Quiet Air Compressor

[Gary C.]

Re: Quiet Air Compressor

Article written for the Texas Chapter Talepipe Newsletter on compressor plumbing that might be of interest

[Gerald C.]

Re: Quiet Air Compressor

I'm trying to determine what compressor I should really get for running my HB blast cabinet. The Craftsman compressor I have now has:
My current compressor specifications are:
20 Gallon Tanks
4.3 @ 90 PSI for scfm
155 PSI


Yet, it doesn't keep up with the sandblasting in my small blast cabinet. Should it or should I get something with more scfm?

Thoughts??

Thanks

[Joe R.]

Re: Quiet Air Compressor

Gerald,

I am not surprised one bit that your compressor can't keep up. Sandblasting takes lots of airflow (CFM). I know patience is a virtue, but I don't have the patience to wait around for the tank to fill up after blasting briefly. I got me a Quincy QT-5 and never looked back. Sure it wasn't cheap, but it performs well for any job I have thrown at it.

Joe

[Gary R.]

Re: Quiet Air Compressor

I'm trying to determine what compressor I should really get for running my HB blast cabinet. The Craftsman compressor I have now has:
My current compressor specifications are:
20 Gallon Tanks
4.3 @ 90 PSI for scfm
155 PSI


Yet, it doesn't keep up with the sandblasting in my small blast cabinet. Should it or should I get something with more scfm?

Thoughts??

Thanks

Hi Gerry,
My setup is the min to make it work. A lot depends on nozzle size as well. The TP cabinet I have, 780TL, needs about 15 cfm at 90 psi to work. The Eastwood compressor, with the scroll setup, is said to be close to that CFM and works as I have been using it for the past 6 years. I have a Craftsman oilless compressor I used for years before I setup my current shop. It is fine for using air tools but is it not going to last for blasting, and you will be deaf if it is close by. You have been to my shop and know it's a "submarine" setup, meaning using all the space I have, and everything is on wheels. The compressor I have was one of only a few that I found at the time that would work. The Eastwood one is smaller and much quieter than the others but it's a good investment too. I am not sure of the current price but would guess it's over $2000 now. For intermittent use you still need to get more cfm or sub out the work. I use cabinet most days, the compressor is on every day.

[Joe R.]

Re: Quiet Air Compressor

I'm trying to determine what compressor I should really get for running my HB blast cabinet. The Craftsman compressor I have now has:
My current compressor specifications are:
20 Gallon Tanks
4.3 @ 90 PSI for scfm
155 PSI


Yet, it doesn't keep up with the sandblasting in my small blast cabinet. Should it or should I get something with more scfm?

Thoughts??

Thanks

I have an old 3 hp, 14 CFM 2-stage compressor that just barely keeps up with the blast gun that came with my medium-sized TP Tools blast cabinet. It runs off a single-phase, 20A, 220 Vrms power outlet. This capacity is probably the minimum level you should consider for continuous blasting.

When selecting a compressor, pay attention to the power requirements for the motor. One-phase power is probably preferable unless you have 3-phase power coming to the premises. You may need more than 20A, 220 Vrms outlet if you want to go above 3 hp.

Another thing to be aware of is that compressors come in either single-stage or two-stage configurations. Most single-stage compressors deliver air at about 90 psi, which is probably adequate for blasting if you have enough CFM to maintain that continuously.

A two-stage compressor uses a second cylinder to further compress the output air from the first cylinder. Two-stage compressors can achieve output pressure of up to 200 psi.

I've never compared the cost of single-stage compressors to two-stage compressors, but it's possible that for the same CFM, a single-stage compressor might be less expensive but still adequate for blasting.

[Thomas S.]

Re: Quiet Air Compressor

very quiet. Plan for 220V for more options. I have an upright tank portable model.

https://www.quincycompressor.com


Pricey, but super quiet even though oil-less.
https://www.californiaairtools.com

[Patrick B.]

Re: Quiet Air Compressor

I am surprised that scroll and oilless compressors are recommended as being quiet. I thought they were much louder than piston compressors. I have an old Sears 5 hp vertical tank two stage piston compressor and a much newer 1 hp small oil less Craftsman compressor. While neither of them is very quiet, the small oilless (scroll?) compressor is louder with a more obnoxious sound than the big piston compressor. Have oilless compressors changed for the bettor in the past few years?

[Gary R.]

Re: Quiet Air Compressor

No, the old Sears 5.5 hp compressor I have is oiless and noisy as hell. It would never last in a blast cabinet application.

The Eastwood compressor I have, shown in the past responses on this thread, is a scroll that uses oil. I just changed the oil and filters so it holds about 2.5 qts. It is the quietest compressor, in the size and CFM I found. I checked the rating with a meter 4' away and it was in the low 60Db range if I recall correctly. I think I posted it above. I don't even run it with the metal enclosure on it which would cut down a little more.

Years ago when I was a Facilities Manager we bought a piston compressor, from Home Depot. It was 240 1 phase and I forgot was the CFM was but it was the largest one they had. It was noisy but it was in a back room suppling air to a small screw machine shop. It lasted about a month before it burnt out. The Shop manager was cheap and bought cheap, that is what happened. I went out and bought a $10k IR 10hp piston and it ran that shop until it closed. I sold it for $1000. It was noisy too but not as bad as the junk from Home Depot.

So really, like anything else, depends on application. The Sears I have won't work, the Eastwood does. I don't think I would try to really blast without at least 12-15 cfm. When I had my cabinet at my old job I had (2) 50hp screws running and air was never an issue.

[Patrick B.]

Re: Quiet Air Compressor

Thanks Gary for the explanation. I have always equated “oil less” and “scroll”. Now I know that is not correct. Do you think that scroll compressors that use oil are quieter by nature than piston compressors or that you just happened to find one that met your expectations?

[Thomas S.]

Re: Quiet Air Compressor

Agree with you 100% on the Sears Oiless and virtually everyone made -they are extremely noisy!!

However the California Air dB rating is well below most piston type compressors so that would be the exception. They use dual-cylinders and are Teflon coated. Again, you have to go by the published dB ratings. the dB scale is geometric not linear so a 10dB difference

If you are not comparing the dB levels then you really can't know for sure which one is quiet. Scroll compressors are quiet as well becasue of their mechanism (no up and down motion) but are usually much more expensive.

• Under 60 dBA – volume of typical conversation, very quiet compressor
  60-80 dBA – volume of a restaurant, medium quiet compressor
  Over 80 dBA – volume of a vacuum cleaner or above, noisier compressor

[Gary R.]

[Mark F.]

Re: Quiet Air Compressor

Also, remember that sound pressure levels ("SPLs" derived from sound power levels) follow the Inverse Square Law (ISL) with regard to distance from a point source. Other physical agents like ionizing radiation also follow ISL.

Lots of math involved in determining correct measurement techniques; scales; interferences; reverberation; etc., but suffice it to say if you:

• double the distance from a point source with a known SPL (aka, intensity), the intensity at 2x the distance will be 1/4th of what it is at the source
• triple the distance from the point source and the intensity at that 3x distance will be 1/9th of what it is at the source
• quadruple the distance from the point source and the intensity at that 4x distance will be 1/16th of what it is at the source
• and so on...

So, distance is your friend if you're trying to get quiet.

Also, 3/4" plywood with some foam applied is an excellent sound barrier material, but you have to watch for reverberation, heat build up if you fully enclose the source - and a bunch of other things...

This link provides some visuals and calculators

http://hyperphysics.phy-astr.gsu.edu...Fm2%20%3D%20dB.

[Gerald C.]

Re: Quiet Air Compressor

Thanks Joe!

[Roger W.]

Re: Quiet Air Compressor

Gary,
How do you like your Eastwood Scroll Compressor. I am thinking of getting one. The tank on my old Sears Compressor that I bought used in 1968 had a hole rust through it the other day.
Thanks Roger

[Gary R.]

Re: Quiet Air Compressor

Hi Roger,
Well I bought in on the first batch back in 2017. I had just setup shop at my house and needed a compressor that would supply the volume needed for blasting, tools, and general use. Mostly for blasting diff's, boxes, and TA parts. I have limited space so the conventional piston compressors would be too noisy and I didn't want to use one outside to cause an issue.

There wasn't a lot of offerings and decided to chance the new scroll from Eastwood. It was compact, 230vac 1 phase, and rated about 12-13 CFM.

I added an 80-gallon receiver in line to use with the 25-gallon tank the compressor had.

It is quiet, I don't keep the cover on it. I can work in the shop without needing hearing protection. For the most part the machine keeps up with the blasting I do. Sometimes it runs for 20 minutes while using a large nozzle. I stop to let it cool down during long runs.

The first machine failed 2 years into use. Eastwood stood behind it without any issue. I got to know the engineer for the machine and he is excellent. I recently had to replace the on/off switch which is a bleed down valve. I change the oil every 6 months and use their filters and oil. Knock on wood, it will be 3 years old in December.

Overall, I am very pleased with it. It is small, easy to service, and they support it. I don't know what the price is today but I'm sure it is a lot more than what I paid for it- but what isn't the past 3 years. I run inline filters, have drip legs plumbed in. I never had moisture at point of use inline. I don't spray paint though. I run 3/4 & 1/2" black pipe and use quick disconnects on all my tools.