News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

air compressors

Started by spolij, December 01, 2020, 03:14:45 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

spolij

I wanted to buy a sand blaster, The ad says it works on as little as 10 cfm. That's a $1000 min compressor
I saw an ad for this. It's used to fill scuba and other pressure tans. They don't say how many cfm only 30 MPa I don't know what that means. Can this be used with a reegulator and used for a paint gun?

High-Pressure Electric Air Compressor Pump 4500 PSI 30 MPa 300 BAR Adjustable Auto-stop High Pressure System Rifle PCP Paintball Fill Station for Fire Fighting and Diving (30Mpa Adjustable Auto-stop)

Clewisiii

All of those values are measurements of pressure not volume. 

You will need that 600 to 1000 dollar unit.   

"My interest is in the future, because I am going to spend the rest of my life there."  Charles Kettering

carlhungness

   Once again, please be more specific. What do you want to do with the sandblaster, that'll tell us what size compressor you need.

spolij

Carl the sand blaster i mentioned in my post is to clean up rust and crap on my 66. Not using it on the body. The unit i'm looking at needs 10 cfm. My compressor won't do that. However i did find an adequate compressor with 22 cfm for $450.

Thanks both for the help

TJ Hopland

That scuba thing is going to be VERY low volume but very HIGH (for air) pressure.   MPA I'm assuming is megapascal and 30 converts to around 4,400 PSI. 

A typical sand blaster is going to be high volume and not especially high pressure.    In theory if there isn't a pressure given you can guess maybe they mean 90 psi so 10cfm at 90 psi is going to typically be found on a mid quality or better 60 gallon or bigger unit.   

For the most part you are not going to find cfm's over about 7.5 on anything with say a 30 gallon or smaller tank.  There may be some oddball units with 30 or so gallon tanks that will do 10 cfm at 60 psi just for portable applications like some paint guns but those are not the low to mid range units and will likely cost as much or more than a 60 gal so you would only get one if it had to be portable.

Other thing to note is a compressor that will do 10+cfm at 90psi is going to be 220v so bedsides the space for a big tall tank you will need special power.   Even if you go smaller you can run into power issues on 120v units if you are very far from the breaker and trying to share with anything so for anything but a little one for filling tires you might as well do 220v.   Most of the mid range units come with motors that can be wired for 120 or 220.   This is assuming North America,  anywhere else the voltage game is different.   

You found a $450 new compressor that will do 22 cfm?  At what pressure?   If they are claiming 90 I would like to see a video of it doing that for more than a couple minutes.     Typically a 'cheap' unit that will do maybe 12 cfm at 90 is going to be closer to $650.    Now if the one you found is on some super sale then maybe.....     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

The Tassie Devil(le)

The thing to consider is not the amount of air a compressor will supply, but the size of the receiver (Tank) to hold the compressed air ready for consumption.

Air Tools, be it a Sand Blaster, or a Rattle Gun consume air like it is going out of style, and the reason for the large receiver is to hold sufficient supply for use.

As we all know, when using Air Tools, one isn't holding the trigger all the time, for hours, but on and off, on and off, again and again.   This allows the compressor to keep the Receiver up to the task of supplying the air.

I have a reasonable Compressor, which I can spray paint, inflate tyres, and use small air tools, but it doesn't take long to deplete the supply.   Mine cuts out at 150 Psi, but soon restarts when the pressure drops below 80 Psi. and can paint a car all day long, but when painting, the trigger is not on all the time.

Sand Blasting uses a LOT of volume.

BUT, a small, tiny Sand Blaster won't require as much as a commercial one.   Not sure what the small Shop Blasting Cabinets use, but I would consider those in the small variety.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

spolij

Here is the gear i'm talking about.

savemy67

Hello John,

I think the general consensus of those who have replied is correct.

Virtually all air tools for the home shop require no more than about 90 PSI to operate properly.  But air pressure is a secondary or even tertiary consideration, as virtually any compressor can be made to provide 90 PSI or higher pressure.

Your primary consideration when considering a compressor is volume, measured in cubic feet per minute or CFM.  If you want to run a variety of tools - from an air chuck to fill tires, to an impact wrench, to a paint gun, to a sandblaster - look at the CFM requirements of the tools you want to use.  If the tool that requires the most CFM requires 11 CFM, you need to get a compressor that can output that amount.  The next most important consideration is the size of the tank.  The bigger the tank, the more volume of compressed air can be stored.  This will reduce the cycling of the compressor, extending its useful service life, especially in high-CFM use like sandblasting.

I have a Campbell Hausfeld compressor.  It puts out about 11 CFM at 90 PSI.  It has a maximum PSI of about 130, and a 60 gallon tank.  It has a 220 volt single phase electric motor.  Among other things, I run a small sandblast cabinet with it, but the compressor is close to its limit with the sandblast gun I have.  I bought this unit new about 5 years ago for $450.  If my budget at the time was larger, I definitely would have purchased a bigger unit.

If you did find a 22 CFM compressor for $450, I have to assume that it is used.  This is OK, but you need to investigate.  Is the compressor a single stage or two stage?  Is it gasoline powered or electric?  If electric, is it a single phase motor or three phase?  How big is the tank, and is it an ASME certified tank (there will be a tag on the tank if it is)?  A 22 CFM compressor for $450 may be the steal of the century, or a disaster waiting to happen.  I can't over-emphasize that unless you know all about compressors, find someone who is near expert at compressors to go with you when you look at this compressor.

Feel free to PM me with your phone number, and I will call you regarding your compressor and sandblaster questions.

Respectfully submitted,

Christopher Winter

Christopher Winter
1967 Sedan DeVille hardtop

Bobby B

Quote from: spolij on December 01, 2020, 08:12:49 PM
Here is the gear i'm talking about.

John,
  Hi. I own that unit. I use it just for frames. Everything else goes in the big Blast cabinet. My 7.5 HP, 80 Gal Vertical tank can just about keep up with that, and you have to be a little conscientious with the trigger finger. If you're just doing small stuff, they make a hand-held gun you load with like a coffee can full of shot that you hook a compressor directly to, rather than pressurizing that large tank. It actually works well for everything other than large panels because you can pinpoint a spot as small as a quarter with it. That's a huge investment if you're not going to be using it more than a few times.
                                                                      Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

TJ Hopland

The oil less compressors generally have plastic pistons and are not known to be the longest lasting units out there especially with a continuous use like blasting or painting.  Oil stuff will generally last longer but even the pros don't use those, they use more of a screw drive setup. 

And now that we have info from a first hand user of that gun that says a 7.5hp 80 gal can barely keep up.   He didn't say what his was rated for or what it cost but the 7.5's seem to be in the 20 cfm range and about $2500.  Other note about a unit that size is its a 50amp circuit.   That takes big wire so if its very far from your breakers the cost ads up quick.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Bobby B

TJ,
  My Gardner-Denver puts out between 17-22 CFM at 140-175 psi. Sand Blasting with that unit or Glass Beading with my old Guyson Cabinet will cause that thing to constantly run, so you have to take it easy unless you want to burn your compressor pump out. Takes alot of air to run those devices. Would Love to have a Kaiser, but it's not in the cards right now  :-\.....................
                                                 Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

spolij

Here is a better pic of the compressor. I'm going to read all this again. Lot of info. But i think i'm stuck with this one and hope it lasts awhile. I have two other compressors. I could hook them together so i'd have more tank space. This was an unexpected expense. I didn't know the blaster needed 10 cfm. Now the car is taken apart ready for cleaning and paint. I don't see any options at that price.

spolij

Bob is this what your talking about? $65 at Eastwood. That would be worth a try.

TJ Hopland

I have seen those triple pump units and thought their thing was they make a quiet version so you can get decent capacity but quiet.   At $450 I don't imagine that one is going to be quiet.  Unless you have seen some reviews you really believe about that unit that say it can do the job I don't think I would try it.

Not sure about using 2 compressors together.  Never really thought about it but maybe worth some reading to see if there is a right and wrong way to do it.   Not sure if you would want check valves on them so they could not feed each other or on just one or neither?   I have used multiple tanks but not with multiple pumps.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

The Tassie Devil(le)

If you want to use multiple compressors, then each one will need a one-way valve in the supply lines to the Receiver so that each one is not being back-pressured by each other.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Bobby B

Quote from: spolij on December 01, 2020, 11:26:17 PM
Bob is this what your talking about? $65 at Eastwood. That would be worth a try.

Yes,
You can borrow mine if you want to try it. I haven't used it in at least 5 years. Sitting in the cabinet.
                                         Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

fishnjim

A bad case of catalogue-itis!   it's a costly investment if you're just an occasional user.
Then you have to think about the noise, space, and power requirements.   Eg:If you upgrade compressor.  5 HP takes a 50 A circuit = 10 GA wiring min.
You won't be satisfied, if the compressor doesn't match the tool consumption.   Ive been through this on the cheap gradual spend in the past.  All I got was a string of worthless used units.   If compressor runs continuously and the pressure goes down, it's not big enough.   You'll have to stop and let it build - wastes time.   What's more costly than wasting time?  Heat soak is bad for the motor life.   Also need storage space and a place to blast as grit will get all over.   Also need a consumables budget.   Nozzles wear, dust masks, grit, etc.
When I bought my new bigger cabinet to replace my chinese tool take out piece of junk that leaked so bad I had use outside, which I bought to do inside!, my old 5 HP 17.5 cfm, 175 psig 80 gal compressor was no longer sufficient.   Motor and starter burned up, but I had for 20+ years.   
The chinese tool take outs sell units that are very loud as you go up in HP and use more starting power.   
I settled on a 7.5 HP unit that has a 10HP Eaton compressor and just runs at a slower (750 rpm) speed,(same price as loud ones, uses less electric) so you don't have to upgrade the wiring for starter torque.   I got all the air I need, 80 gal tank, auto drain, and quieter than my 5 HP was.   I went horizontal this time, to save space (under the stairs) and easier for me to install.
You can also snag a used unit at a garage auction, etc.   Just taking a chance on condition.   Got to have a way/help to uninstall and move.

Most of the "oil less" units are rotary, like a Roots blower.   We used them commercially for breathing air supply, etc.   Pistons need lube.

savemy67

Hello John,

I have been a skeptic since birth.  Now that I am 65, I am a full-blown cynic.  Being a charter member in the church of everything-you-know-is-wrong has helped me avoid serious injury to my wallet.  Despite this, I do believe that we should continue to learn every day, so I am prepared to be enlightened.

I went to the MZB (MeiZhouBao) website, which has a copyright date as of today of 2017, and found this (pasted from the website):

"Zhejiang Meizhoubao Industrial&Commercial Co.,Ltd.is one of the manufactures soecializing in manufacturing all kinds of air compressors.We are a modern enterprise combining with research,development,manufacture and trading. Meanwhile we have first-class workshop,advanced production assembling lines,precise testing equipments and skilled staffs.The principle of our management is "Scientific Management and First-Class Service".

Our main products are direct-driven air compressors, belt-driven air rompressors , dental mute air compressors,gas engine air compressors and oilless air compressors which are widely used in hardware.pneumatic industry , agriculture,decoration,environmental protection,medical treatment and other industry.With novelty,outstanding quality and sincerity we got a good reputation from clients all over the word.

We sincerely welcome domestic and internationak clients to come to our company for visit and cooperation"

I know that there are people in China who speak and write impeccable English.  My guess is that none of them work for MZB.  I searched the website for ASME (American Society of Mechanical Engineers) and ASTM (American Society for Testing and Materials) and found no results.

Based on the 22 CFM rating in your posted photo, I found MZB model MZB-1200h-65 rated at 22.2 CFM.  I looked at the specifications and photo on the MZB website and noticed a few things that raised questions in my mind.

Your post shows a horsepower rating of 4.5.  The MZB website shows a horsepower rating of 1.6 x 3, along with a picture of the compressor showing three independent motors/pumps.  The MZB website photo also shows that the output from each pump goes into the tank, not to another pump.  In effect, there are three single-stage pumps on the compressor, each capable of 1.6 horsepower.  Whichever pump achieves its maximum output first, relieves the other pumps of having to output any more pressure/volume.  Unless there is some plumbing I can't see in the MZB website photo, the compressor is a 1.6 horsepower compressor.  Unfortunately, the three motors will consume more electricity than will benefit the compressor.

Another specification I noticed on the MZB website is that the tank size is 65 liters.  This equates to about 17 gallons.  Your post shows a tank size of 6 gallons, so I may not have the correct model.  Whether 17 gallons or 6 gallons, at 22 CFM - which equals about 165 gallons per minute - a 17 gallon tank at wide open throttle would be empty in about 6 seconds - a 6 gallon tank in less than 3.  My guess is that the manufacturer is accumulating the CFM like the horsepower.  So the compressor is really a 7 CFM compressor.

By the way, I did not see at what pressure the CFM is measured.  I did see that the compressor can attain a pressure of 115 PSI.  At lower PSI, CFM is greater, because a cubic foot of compressed air requires a greater volume of air to be moved at higher pressure than does a cubic foot at a lower pressure.  So the compressor, with a fixed stroke volume can not produce as many cubic feet of compressed air in a minute at higher pressure than it can produce at a lower pressure, since the strokes per minute remain the same.  My guess would be that the effective 7 CFM measurement was taken at a lower PSI.  Perhaps the useful CFM for sandblasting is in the 4 CFM range.

I don't own an MZB compressor.  I could not find where to buy one other than Alibaba or some other Asian outlet.  I suggest you may want to avoid this compressor, or send it back and get a refund.

I know there are engineers on this forum, so, like the man in the orthopedic shoes, I will stand corrected if I am off-base.  Sorry for the novella, but I want people to make a smart, safe choice when it comes to tools, so they can enjoy their Cadillacs, and working on them.  If you seek advice on this forum, I obviously have no problem providing it, but truly, this is

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

cadillac ken

It's the air volume.  Sandblasting uses a ton of air.  A large tank is essential or you will be overworking the motor and will experience what those here describe as "not able to keep up"  meaning the motor will run constantly and probably in the case of the "affordable" compressors will lead to an early death of the motor/motors.

In my shop I had a 5hp 30 gallon Speedaire that when sandblasting ran constantly and while it did the job it was not able to "keep up".  After a while I had to replace the motor with one from Grainger.  I now have an 80 gallon 30hp 3 phase Ingersol Rand. To say the least it keeps up.

Point is there are compressors that will work well and last but probably not in the price range of the hobbyist.  I would say treat it as an expense and an expendable purchase as you can compare it to the cost of having the car (or parts) sent out to be stripped.

hornetball

"The quality is appreciated long after the price is forgotten."

Now, if I could only get my cheap self to consistently live by this truth.  I'm getting better . . . .