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Splash vs Pressure vs Rotary Compressor

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  • Splash vs Pressure vs Rotary Compressor

    I'm looking to purchase a larger compressor for my shop and have hit a wall on decision making.

    A friend has a 10HP Ingersoll rotary screw that only puts out 26cfm that he is looking to sell. I've heard that those compressors are not good for light use but nobody actually says why. It also seems like a big motor for relatively low cfm.

    I have an Ingersoll dealer close by that can get me almost anything in the catalog but suggested a 7.5hp 80gal 2 stage model. I've also been looking at Quincy & Atlas Copco with the same specifications but they have splash and pressure lubricated pump options.

    My usage is a one man shop with plasma cutter, die grinders and a small blast cabinet. I plan on getting a larger blast cabinet (but still compact) and a cnc plasma table.

    > Would the 10hp rotary screw end up having problems from such light use? Only thing I've read is that they like to have constant run for the oil temp. Here in FL where my shop is 80°+ that may or may not be an issue.

    > Is a 7.5hp 80gal (24cfm) overkill or go with a 5hp 80gal (19cfm)? I know both are probably over my actual requirements but the tank would fill quicker.

    > For my light use is the pressure lubricated pump a good idea or just put the extra $500 towards the auto drain and piping in the shop?

    > Has anyone had any experience with the Atlas Copco models? Cant find anything for reviews and since there are small portable compressors shown on their website I'm wondering if their non rotary screw models are made by someone else since they are a little cheaper than an IR.

    > My shop has 100A/240V/3PH power and the only load would be lights and the plasma while the compressor would need to run. The 10hp R.S. seems way overkill but a reciprocating starts harder. Would the load of a 10HP rotary screw be close to a 7.5hp reciprocating since it has to turn a large flywheel and when running is that 10hp motor actually being used at capacity? (I've never looked into rotary screws so not sure how they function)

  • #2
    You may be confusing the methods used for lubrication and the methods used for gas compression.

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    • #3
      Pressure lube is, in my opinion, best. 7.5 hp will provide all the air you'll likely need. In most cases a 5hp will be single stage, a 7.5 may be either single or, more likely two-stage. As for speed of filling, keep in mind that the two-stage pumps are typically set to fill to 175psi. while the single-stage is usually around 130psi.
      Last edited by chipmaker4130; 09-06-2021, 06:16 PM.
      Southwest Utah

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      • #4
        Originally posted by Bented View Post
        You may be confusing the methods used for lubrication and the methods used for gas compression.
        I'm on the fence between the rotary my friend has with 21K hrs but just had a full service and air end shaft seals replaced or a new piston type.

        With the piston compressors I dont have experience with the pressure lube pumps to know if its worth the extra cost.

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        • #5
          Originally posted by chipmaker4130 View Post
          Pressure lube is, in my opinion, best. 7.5 hp will provide all the air you'll likely need. In most cases a 5hp will be single stage, a 7.5 may be either single or, more likely two-stage. As for speed of filling, keep in mind that the two-stage pumps are typically set to fill to 175psi. while the single-stage is usually around 130psi.
          I cant find any pricing online for the Atlas Copco pressure lube ones but here are the standard ones I'm looking at.

          The Quincy is around the same price but without the built in cooler. The Max package is about $800-1k more with cooler and auto drain.
          Attached Files

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          • #6
            Atlas Copco is, to me, a premium brand. Only thing wrong with them is the price! See if you can determine the maker of the motor on anything you're considering. I'm personally still in favor of the US made Baldors, and I used to think WEG was a decent brand but not so sure any more.
            Southwest Utah

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            • #7
              Originally posted by Chris165 View Post
              I'm looking to purchase a larger compressor for my shop and have hit a wall on decision making.


              I have an Ingersoll dealer close by that can get me almost anything in the catalog but suggested a 7.5hp 80gal 2 stage model.
              Oh heck yeah! I would negosh on that pump. She is fat at 80gals, she is about 8 Gals! LoL.. JR

              Horizontal or vert? Vert not so bad.



              I would pay 1300.. JR

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              • #8
                Originally posted by JRouche View Post

                Oh heck yeah! I would negosh on that pump. She is fat at 80gals, she is about 8 Gals! LoL.. JR

                Horizontal or vert? Vert not so bad.



                I would pay 1300.. JR
                Yeah it is quite large, going to be fun getting vibration isolators under it. 80gal vertical is the best option for my space. The 10hp rotary screw would eat up a bunch more valuable space.

                I wish I could get one for $1300😂



                I've recieved quotes for different brands (IR, Champion, C.A.S., Curtis) and the cheapest was $2,800 for a base model 5hp/3ph model all the way up to almost $5K

                Compared everything and it looks like a Curtis CA series 7.5hp/3ph 80 gallon full package model is going to be the winner because of the fair unit cost and full 5yr warranty including P&L + on site repair as long as OEM service kits are used.

                Havent heard much about that brand but after some research they seem to be very well built industrial units which shouldnt give me any problems for my one man operation.

                Comment


                • #9
                  Originally posted by chipmaker4130 View Post
                  Atlas Copco is, to me, a premium brand. Only thing wrong with them is the price! See if you can determine the maker of the motor on anything you're considering. I'm personally still in favor of the US made Baldors, and I used to think WEG was a decent brand but not so sure any more.
                  I can vouch for Atlas Copco, they are indestructible. And not cheap. I installed the plant compressor at my old job, an Atlas Copco with 160 CFM continuous at 125 PSIG. 30kW screw compressor with cooler, cost about 100k. It has run 24 x 7 x 365 for the last 5 years, with only one or two scheduled shutdowns per year for oil and filter changes. Otherwise it is literally continuous.
                  25 miles north of Buffalo NY, USA

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                  • #10
                    Originally posted by nickel-city-fab View Post

                    I can vouch for Atlas Copco, they are indestructible. And not cheap. I installed the plant compressor at my old job, an Atlas Copco with 160 CFM continuous at 125 PSIG. 30kW screw compressor with cooler, cost about 100k. It has run 24 x 7 x 365 for the last 5 years, with only one or two scheduled shutdowns per year for oil and filter changes. Otherwise it is literally continuous.
                    I was really leaning towards the Atlas units but one of my factors was local service/support.

                    They listed a local service center (Orlando Fl) but the number was out of service. Called A.C. main number and was given another service branch down here which I also got the same "this number has been disconnected" message. Thought that was kind of strange.

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                    • #11
                      Originally posted by Chris165 View Post

                      I was really leaning towards the Atlas units but one of my factors was local service/support.

                      They listed a local service center (Orlando Fl) but the number was out of service. Called A.C. main number and was given another service branch down here which I also got the same "this number has been disconnected" message. Thought that was kind of strange.
                      Wow thats weird. The compressor at my old job was purchased through their electrical parts supplier (we had our own in-house electricians). Instead of dealing directly. Given the recent supply chain disruptions I'm not surprised about the Orlando number.
                      We did our own service after installation -- as long as you follow the manual verbatim they are good on the warrantee parts. The filters and the oil add up, though depending how much you actually use it.
                      Last edited by nickel-city-fab; 09-11-2021, 11:00 AM.
                      25 miles north of Buffalo NY, USA

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                      • #12
                        I've been running a 5 hp, 80 gallon vertical tank for about 20 years on 220 1 ph. The compressor is an old, old Sears Craftsman 2 stage and the motor is an old REAL 5 HP with a 10" diameter. The pump will do 175 PSI, but gets pretty hot. I turned it down to 125 and it works fine, fills up fast. Most air tools run on 90 PSI, and the 80 gal. tank has a good buffer zone. Vertical takes up way less space than horiz.

                        I have a cabinet blaster, lots of air tools and several drops with air nozzle. When I'm blasting, the compressor will come on, fill up, and shut off for a while. It easily keeps up. Same with running rotary air tools that use a lot of air. Maybe this will give you some guidelines to go by.
                        Kansas City area

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                        • #13
                          What shop air pressure do you need?
                          Plasma cutter, what pressure.?
                          Blast cabinet, a solid dependable 100psi should do fine.
                          7.5hp will give you the volume you need for 1 man, but at what pressure?
                          An aftercooler between the pump & tank is a good thing if you can swing it into the price.
                          Single stage will yield higher volume at lower pressure.
                          Two stage comes into play if your actual needed pressure is above about 120

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                          • #14
                            No experience with the Atlas Copco, but I do use a Quincy on a regular basis. It's the 80gal. vert. tank QT-5 model, 5hp 230v 1ph, 2-stage splash lube that is rated for 17.2cfm @ 100psi and 16.3cfm @ 175psi. For a one man band operation I couldn't ask for anything more. Hooked up with a tight quarter turn valve on the output the tank stays full when not in use which saves startups when only needing a quick blast of air. Pressure regulator drops the shop line down to about 120psi max. More than enough for what's going on, and that includes feeding air through a dedicated regulator to the waste oil burner in the winter. Nothing fancy on the water drain. Just another little quarter turn valve and a drain pipe to take the water away from the working area. Open it once a day in humid seasons, once a week in the drier winter months. Simple works best here. Again, not sure how it stacks up against the Atlas, but other than some teething pain getting the right sized magnetic starter I've zero complaints about the quality and reliable operation over the past approx. 10 years.

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                            • #15
                              Originally posted by Toolguy View Post
                              I've been running a 5 hp, 80 gallon vertical tank for about 20 years on 220 1 ph. The compressor is an old, old Sears Craftsman 2 stage and the motor is an old REAL 5 HP with a 10" diameter. The pump will do 175 PSI, but gets pretty hot. I turned it down to 125 and it works fine, fills up fast. Most air tools run on 90 PSI, and the 80 gal. tank has a good buffer zone. Vertical takes up way less space than horiz.

                              I have a cabinet blaster, lots of air tools and several drops with air nozzle. When I'm blasting, the compressor will come on, fill up, and shut off for a while. It easily keeps up. Same with running rotary air tools that use a lot of air. Maybe this will give you some guidelines to go by.
                              That sounds like a good one when things were built to last. I've been using an older 30gal belt driven oil lube Husky for a while but the plasma keeps it on continuously and dont even think about running the blast cabinet.
                              Right about the 80gal giving a buffer, my friend has a 60gal and his plasma kicks it on really fast.
                              My blast cabinet is a fairly small benchtop one but I'd like to get a floor model with a little bigger work area. They all seem to be close to the same CFM.

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