SUV and that was that. Tried to call him a few times to ask questions but went right to VM. Finally got ahold of him, he was hurried, answered questions with few words. He was nice about it but I detected a "you got it for free, I don't have time for this" attitude.

Here's what little I got out of him other than what I already stated. At Gov auction, compressors were stored outside with a tarp over them, looked like they'd been there for a long time. His compressor ran ok, but not as good as the one his brother had. He didn't elaborate on that. Said he had just changed the oil, fired it up and the "compressor" began to smoke. That's when he said "it just never ran as well as my brother's did". He honestly thought the motor was still good and the compressor was the problem. I disconnected the motor (direct drive to compressor), clamped it to the bench and used a 40a oven cord to power it. Already noticed the windings were black in one spot so didn't have high hopes. Plugged it in, motor spun up and started smoking immediately.

I'm thinking if I can rebuild it for around $500, might take a chance. But I don't know anything about the insides of a compressor and from what I've found so far, will only have parts diagrams to guide me on how it comes apart and goes back together. I'd like to have more than that if possible. Would be great to know torque settings. I ended up buying a new 7.5 hp motor for the other compressor, I could use that to run this one once rebuilt.

Really not sure what to do.

 

[Packard V8]

One possibility; since the label indicates that's a 125 PSI max pump, which is a high-volume-low pressure model. It's possible it was being over-driven to produce the typical 150 -175 PSI of a two-stage pump. That will overtax both the motor and the pump.

When sizing the motor pulley and the pressure switch, make sure their setting match the design of the pump.

jack vines

jack vines

 

[FSrepair&fabrication]

If this pump was designed for 3phase and its being run with a large single phase motor im not surprised the motor wore out. 3phase makes more torque and is more balanced so less vibration, both of which will kill that 240 motor in short order. maybe you could use pulleys and a belt to gain some mechanical advantage with single phase.

Also, check the oil in the pump, it will tell you alot, but i doubt the pump is that bad off since that little single phase motor cant push it very hard compared to what should be powering it. Especially if its pressure lubricated, low rpm on a splash lubed compressor is bad, but pressure lubed will be perfectly fine if its full on oil.

 

[American Locomotive]

HP is HP. 3 phase motors only have more startup torque. A 5 HP 1800 RPM 3 phase motor will make the same operating torque as a 5 HP 1800 RPM single phase. At near 20 CFM, that compressor will indeed need an 1800 RPM 7.5 HP motor.

As far as rebuilding goes I'd try and run it before anything. If the motor had proper overload protection, you shouldn't be able to hurt it with an overload. Sometimes motors just burn out.

 

[Packard V8]

HP is HP. 3 phase motors only have more startup torque. A 5 HP 1800 RPM 3 phase motor will make the same operating torque as a 5 HP 1800 RPM single phase.

Agree; the following caveat will not be news to most here.

Except when it's big box store compressor horsepower. Sad note but most all the major US industrial air compressor manufacturers have whored out their name to cheap Chicom junk being stacked at the entrance to Home Depot, et al.

The horsepower ratings on consumer grade air compressor motors are a sad lie. If actually forced to develop the rated horsepower continuously, those little sheet metal framed poseurs will soon emit the magic smoke.

If one installed a 5hp or 7.5hp box store motor on that Atlas Copco in commercial service, it wouldn't last a day. Maybe it's as simple as that.

jack vines

 

[930dreamer]

If just the motor smoked, no reason the touch the pump. You could test with a 5 hp motor and see how it operates.

 

[FSrepair&fabrication]

I know alot of self certified electricians want to say that there is no difference between 3 phase and single phase, but if that were the case no one would be using 3ph. And if single ph was good enough why didnt atlas copco spec that pump to be ran by a single phase motor? I think the original problem was that the seller thought the same thing and used an inadequate choice of motor to drive the pump thus burning it up. The fact that he couldnt tell the difference between the motor being bad and the pump tells me he shouldnt have been redesigning the type of motor it uses either. 3ph = less heat, vibration, more consistent torque output, blah blah blah. If anyone disagrees go read a book, and learn what youre missing. Maybe it will run on single phase, but how reliably or for how long is a gamble.

 

[Packard V8]

FWIW, most compressor pumps are not specified as to phase of motor, only horsepower required and RPM. Up to about 10hp, the same industrial pump is delivered powered by either a single phase or three phase, buyers choice.

Yes, there are reasons industry runs three phase; motors are less expensive to build to a given horsepower, more durable, less expensive to operate, and yes, more consistent torque output.

No, there's no reason that Atlas Copco can't be driven by the correct single phase motor.

jack vines

 

[Lonstar]

Well (unfortunately?) the motor wasn't a Chicom poseur...enjoyed that, thanks for the laugh! It had a real deal, 110 lb, 36 amp Leeson on it. Compressor tag states 1800 rpm, motor is 1740 rpm. No pulleys with this, it connects directly to the pump 1:1.

Can't easily put a 5 hp on it to test. The frame the motor bolts to is sized for a 215T motor to line up directly with the shaft on the pump. Could Chicom-rig something (sorry, couldn't resist) to bolt motor on and at correct height, but would have to buy a reducing flex coupler to go from 1 3/8" shaft (215T) to 7/8" shaft (56Y). I imagine that wouldn't cheap, at least not for just a test.

Like I said, just bought a 7.5 Baldor for the other compressor I'm working on, it'll be delivered tomorrow. I could mount it on the Atlas and clamp an amp meter on it to see what it does. I guess it's the least I can do. Would also have to dig out that old Craftsman oil-less compressor I stopped using some time ago and rig that tank to it.

Attached pics are of the tag on the Leeson motor that was on the Atlas when I got it, a pic of the Leeson motor next to a 5 hp motor, and the 5 hp motor on the motor mount of the Atlas.

 

[MacMcMacmac]

Really not sure what to do.

I'd sell it and buy something more practical.

You could probably pocket a few hundred for it. It's probably a pretty annoying piece of machinery to have to work around at 1800rpm. I would not want to have to replace any hard parts on a Copco recip. I have worked on exactly one in 25 years. Like most Euro machinery, it seems to be chock full of weird castings and metric fasteners unlikely to be available at any repair depot near you, as least in a timely manner.

Pulling steel fasteners from aluminum that were torqued into place in 1993 might be an interesting experience, especially if they were exposed to the elements.

Copco parts are $$$$$. I changed out the desiccant in our instrument air dryers a couple of years ago. Instead of tanks filled with desiccant, they had ABS plastic containers in them with mesh screens and fabric filters pads, filled with desiccant, spring loaded in place, all glued together. $2500 apiece to replace. It would have been near $20000 to do all of our machines for a simple desiccant change. I cut them apart, made up some new steel caps and filled them up and replaced them for under $1000. The spring loaded caps and screens allowed the dryers to be mounted in any position, but that was an option we did not need.

 

[marinusdees]

A real 5 or 7 1/2 hp motor has a 1 1/8" shaft. That coupling on the end of the compressor is a "Lovejoy" and you should have the motor end and the spider if they were coupled when you got it. You should be able to adjust shaft height and size (use/make a bushing) well enough to test run. You have the pump, the motor and time.
My first compressor was a v-6 Dunham-Bush refrigeration compressor (free) driven by a 5 hp GE Triclad directly thru a Lovejoy. Free off a friend's **** pump (a dairy farmer). I had to buy the Lovejoy, not cheap. No unusual noise or vibration. Home made sure. 40 years old, sure. Sold to a friend of my son's for $300. I could sell the Triclad for $300 today. It is still running. If you have both sides and the spider for the Lovejoy, the rest is just geometry. You are spared the nuisance of calculating pulley sizes. The Lovejoy is the expensive part, and, you should have it.
I'd welcome the challenge of this project, but I am not under any time constraint. If you are not in a hurry, do it. Do I think it will work?? Absolutely. Do I think this compressor will do what you/need want it to do?? I don't know.
The Lovejoy is designed to compensate for minor alignment discrepancies and will minimize noise. 7 1/2 hp is 7 1/2 hp. hp doesn't know the difference between 3 phase and single phase. If you build it with a pressure unloading start switch, as you should, the problem of starting torque being insufficient is obviated. I think if 7 1/2 hp is sufficient, and you allow it to start without any pressure on the head, it should work fine.

Jus' sayin'.
PS I know and understand the 3 phase versus 1 phase factors. This post is not to start an argument about the relative merits of each. It is to address the feasibility of this exercise.

 

[American Locomotive]

I know alot of self certified electricians want to say that there is no difference between 3 phase and single phase, but if that were the case no one would be using 3ph. And if single ph was good enough why didnt atlas copco spec that pump to be ran by a single phase motor?

That compressor had a 3 phase motor on it because it was sold to an industrial customer. 3 Phase power is readily available for industrial customers, allows for more efficient motors, higher starting torque, simpler & cheaper motors, and reduced wire size.

When you buy a compressor pump, they don't specify whether or not it needs a single or three phase motor. They specify an RPM and a horsepower to spin it. Almost every manufacturer will sell you single or three phase versions of the same air compressor up to around 7.5HP or so.

Maybe it will run on single phase, but how reliably or for how long is a gamble.

It's not a gamble. The compressor pump will not care. It's a reciprocating compressor - not a 120,000 RPM 4 stage centrifugal compressor.

 

[FSrepair&fabrication]

Absolutely right the pump will not care, it is the motor that will be the weak link, I thought that was kinda obvious. Its like buying a diesel truck and putting a v6 gas motor in it. Sure, it might work but not how it was intended to be.

 

[KamiCrit]

So your induction motor smokes. If the reality is the windings are shot/shorting, all the OEM rebuild kits on the claim won't help yeah out.

The motor shaft spins easily by hand right? Not dealing with rusty shot bearings from the camping trip outside?

Smoke and ugly windings on the inside, I'd test the windings with a multimeter. Make like an industrial electrician and do the usual induction motor troubleshooting song n dance. https://www.electricalengineeringtoolbox.com/2015/12/how-to-test-three-phase-ac-motors.html Single phase should make things 33% simpler.

-Good ground test
-Winding continuity test
-Winding resistance test
-Insulation resistance test (requires a megger, feel free to not blow up the windings on the highest setting.)

Atlas Copco is prolly my fav, but I'm biased as they turn telephone poles of steel into drill pipe just down the street. As others have said, they're the best, and the most expensive. Do the easiest thing first, and straighten out your smoking g̶u̶n̶ electric motor.

 

[WittHay]

Atlas Copco is prolly my fav, but I'm biased as they turn telephone poles of steel into drill pipe just down the street. As others have said, they're the best, and the most expensive. Do the easiest thing first, and straighten out your smoking g̶u̶n̶ electric motor.

Cool, Atlas Copco Thiessen right next to Nahinni. I am partial to Ingersoll-Rand sold by Wiseworth Canada. Used to be in Cloverdale . Some BC "BS"

To the OP, for 7.5hp to work on a direct coupled compressor, you will have to have extra good wiring and make sure the pressure switches or unloaders work correctly. Not as forgiving as having belts and pulleys.

I am familiar with 5 hp TEFC farm duty motors. Most are 184 and are on belt driven equipment. Even with 5 hp you need time delay fuses if you have switched fuse boxes and will dim the lights on anything below a 200 amp service on start up

I think a 3-phase motor for this particular compressor is better, mainly for starting, not so much for actually running it

 

[Lonstar]

I'd sell it and buy something more practical.

It's probably a pretty annoying piece of machinery to have to work around at 1800rpm.

Pulling steel fasteners from aluminum that were torqued into place in 1993 might be an interesting experience, especially if they were exposed to the elements.

Selling it has crossed my mind, but probably won't have much interest if just the pump. If selling as a running compressor with motor and tank I could probably make a few bucks. Steel stuck in aluminum didn't occur to me, good point. Aerokroil can't fix everything.

A real 5 or 7 1/2 hp motor has a 1 1/8" shaft. That coupling on the end of the compressor is a "Lovejoy" and you should have the motor end and the spider if they were coupled when you got it. You should be able to adjust shaft height and size (use/make a bushing) well enough to test run.

If you build it with a pressure unloading start switch, as you should, the problem of starting torque being insufficient is obviated. I think if 7 1/2 hp is sufficient, and you allow it to start without any pressure on the head, it should work fine.

I've done my homework on motors. A 5 hp motor with a R56Y frame has a 7/8" shaft. 7.5 hp motors with a 182T/184T/187T frame have a 1 1/8 shaft and shaft height is 4.5".
7.5 hp motors with a 215T frame have a 1 3/8" shaft and a shaft height of 5.5". The pump has a 1 3/8" shaft. It connects to the motor with a TB Woods Sure-Flex Plus coupling, and the flanges on both sides are 1 3/8". Flanges are about $45 each, would need to buy one if using a motor with a smaller shaft.
When looking at the pump from the front (shroud), on the lower right side is a square shaped part with cooling fins and a filter. That's the unloader valve. Don't know how it's triggered, maybe it automatically unloads when the compressor stops? Obviously it's separate from the pressure switch on the tank.

So your induction motor smokes. If the reality is the windings are shot/shorting, all the OEM rebuild kits on the claim won't help yeah out.

The motor shaft spins easily by hand right? Not dealing with rusty shot bearings from the camping trip outside?

Smoke and
-Good ground test
-Winding continuity test
-Winding resistance test
-Insulation resistance test (requires a megger, feel free to not blow up the windings on the highest setting.)

Do the easiest thing first, and straighten out your smoking g̶u̶n̶ electric motor.

Yes, pump spins fairly easily by hand. I took the motor apart, one section of the windings are black. The wrapping and winding ties on that section are burnt away, what's left is brittle and easily breaks off when touched. Didn't bother to troubleshoot anymore when I found that.

To the OP, for 7.5hp to work on a direct coupled compressor, you will have to have extra good wiring and make sure the pressure switches or unloaders work correctly. Not as forgiving as having belts and pulleys.

I am familiar with 5 hp TEFC farm duty motors. Most are 184 and are on belt driven equipment. Even with 5 hp you need time delay fuses if you have switched fuse boxes and will dim the lights on anything below a 200 amp service on start up

I have 100 amp service in the garage. If I use this compressor I would put a mag start on it and wire it with 6 gauge copper. That should fit the bill, shouldn't it? Can't imagine needing 200 amp service for a motor with a max service factor rating of 40 amps.

 

[FSrepair&fabrication]

Its the initial load to start that ***** the juice and dims the lights. In a single phase motor half of the thing is for starting and the other half is for when its running. A 3 phase motor “fires” every 120* (3 times per revolution)vs single phase which is once per rev. much more powerful starting up from rest. At 100 amps service you should be fine as long as you arent running a welder, AC, lights and whatever all at once. but its still gonna be taxing that single phase motor to fire up. I understand in a home garage nobody has 3 phase, but just being realistic about how it may perform on single phase.

 

[marinusdees]

A real 5 hp motor has a 1 1/8" shaft. Homework or no.

 

[American Locomotive]

A real 5 hp motor has a 1 1/8" shaft. Homework or no.

You can get 5HP motors in 7/8" shaft. Real 5HP, rated at 23A, just like any other 5HP motor. We have 10HP Siemens motors at work with shafts smaller than 3/4”.

 

[marinusdees]

You can get 5HP motors in 7/8" shaft. Real 5HP, rated at 23A, just like any other 5HP motor. We have 10HP Siemens motors at work with shafts smaller than 3/4”.

A REAL 5 hp motor has a 1 1/8" shaft.

 

[American Locomotive]

You're wrong. You can even get 3-phase industrial 5HP motors with a 7/8" shaft.

 

[KamiCrit]

Not sure why we're arguing about shaft sizes, if you flip through any flavour of electric motor catalog (In our case single or three phase AC induction). They'll all love you take your dollar and sell you a motor with a variety of shaft size options.

There is a common size no doubt in the 5HP range, but the catalog isn't lying.

Just takes money.

 

[Lonstar]

Marinusdees - I get it. You're saying a 5 hp motor in a R56Y/182/184 frame with a 7/8 shaft isn't a "real" 5 hp motor. If it's in a 182/184/213/215 frame with a 1 1/8" shaft it is.

Don't understand why shaft size of a 5 hp motor matters in this discussion. I was showing the difference between a R56Y framed motor vs a 215T motor in an earlier post, shouldn't have bothered with that. I only have a 215T 7.5 hp motor with a 1 3/8" shaft, so that's all that really matters (the 5 ho motor I had in the picture is no good, windings are burnt).

The Baldor 7.5 hp motor I bought for the other compressor was delivered yesterday. Hope to have time later today to put it on the Atlas, wire it, ands get a tank plumbed. Amp meter and heat gun readings, and overall sound will tell the tale. I'll let you guys know how I make out.

 

[Lonstar]

Just cut the skid wrap off the motor. It was shipped on a piece of OSB that's a few inches longer and wider than the motor, and wrapped with skid wrap. No bolts holding it in place, just sitting loose on OSB and wrapped with plastic.
The OSB has a 4" wide chunk broken off of it and right above that is a F'ing dent in the motor. It's a 'flat spot' dent in the center section, about 1.5" high top to bottom and 2" wide front to back, right where the body and end cap join. It's not a deep dent, but it's a dent nonetheless.

 

[Lonstar]

Finally had time to give the Atlas a whirl. Bolted the Baldor 7.5 hp motor to the Atlas and used the Mac compressor the Baldor motor was to go on for a tank. The Mac has a nonadjustable Square D 175 psi pressure switch. Although plate on Atlas states 125 psi max, I used it (all I had). First impression - it's quiet. Was expecting it to be really loud, I think it's as quiet or quieter than the 3.5 hp Iron Horse I use now.

Observations:

• Could not find an arrow on the Atlas indicating which direction it should spin. Fins on flywheel are straight, so no indication from that either. Called Atlas, they said if not indicated it can spin either way.

• 
  Tag on motor stated CCW as "STD" rotation, CW as "OPP" rotation, so went with CCW.

• Motor was pulling 33-35 amps (more often 35). Motor rated at 31 amps, SF 1.15, so 35.6 max. Not good. Figured what the heck, see what happens if rotating CW. Amp draw dropped to 30-31 from 0 to 160 psi when running CW.

• Motor speed rating is 1725 rpm, tach read 1768 rpm pretty much consistently.

• As above, tag on Atlas states 125 max psi, pressure switch on Mac is 175 psi. Motor pulled 30-31 amps up to 160 psi, then dropped to 30 and then 29 as psi rose above 160.

• Mac pressure switch must be bad, wouldn't stop at 175. Rose to 190 psi before relief valve on Atlas popped. Did this multiple times to record amp draw and rotation speed. Same result every time, amps dropped as it climbed above 160 psi and rotation stayed consistent at 1768 rpm (I was testing, wanted to see what it would do above spec).

• All observations are from running the compressor 5 times in a row from 0 psi to 190 psi with no breaks in between, other than dumping air from tank through a 3/4" valve. Measured temp with a thermal gun each time. Max was always top of the compressor heads, 185 degrees every time, never hotter.

Now the problem I'm trying to figure out it is how to get the big *** unloader valve to work. I know I need a solenoid or pilot valve, but that's about it. Don't know anything about them or how to wire it. Also don't know if a special type of pressure switch is needed to operate the pilot valve.
Or should I just use a standard pressure valve with an unloader? Really don't want to do the latter because the OEM unloader on the compressor is too cool to bypass. I guess $$$ will rule that decision.

EDIT - Forgot to list fill time!

0 to 100 psi - 2:15
0 to 120 psi - 2:55
0 to 130 psi - 3:20

90 to 120 - 42 secs
90 to 130 - 1:04