Rotary screw compressor recommendation

[drummerdimitri]

I'm looking to buy a rotary screw compressor with a dryer to be used in my workshop. Please don't recommend a piston as they are loud, inefficient and don't come with a dryer built in.

Will be running a CNC plasma cutter (85 A), a blasting cabinet, air tools like a beveller, needle scaler, spray gun, air hammer etc. some of them at once like plasma cutting and the other processes.

Not sure if a variable speed unit would be beneficial in terms of energy cost savings, but I received three quotations and would be grateful if one could help me me decide between them.

The first two are from Atlas Copco (G7 FF and G11 FF) so 10 HP and 15 HP respectively. I'm sure the former would be sufficient for my needs but since the price difference is only 500 $ or so (7,900 $ vs 8,400 $) wouldn't it make sense to get the large unit for futureproofing in case I need to add other air consuming machines?

Lastly, I got a quote for a Champion (part of Gardner Denver group) 10 HP model with inverter and variable speed technology but the price is considerably higher at 10,000 $ which is a bit more than I'd like to pay but if the power savings are substantial, I would possibly consider this unit.

Which of these three options should I go with? I've visited at least 6 different companies locally and after long consideration, I ended up with these three models.

 

[sberry]

This isnt directly about a comp but wouldnt mind hearing about some background on this,,,, fab shop is vague. What type of work, what scale, how many men, whats the budget, what work lined up, is there going to be pressure on the finance for a return, when does it need to profit, what amount of stock, what type/size of buildings.

 

[dnschmidt]

Go to a decent sized body shop (10-15 car capacity) and see what they're doing. Your air needs should be about in line with what they have.

 

[drummerdimitri]

This isnt directly about a comp but wouldnt mind hearing about some background on this,,,, fab shop is vague. What type of work, what scale, how many men, whats the budget, what work lined up, is there going to be pressure on the finance for a return, when does it need to profit, what amount of stock, what type/size of buildings.

It will be a one man show (me) for now and there is no pressure on ROI as I am the sole owner of the workshop, have no rental expenses, investors or loans to deal with.

The shop is around 5000 sq-ft divided onto two floors and is my own property.

Will be setting up a workshop for making one off items such as industrial style furniture, design work (company logos, emblems etc.), engineering parts (plasma cut), welding works (MIG and TIG)/repair etc. out of most types of metals.

Basically whatever the customer needs, I'd like to be able to provide with continuous investment from my end depending on how well the business is going.

Would eventually like to dive deeper and get a laser cutting machine, CNC lathe/milling machine, small format metal 3D printer, laser cleaning machine etc.

Hopefully this is enough insight for better evaluating my air requirements.

 

[sberry]

It does help. My shop is 6400 and I have another 10 in storage of sorts. At one time had more men and did paint, some body when I had men but I dont like to sand all that much and never got good enough to be a whiz. Its a job with too many steps for me.
But I have been all the way along the spectrum and have a couple character flaws that prevent me frpom being a good business guy, I get distracted and really more interested in process/production and ergonomic movement than I do in other areas and,,,, its a trade with a pinch of talent I am pretty good at, not a genius but given a chance to do a job twice I am self critical and do it faster or better.
I had a pile of boards to cut up, they needed to be hand loaded in the back of a pickup, backed in to the shop, run thru a saw, stacked on a paltet. None of these guys are dumb but this is a chore. I leave it to the help and I go back and get a coffee and when I come back it looks like everyone is reasonably and have to ask,,, how long at this rate you think this is going to take? Hadnt even considered the thought but it was 2.5 days.
I stoped them for a couple minutes so we move the truck, they were carrying boards all the way around and 1 guy cut at a time, drops the dross on the floor, picke it up and tosses it in a box and they carries the finished product off another 30 ft and it looked like ants. I did the rest of the changes on the fly and had no walking, where one shoved it straight off to the saw that we changed the bench a bit, moved it so the saw was directly over the waste box, didnt have to build anything and by the time we were done had it all swept up in time toi meet the last cut, I was back drinking coffee in 3 hrs and sitting down, got done before the afternoon was out.
Thats my real talent, move all the **** around and do this first now by cord, wheels, pallet jack, pallet boxes I dot 50 of and build stations from all that all the time.
Secondly. Some owners survive it all despite themselves, but they would have exploded if they sougt some help, it ruins the culture, they exhaust the local resource, they can never recover because the talent simpoly will never work there.
Pat is the example of long term right way, I am sure he has seen plenty of ****** production and outright ****** owners. Reason I know this is have done it wrong more than right, sometimes really event, some decent decisions but ****,,,,,,,,,,,,,,,,
I dont some start ups, some bigger and some smaller and a couple still working. Most of the originals are dead or well retired.
I was always better with someone elses money and 1 still in biz used to complain a little when the bills came in realized,,,,, we made money on it. I used rentals a little to prove it out, it gave us a chance to look at other equipment, in other words ,,,, we could do all the work we had to do with a 3K comp and it gave us a chance to look for a deal or prove out, change, sometimes we found it suffecient and still in service 30X years from then because it was all speculative and the demand calc wasnt accurate.
This is where an engineer or a consultant mechanic type may be worth some expense and maybe even make money on is to focus where the rubber hits the road vs hedges on long term speculation and so easily modified when demand rises and gives some purchace opportunity, you buy a new one and a bid says,,, oh,,, I had one for sale.. no easier way to make money in this business as get deals on machines. It takes a long time for a home hobby welder guy to make 5 grand in a week,,, he can save on setup and ,,,,,,,,,,,,,,,,,,,,,,,, simple basic first leads to so m8uch better design.
I see some workmanship here is fantastic and lots of stuff on it, I understand the hobby aspect but it aint got squat to do with getting work done from the comp. I painted a dozen semis with a hundred foot air hose and a 5 hp compressor.
I can remember it yet, it was in a stall with a door on each end and we moved the comp on the other side of the wall, I put a t in the air line after some filter we found and bout 2 new 100 ft hoses. Had the auto parts deliver one of those 50$ DA sanders and a couple rolls of sanding papers, sleeve of tape roll of paper, and rounded up about 5 box fans and stuck under 1 door and opened the other end man door and it worked pretty good. We demolished it when done, they turned it to something else.
What is relevent about that is I done it a couple times and when I build it in my own I still missed a couple minor things but had some principles better and by the time I finally remodeled it got it right and along the way there was as much simplification as modification or upgrade as actually upgrade and some of it simply moved sideways, some removed cause we were not using it and cheaper to build storage if we couldnt part with it than to keep it in the way.
I tell some masters here, it takes some a little adjustment and I understand how things done other places but this thing we gonna do has almost everything right here we need to do it with.
If a guy has had some mobile, some site, some jobshop and in different trades it can lead to see some of the best actual craft masters with simple tooling limited to a 5 gallon pail. I can get involved with creep and I had 5 wrenches out till I finally got to the adjustable that really solved thje problem and I reassembled the job with it.
Docus on the absolute mastery of the 8 and 12 inch adjustable, the 440 channelocj, the 10R vise grip, have a collection of the 11R before investing in every table scheme, make sure you got saw horses, start a bench with a plate over horses before concocting every scheme you can read about.
So, owners are often their own problem. Like lawyers got to deliver bad news but forget about the fricken screw comp, get 5 hp 2 stage, can do about all the work as man can do and if I had to think blast would simply add another unit as needed, put a little wall around the master.

 

[sberry]

I had the 3 hp, if I didnt would have got 5, its too small for real paint, can stretch it with some tanks and air management but,,,, in the end when the process chances to stand by air its cheap quiet so much that didnt even complete the shroud was old from a service. Someone gave me a 5 with a big jug I cleaned, added a starter I found, cleaned it, as I recall it took me about a day or part of 2 and had it installed and acted as backup a time or 2, dont even have the breaker on. I was tempted last winter a time or 2 and simply let it pass for 5 minutes after 20 work, needed rest anyway.
You might want an expensive comp but its not the right tool for you at this point. I might store my research but this is a case where a more simple economical tool is not only as good but BETTER for the application. If you want to hedge you can get a little better recip, buy something common off the rack along with a few pieces of pipe, get ghoses, get reels get fittings, hav some in reserve to buy a tool when you need it.

 

[sberry]

Buy a nice one. Can use it in your old age, can sell it cause its in a class someone wants. That rotary is for BP running controls in a gas plant, small money to that, can match it to true continuous load, a schrew banker would recognize this. Its a good way to park a lot of capitol and effort and still not get it working right.
sr clyde,,, jake and I often seem to differ slightly but only in perspecitive of sorts. One thing he does is he buys well but knows exactly what he is going to do with it by then, he doesnt miss. He get some bargains when its right and buys a machine a step up used. I saw a big machine shop built this way,,,, guy could have no way bought this but it was a leapfrog where the machine rebuilder kept up grading, pretty quick had set up a 40 ft long lathe he got near scrap at a sale. He built up so he could rebuild and tailored the work that came in to the tools.

 

[seber]

If you assume electricity is 10 cents per kw hour and five hp uses 850 watts then that extra five hp costs $170 per year at 2000 hours/year. That is how much you will save with ten hp or variable speed vs fifteen hp. Hope that helps. (one hp = 746 watts plus efficiency factor)

 

[Packard V8]

Too bad you're half a world away. We've got a rebuilt 25hp Kaeser which would cover your needs with room to grow.

jack vines

 

[sberry]

There is a bunch of stuff in the fab biz that its hard to get enough of. A lot of what I would do today would depend on how difficult shopping was, easy to buy last minute etc? Lots of stuff passes, some I am glad I didnt get too committed to and didnt have a true passion for anyway. When I started there was no reason to think valve jobs wouldnt go on forever but I cant even remember the last time I ground a valve on a common passenger car or light truck. Despite some interest here engine machine has went away as a real going concern.
A guy has to hustle to do walk in work, these things are all different if a guy is a true business guy but simple speculation is such a buckshot aproach and very rarely does adding capacity before it arrives add to business, I know several good broke fabricators keep "adding to the capability" usually following some one off job they never do again and it clogs the place up.
I might find some sources where its equipment sensitive, farm some out, talk deals as you might be a repeat user, etc. Sometimes other vendors send some your way. There are a lot of fine welders gone broke from this.

 

[sberry]

There are other things associated that at first dont seem to go together. I got hot pressure wash, makes a big difference, I also paint. I got a couple dun rite customers and get rid of some others but the dun rights bring me fab work and when I turn it back all painted have no problem paying for the paint job I added on to the bill.
Now they kind of know and kind of expect it, never had them say not to and never had them fuss over paying for it.
The job started 1500 and ended up 3K but not cause I screwed them but because I value added it, fixed the trim, cleaned the glass, touched up the paint, all stuff with little to no equipment investment. Sometimes things a little harder or take a little longer especially for a 1 off guy but you didnt have another 10K machine to save 2 hrs work. took us 2 hrs to dig a ditch but we didnt need to deal with the digger, would have taken longer to save a little work along with the investment. Different if you are in the ditch biz, its a weigh decision.
A 1 man show has so much of it idle, I might make the day without using the comp if I try.
You asked a particular question but most that are not recomending a fall back in some thinking are doing a disservice to this type of thing, you might find a deal or the best in its class but its really the wrong tool.
The money that selling some of my old off would bring is minor and I do some contracting with it but I aint gonna buy new 5K welder to do 1 worth of work. It aint worth it. Might as well stay home and watch reruns, way cheaper. I dont take busy work from customers, I work on stuff they really want or need and try not to work on junk. I try to be available when it happens and not have a long list before I get to theirs cause I am backlogged with ****.
Had one come in and finished yesterday, they didnt expect it back till tomorrow and didnt blink when I charge a good scale for it. Try to meet the schedule.

 

[Phantomd]

Get a quote from Ingersoll Rand. When I quoted our 30horse they were the cheapest and it's been great.

 

[stonesfan68]

I’d urge you to reconsider purchasing a rotary compressor. They like to be run hard. If you don’t run them and get the oil up to the correct operating temperature then you get water in the oil and that’s no good. A one man shop is not likely to use the machine enough to get the benefits of the screw compressor.

If you insist on getting the screw machine then I’d make sure that you run it as much as possible, even to the point of opening up a line to atmosphere and letting the machine get warm.

Also, check your assumptions on the efficiency of a reciprocating compressor. At that power level the air delivery of rotary is equal to or less than a recip machine.

You can always build a small enclosed around a reciprocating compressor and install an inlet silencer to keep the noise down.

I’ve never understood the need for a VFD on such small compressor. It would take a long time to get a payback based on energy savings, particularly with such a low usage.

 

[drummerdimitri]

I’d urge you to reconsider purchasing a rotary compressor. They like to be run hard. If you don’t run them and get the oil up to the correct operating temperature then you get water in the oil and that’s no good. A one man shop is not likely to use the machine enough to get the benefits of the screw compressor.

If you insist on getting the screw machine then I’d make sure that you run it as much as possible, even to the point of opening up a line to atmosphere and letting the machine get warm.

Also, check your assumptions on the efficiency of a reciprocating compressor. At that power level the air delivery of rotary is equal to or less than a recip machine.

You can always build a small enclosed around a reciprocating compressor and install an inlet silencer to keep the noise down.

I’ve never understood the need for a VFD on such small compressor. It would take a long time to get a payback based on energy savings, particularly with such a low usage.

If that's the case, I should get the smaller 10 HP unit and not the 15 HP as the former has about twice the CFM I need today so it will give me enough headroom and run more often then the larger unit so there will be less water mixing with the oil as per your recommendation.

I think my decision has been made. Will be getting the Atlas Copco G7 FF without VSD because even my local sales rep said I have no need for it especially for such low air consumption.

 

[stonesfan68]

That Atlas Copco is a great machine and I'm sure that it will provide you with great service.

 

[matt_i]

Do you have the electrical service to support a 10 or 15hp motor?

Most residences in the US would be iffy with that amp draw on 240vac single phase.

Do you have a three phase service? Seems like there won't be a lot of rotary screw compressors without 3 phase motors....

 

[chrismenke]

I had to pay extra for my IR 7.5HP screw compressor to get single phase. I don't think IR offered any thing bigger in single phase.

 

[drummerdimitri]

Do you have the electrical service to support a 10 or 15hp motor?

Most residences in the US would be iffy with that amp draw on 240vac single phase.

Do you have a three phase service? Seems like there won't be a lot of rotary screw compressors without 3 phase motors....

The workshop is located in an industrial zone so 3 phase electricity is the norm.

I will have to switch to a 3 phase electrical control panel and study my power requirements before choosing how many amps to opt for keeping in mind the higher cost associated with a more powerful electrical installation.

 

[drummerdimitri]

I had to pay extra for my IR 7.5HP screw compressor to get single phase. I don't think IR offered any thing bigger in single phase.

I don't need single phase for the reason mentioned above so this is not an issue for me.

 

[sberry]

I dont use a lot of air, I use air a lot, or often enough that I want it standing. I am not sure how his air might compare to a 15 man body shop. That could vary quite a little. If I wanted complete headroom minus continious sand blast dor 15 men would need to provide for about 5 depending on the work style. The duty factor may go as low as 20%, about 20 hp, maybe even a little less depending on the amount of sanding refinish going on.

 

[sberry]

One man needs 5 hp, you can work 2 with some sharing, 7.5 runs 2 steady, 3 with some management, 4 or 5 from 10 in most cases will work and the avg consumption rating you see on tools is usually based on 100.

 

[sberry]

Basically whatever the customer needs

, I'd like to be able to provide with continuous investment from my end depending on how well the business is going.

I agree with this totally. Its why some of us caution about getting the correct equipment. A statement like this

Basically whatever the customer needs

shows some lack of focus here on things that will make money. Yes,,, its nice and its nice to have but it wont make any money and on this end you are not buying it to fulfill customer needs but to serve your needs to do the work the customer wants.
I am going back to dr clyde here,,,, this is something he does very well and a poster child for looking to procure to do the work he needs to do. An example is a plate beveller,,, do you have work for this? They make them, there are shops got them, only place in 40 years of general fab I have ever ran across one is in a shipyard. I wouldnt even know how much one cost.
If you ask you will get opinions on which is the best but from reading here I can almost bet following the nature of the work described earlier you got no use for it at this point. Its not something a guy can run around the neighborhood advertising.
If I was starting a small shop today it would be rather simple.
A feeder, a little stick, a torch, a plasma a chop saw and a couple grinders with a drill, sawzall and a bucket full of clamps. Another bucket of common hand tools. Most of it would fit in the back of a pickup.
When something came along looked like it was likely to repeat,,, different than tooling after every one off job,, I would look at tooling for it, start economical and see where it went and when it was practical would upgrade.
I wouldnt even have considered,,,, wouldnt even been a thought to thro a bucket full on that type of comp. On a list of 100 important items it would have been in the 2 or 300 range, it would be something I scored used and likely set up independent most likely to do blast work.
As was pointed out by someone else,,, assuming there was savings from running it 24 hrs a day it would take 10 years to pay back 10% You need a consultant and not a salesman. A salesman may get you what you ask for and sometimes they got to do that to make a sale but a value added one would get you a correct machine and he would be worth paying a premium price for.
I have had them do that,,, especially when buying options, the guy wanted me to come back later,,, he said,,, its nice but guys get them and dont use,,, see if you need it and can always buy it later.

 

[sberry]

I would be taking a really good hard look at demand. Hwd is gone here, got a call the other day for some pipe threading. Wouldnt be worth it to buy a new machine for in my position but could take it and it set up another job. The next job though wasnt some hi tool deal, a hammer and a few wrenches but the know how was critical.

 

[Dozerhand]

I've never been around little screw compressors but my experience with the bigger ones is they are all continuous run. I may be wrong but I would make sure the compressor you're choosing can be used for intermitant duty. For a small shop I would think that starting the compressor first thing in the morning and shutting it off last thing at night would cost a lot even if its running unloaded 90% of the time. Do your homework. Be real sure what you buy will due what you want it to do.

 

[drummerdimitri]

I've never been around little screw compressors but my experience with the bigger ones is they are all continuous run. I may be wrong but I would make sure the compressor you're choosing can be used for intermitant duty. For a small shop I would think that starting the compressor first thing in the morning and shutting it off last thing at night would cost a lot even if its running unloaded 90% of the time. Do your homework. Be real sure what you buy will due what you want it to do.

With regards to the intermittent duty, I am quoting this directly from their product brochure:

"Thanks to load/no load control,
the compressor controller switches
automatically to the optimum control
mode for high, low and intermittent air
consumption."

That leads me to believe that this compressor will have no issues dealing with continuous (plasma cutting) and intermittent air consumption (air tools).

That being said however, I've been hearing a lot of the same advice and it's really got me going back to the drawing board here.

Maybe a rotary screw isn't the best solution for me, but neither is a regular piston compressor for its shortcomings (not 100% duty cycle, loud, unclean air).

So I went back to Atlas Copco's website and found out they have an oil free piston compressor (LZ series) that is rated at 100% duty cycle with 0 % oil in the output air and comes with the option of a dryer and 500 L tank mounted.

It is also available in a 10 HP configuration so the only downsides I can see compared to the rotary screw is slightly less CFM (32.8 vs 38.2), a bit more noise (69 vs 65 dB) and a 16,000 h lifetime which is probably less than half of what a screw should last.

Not sure about the pricing yet, but if it's much cheaper this would be a much better alternative don't you think?

 

[stonesfan68]

That LZ will be relatively expensive and maintenance intensive. It is for medical and dental air applications. It has a microprocessor controller on it. That's not going to be cheap to replace. Get a price for an overhaul kit to see what you are getting into.

The Ingersoll-Rand T30 series are rated for 100% duty cycle. I bet that Quincy and Atlas Copco's versions are, too. Note that it is highly unlikely that you will be using the machine at 100% capacity anyway. Most compressors are used at 70% or less.

In order to lower the noise level of a piston machine then install a Solberg inlet filter/silencer. You can also install the machine outside the shop or in a well-ventilated but well sound insulated room. You'll be wearing hearing protection in the shop for most air-operated tools, or at least you should be, so that's going to help, too.

 

[chrismenke]

So it seems camp is divided between industrial screw compressor users and piston compressors for small shops.

I had an in between which may help the OP make a more informed decision. 6 service bays, several air hogs (4'x3'x5' blast cab, continuous air feed to parts washer, etc.).

We went with an IR 7.5hp screw because we had a shop under an art studio an sound mattered. Piston compressor that could have done the job would have been ~3k with pipes and about we paid double for screw. We went with an IR UP6-7.5-150 single phase with airdryer. This was circa 2004. It delivered 25cfm at 150psi, and when I say delivered, I mean that we never needed to stop sandblasting for another operation to proceed.

If you've got three phase, they make that machine with a 10 and a 15hp air head.

It was dead nuts quiet (the enclosure built around it turned out to be more about
compressor protection rather that sound deadening). Ours sat on a tank...I think 120 gallon. When the shop was really running full bore, it seemed to stay on rather than cycling, but during off hours it would cycle similarly to a piston compressor. I talked to IR (both sales and engineering) and they said that these smaller compressors were not deigned to be continuous duty and could cycle happily for a long service life.

I've long since left that business behind me, but when I did the compressor was still operating as new, with something like 4000 hours on it. Not much for a factory compressor but huge for a small shop.

The industry has created a machine to fill that medium duty need, and I can't tell you how much I enjoyed the loudest compressor noise in the shop being the auto condensation drain.

 

[sberry]

It's not good to save 10% in power if it takes 10 years to save that 10, would take 100 years to pay it back. The post above said he had 6 bays working, that is also different demand. So is blasting with ongoing work. 2x the cost wasn't bad and said shop going "full bore" which is significantly different than 1 or 2 men.
As for preference between the 2 it doesn't matter to me, if someone gave me a new screw that cycled would take it. I just point out the difference in actual demand and duty cycle vs per dives or assumption or total speculation,, they call those wag,,, mine is a bit more a swag.

 

[drummerdimitri]

That LZ will be relatively expensive and maintenance intensive. It is for medical and dental air applications. It has a microprocessor controller on it. That's not going to be cheap to replace. Get a price for an overhaul kit to see what you are getting into.

The Ingersoll-Rand T30 series are rated for 100% duty cycle. I bet that Quincy and Atlas Copco's versions are, too. Note that it is highly unlikely that you will be using the machine at 100% capacity anyway. Most compressors are used at 70% or less.

In order to lower the noise level of a piston machine then install a Solberg inlet filter/silencer. You can also install the machine outside the shop or in a well-ventilated but well sound insulated room. You'll be wearing hearing protection in the shop for most air-operated tools, or at least you should be, so that's going to help, too.

Maintenance intensive? How so?

It doesn't even have oil or oil filters to be changed so if anything it should be cheaper to maintain (air filters, bearing to be changed?). It's also direct driven so no belts have to be replaced...

Also, even the screw compressors have a microcontroller built in so I don't see that being any different. I find it extremely useful to be able to monitor your load/unload times, set the pressure band, have a maintenance scheduler etc. built in. Things you never find on conventional oil flooded piston compressors.

I'm liking the idea of oil and water free air as that means longer plasma consumables life and that results in lots of $ saved in the long run.

If it's similar in cost to the screw compressor, it would be a better option for my use case right?

 

[allinon72]

You said you weren't looking for advice but I'll provide it anyway I'm a project manager for a large carwash chain and we installed 12 rotary screw compressors over the last several years and recently just yanked them all out because of extremely high maintenance demands and unreliability (both Sullair and ELGI brands). A carwash uses less air than an industrial factory, for example, but certainly more than what you described, yet still the compressors were not running enough to stay reliable. Screws like to run continuously. For that reason I would caution against this type of compressor.

 

[drummerdimitri]

You said you weren't looking for advice but I'll provide it anyway I'm a project manager for a large carwash chain and we installed 12 rotary screw compressors over the last several years and recently just yanked them all out because of extremely high maintenance demands and unreliability (both Sullair and ELGI brands). A carwash uses less air than an industrial factory, for example, but certainly more than what you described, yet still the compressors were not running enough to stay reliable. Screws like to run continuously. For that reason I would caution against this type of compressor.

Again, I'm convinced that a screw is probably not the right option for me right now. If you read my above post, I seem to have found a better alternative that would suit my needs better.

 

[MacMcMacmac]

You said you weren't looking for advice but I'll provide it anyway I'm a project manager for a large carwash chain and we installed 12 rotary screw compressors over the last several years and recently just yanked them all out because of extremely high maintenance demands and unreliability (both Sullair and ELGI brands). A carwash uses less air than an industrial factory, for example, but certainly more than what you described, yet still the compressors were not running enough to stay reliable. Screws like to run continuously. For that reason I would caution against this type of compressor.

I can only imagine how much condensation was in the oil of a lightly used screw in a car wash application.

I would caution against using a non-lubricated anything unless it was absolutely necessary. They are always more trouble prone in my experience. You don't get non-lube operation without some special design and materials like carbon or teflon rings and wear guides that never seem to last as long as they are supposed to and which seems to always be a few weeks back ordered due to the low volumes of sales of those parts.

I don't know what the temperature is like in your part of Lebanon, but keeping it hot enough should not be a problem if it is constant run. Unloaded screws don't use a whole lot of power. The thermal mixing valves will keep the oil temperature where it needs to be as long as its running.

If the price point is good, and the local dealer is reliable, knowledgeable and keeps wear items in stock, an Atlas Copco should be a safe bet. I don't think a VSD is a great way to spend your money, but I don't know what power prices are like in Lebanon either. The quality and training of the service personnel gets to be pretty important with increasing machine complexity. I'd put the extra money into the biggest vessel you can reasonably afford and fit in the shop, along with the best piping network the budget allows. Don't neglect proper airline filtration either, and stick with a brand you know you will be able to get new filters for. I assume you would get Copco filtration as well. Copco tends to be pretty pricey on their filters, but it is usually easy to cross reference them to any number of aftermarket suppliers.

 

[Gotcha640]

I totally get the desire to get the best of the best for a hobby shop, but any 10-15hp 2 piston with a big tank and correctly sized filters and dryers will be fine.

As above, look at any 5-10 man race shop, machine shop, sandblast/powder coater, body shop. They're all doing fine on a large unit from the local big box store or a small/medium commercial thing. All under $5k.

 

[cnc-me]

That LZ will be relatively expensive and maintenance intensive. It is for medical and dental air applications. It has a microprocessor controller on it. That's not going to be cheap to replace. Get a price for an overhaul kit to see what you are getting into.

The Ingersoll-Rand T30 series are rated for 100% duty cycle. I bet that Quincy and Atlas Copco's versions are, too. Note that it is highly unlikely that you will be using the machine at 100% capacity anyway. Most compressors are used at 70% or less.

In order to lower the noise level of a piston machine then install a Solberg inlet filter/silencer. You can also install the machine outside the shop or in a well-ventilated but well sound insulated room. You'll be wearing hearing protection in the shop for most air-operated tools, or at least you should be, so that's going to help, too.

Yes, just put it in another building, no noise at all. Although it doesn't really matter your making so much noise anyway.

 

[sberry]

Some noise doesnt bother me. I dont mind hearing it run a little. I notice if something sounds different and agree,,, guy sanding is making a racket anyway. Shielding is good, you need to hear the phone and its nice to be able to talk on it where you are without running and hiding out but a little noise in a shop isnt a big deal. Would be different if it was running near capacity continuous also. But most fab work is non air use, the real hours are, we do 4 1/2 electric for anything humanly possible,,,, its my tool and I can sharpen a razor blade with it.

 

[sberry]

I totally get the desire to get the best of the best for a hobby shop, but any 10-15hp 2 piston with a big tank and correctly sized filters and dryers will be fine.

As above, look at any 5-10 man race shop, machine shop, sandblast/powder coater, body shop. They're all doing fine on a large unit from the local big box store or a small/medium commercial thing. All under $5k.

I know 1 uses 2 box store 5 hp and has a crew busy as beavers. He didnt even master slave them, simply plumbed both on with the factory settings, If a guy is sanding they come on almost the same time. Puts some hours on each, it doubled the tank reserve and its got fast enough recovery. Puts out 2x a man sanding.
I installed them near 30 years ago. We talked about this a little at the time. Had a rural single service, someone had put in 150, he got the first unit little used for 400$, in about a year found another one and we set it right beside and a whip to the panel, t it to a 3/4 pipe and away he went. I fix a starter on 1 once, changed oil about once and maybe belts, I cant recall, but 2 smaller motors were so much better on the line. Worked till he retired and had custom car place, had 1 steady guy and a couple that came and went. They did a little plasma and mig, some lights. That was all the power stuff he ever had besides a fridge and run the furnace. Had a little bitty shallow well.
They were big 5, they made good air and the 2 of them together made for pretty fair sandblast for automotive. They had a pot and a hose out back and a pretty decent cab he scored somewhere. They didnt need to run a bunch of other **** when they blasted. Wasnt worth it to do anything better.

 

[drummerdimitri]

Ok so after having discussed the idea of an oil free piston compressor with my Atlas Copco dealer, it is clear that a screw would be better suited for my application as the LZ is not available and will cost significantly more so I decided it would not be worth it.

Now I'm back to deciding between the 10 and 15 HP models and to run a sandblasting cabinet along with a plasma cutter, the former would be enough as I can only do so much by myself at once but eventually, I will most probably be purchasing a CNC lathe and mill so would it not be better to get the 15 HP model for only 500$ more? I always hear things like "buy the most biggest compressor you can afford" and "you can never have enough compressor", so does this also apply to my case?

Another thing that hasn't been clear to me is the whole idea of load/unload operation in a screw compressor. I only have experience with piston compressors so do they work the same way? Will the screw run to fill the tank to its programmed pressure and stop? Will it then turn back on once the pressure in the tank falls below a programmed threshold?

I've read that some screws can run without producing any air so in what circumstances does it do that and for what purpose?

 

[MacMcMacmac]

The inlet valve closes. The compressor produces a very small amount of air that is blown off through a muffling device. Some units will have a timer that will allow the compressor to run for a preset period and shut off if there is no demand. Others will simply continue to run in the unloaded state indefinitely. All screws need some residual pressure for oil circulation, unless it has a separate oil pump, which is pretty rare nowadays.

 

[drummerdimitri]

The inlet valve closes. The compressor produces a very small amount of air that is blown off through a muffling device. Some units will have a timer that will allow the compressor to run for a preset period and shut off if there is no demand. Others will simply continue to run in the unloaded state indefinitely. All screws need some residual pressure for oil circulation, unless it has a separate oil pump, which is pretty rare nowadays.

Thanks for the info.

Do you happen to have a video of this in action?

Would make understanding exactly how this works easier.

 

[sberry]

I was kind of going along with this, I been at forums long enough to spot it. I have done this a couple times and didnt have any of it. Did it that actually worked for a while with a truck body next to a power pole with 100A service and a buzzer and a torch. Had a friendly steel yard we could sketch up a shear and bend list.
I did another pretty good size deal one time where they quoted and it was some kind of astronomical cost to get it all chopped up and then he says, we cut by the hour too,,, well duh and I did get a couple bottles for the shop help but it was some insane cheap number like 35 or 40 an hour and some of the guys billed 1/2,, ha so I went right in with a bunch list and about the end the manager caught me rigging in the back and I had to stand and watch but that was cool too, so I often used 2 machines. Sheared plate and the other guy would bandsaw to sticks a time. I be gone in 30 minutes with my 250 dragging ***, 114 parts chopped in 30 mins shop.