IR screw compressor or Quincy piston?

[Edster]

I need a new compressor in the shop. I would like the best air quality I can get. I have a few air/oil spindles on my cnc's that I don't want to pump low quality compressed air through.

Right now I have a 1984 Champion 3hp compressor, all cast iron with disk valves (no reeds). The compressor works great and was keeping up fine until I got my new Okuma, so I need to upgrade before I burn this little guy out. I plan to retire it to my garage

I have it narrowed down to a IR UP series 15 HP total air system (dryer and filters), or a quincy piston compressor with a separate dryer.

I like the quiet operation of the IR, but are they as dependable as the quincy? For the price of the IR I can get a nice quincy that I know will last 20++ years. Considering my Champion is 20+ years and going strong I would like the new compressor to last 20 years too.

Is the air quality of the quicy with a dryer equal to the IR screw compressor?

Thanks,
Ed

 

[J Henricksen]

The maintenance costs - oil and air filters for the I-R are going to be higher than a piston Quincy. If you don't need the constant high cfm, I would lean towards the quincy. The air quality will be similar between the two- properly filtered regulated air etc. I like Worthingtons and Atlas Copco rotary vane units. They don't require the real special oils and are quite cheap to maintain and repair compared to a rotary screw.

 

[AlleyCat]

Ed- I can't comment on the IR or Quincy compressors since I never owned one of them. But I did have a Joy 15 Hp rotary screw compressor that we ran for over ten years with zero problems. I think the model number was TA-015 or something like that.

We made sure the oil level was correct and changed it several times during that ten years. That compressor was not any quieter than a piston type but it was a different type of noise. I don't know if screw compressors are the best but that Joy compressor never failed and was very reliable.

We also had a small scroll compressor with a built in refrigerated air dryer. It was about 5 HP and was used with a Mitsubishi CNC Laser cutter. That compressor was so quiet that when other machinery was running you couldn't even hear it. Sometimes I had to look at the power light on that thing to make sure it was on. It wasn't much louder than a refrigerator. I wish I had one of those in my home shop right now.

 

[WILLEO6709]

I started in rotary compressors with a used joy twistair 20 HP. I have no idea how many hours it had when we got it, but we put 50-60k hours on it before it died completely. Now I run between 2 ingersolls. 1 is a 25HP with about 38k hours, the other is a 60HP with aver 100k hours. I run the 60 when blasting so the rest of the shop maintains air pressure. Either will probably do you fine, but the ingersoll screws are a very good compressor with good reliability.

 

[JL Sargent]

Cost per CF of compressed air should be much lower with a screw. Do you need 15hp worth of air? Seems like IR makes screws down to about 7.5hp. Recip is great for the low volume user, but the screw is king of the hill.

 

[Timw]

I've worked on a lot of compressors, almost all piston, a couple diaphragm. But No screw comp. Almost all of their problems were neglect or abuse. It would seem to me that a major problem with a screw comp would be major cost to repair.
The majority of problems with piston comp can be repaired in the top end. Not a lot of high cost here. The bottom end lasts with good oil monitoring and service. Another plus for piston is a two stage unit and 175psi. I don't think that is posible with screw.
As for quality of air that is controled after the unit depending on how much you want to spend.

 

[John Garner]

Why are you choosing between one type of compressor made by one company and another type of compressor made by another company?

All three of the companies you mention -- Champion (now a subsidiary of Gardner-Denver), IR, and Quincy -- offer both reciprocating and rotary screw compressors.

Me? I'd hesitate to buy an IR, because for probably twenty years now I've been hearing stories of major problems with new IR compressors from people I respect.

 

[dkmc]

For added up front cost, you can get screw compressors that are variable speed and can save
on electrical costs over their life span.
They run only fast enough to supply as much air as needed.
Piston compressors are ok, except half the time they're running the pistons are going in the wrong direction.....sucking air in instead of blowing it out....

4 ways compressors are abused:

1. Compressors don't use oil, so don't bother checking it.

2. Compressors aren't like 'engines'....the oil never gets dirty ....so why change it?

3. It's out in the shed (upstairs, in the basement,etc) ....and it makes 'normal pumping sounds' when I turn it on, so it doesn't need maintenance.

4. I did the service on it ....last summer....I think... (actually 6 years ago).

dk

 

[LD]

The IR screw will provide you with continuous smooth air (no pulsations like a piston) at about half the temperatures. There are no change-of-direction cycles with a screw so no high stressed crank and bearing journals.

This relates to clean, relatively low moisture air that you could pump continuously if you had to.

Benefits to you depend on your application.

Race cars put pistons in the bottom end to take advantage of the change-of-motion, and screws on top to take advantage of cool, smooth air, and lots of it. (I know, there's little relation here, but I couldn't stop my brain and finger inter-connection).

 

[mobile_bob]

having worked for a company with a 50 hp screw compressor that had in excess of 60k hours i became concerned about whether or not it should be rebearinged, i call the manufacture (the name escapes me just now) their responce

"why do you think it needs overhauled?"

i said, because it has 60k hours on it, and am worried about it going down.

"well, stop worrying,, we routinely get well over 120k hours before we even think about new brgs and seals, provided the oil and filters are changed per recommendations"

it used standard atf dexron 2 and i am sure that thing is still pumping air like a mad man, it also had a throttleing device that tapered back the air so that it needed no storage tank.

for my money it would be a no brainer, if i could afford a screw compressor that is the one i would go with.

that machine took 5 gallons of atf and a ph8a filter running 24/5 and 8 to 12 hours on saturdays, got an oil change about once every 60 days if i recall.

bob g

 

[dirty old man]

I'm wondering about the need to jump from 3 hp to 15 in one fell swoop! Are you adding in excess capacity in hopes of meeting future projected needs or what?
I seem to remember reading somewhere that screw compressors don,t take too well to start/stop situations where pumping capacity is greatly in excess of needs.
Dave

 

[precisionworks]

but are they as dependable as the quincy

At least a dozen times more so. We run a 300 HP, two 100 HP & two 75 HP screws. Change oil every 8000 hours, make sure the air intake filters are clean, end of story

--------------
Barry Milton

 

[Edster]

Thanks for all the replies!

My old compressor was keeping up except for the occasional high demand of some air tools. Until the new Okuma showed up. This thing uses a ton of air. I'll bet my Champion 3hp is at 75-80% duty cycle just when the spindle is turning on the Okuma. I haven't even turned on the air blast. The screw compressors seem like the way to go and the price difference between the IR 7.5 and 15 hp isn't much. Above 15hp the price really starts to jump. Considering the compressors are the exact same size I'll take the 15hp. I figured in a few more years and a couple more machines the extra capacity will be welcome.

The IR screws that I'm looking at come in three flavors. 125 psi, 150 psi, and 210 psi. I'm leaning toward the 150 psi. So that negates any advantage of 175psi on the quincy.

What is an atlas copo rotary vane unit? Is that the one that is rebaded as the Chicago Pnuematic. I even saw a small rotary screw on the quincy website that looked like the atlas copo compressor.

 

[Edster]

Why are you choosing between one type of compressor made by one company and another type of compressor made by another company?

I'm really looking for a "total air system" I've looked at the Chicago Pnuematic rotary screws. I don't like how the refrigerated dryer is like an afterthought. I like how the IR has the dryer before the tank, and it also cycles on and off with the compressor. The IR also has filters. I also looked at the champion screws. I didn't find any packaged systems just the components. The smaller quincy screws look like the atlas copo units that are rebaged just like the CP's. I looked at Kaeser too, but for the price I can buy two IR's and I really don't think I need a computer to control the air compressor

seems like a bit of overkill.

I'm considering a quincy piston compressor because the price is in line with the IR screw and they have a great reputation for reliabilty.

For added up front cost, you can get screw compressors that are variable speed and can save
on electrical costs over their life span.

I'd love to get one of these units, but I'm afraid to price them.

 

[surplusjohn]

don't forget your demand cycle, the extra electric a compressor uses occasionally can really bump up your electric bill. If you have spikes in your air usage, it is probably a better idea to use a smaller compressor with a larger tank to advoid the electric useage spike.

 

[Richard Rogers]

J Henricksen,

I had a 40 HP Worthington I sandblasted with years ago. It was a rotary vane compressor, and it worked fine. It was a bit large for me, and I sold it.

Any idea why the vane types aren't more prevalent?

Richard

 

[JL Sargent]

Hey RR, I think its just economics. A 30hp two stage screw can probably out do a 40hp rotary vane on 120 psi output. I do remember my experience with the rotary vanes being they were very reliable.

 

[precisionworks]

Any idea why the vane types aren't more prevalent?

A short explanation of rotary screws, click here.

And for rotary vanes, click here.

Most rotary vanes that I've seen are smaller units, some are tabletop size. Often used to generate a vacuum in a lab or for a process control. There are larger ones that are diesel or gasoline engine powered.

-----------------
Barry Milton

 

[Tom1]

back in the 1990's I sold IR compressors. Models and quality have changed ALOT since them, but. Screws should be sized to run about 75 to 100 percent of the rated capacity. Screws, you turn it on in the morning, the motor runs all day till you turn it off. You dont want to cycle a screw with a pressure switch. The piston machine will run on a pressure switch or if your load gets higher you can run the machine with the un loader. this is where the compressor runs and just makes pressure as needed, this is done by opening and closing the valves in the cylinder head.

As far as air tank size (receiver) if you have an even load all day with out spikes, a small tank is all that you need, even no tank is ok. If you have big spikes then you need a larger tank sized to your spike loads. Most people by to large of a tank. After coolers, if its mounted on the compressor, its an inter cooler, this allows you to plumb the after cooler closer. With out an inter cooler, you need 15 to 20 feet of pipe from the compressor to the after cooler. You will not get drier air from one type of compressor to another, moisture is a function of heat and due point. As for service, piston machines need oil changes, if you run them hard they need valve jobs. Screws do need at least annual oil and oil separator changes, today you run a full synthetic oil, its expensive but worth it, there is a lot more to go wrong on a screw, from solenoids, dampers, ect.

If it were me, Id buy a 10 HP Quincy and keep the old 3 hooked up as a back up or for low use days.

Also if you look at brands of compressors look at CFM not horsepower and look at pump speed, slower is better.

I am not a big fan of belt driven screw compressors, direct drive is better

 

[Tobias-B]

Screw compressors do howl, though...
only a concern if you're living with it.

t