Quincy 325 CFM at 90 PSI?

[bad_idea]

I have an older Quincy 325 I pieced together for my home garage. It is driven by a true 5HP motor at ~900 RPMs. From Quincy's spec sheets, I see it is putting out 18.64 CFM at 175 PSI. Does anyone have the spec for what the CFM is at 90 PSI?

I am trying to size the maximum sand blast nozzle I can get away with on the unit. I sandblasted the floor pans in my jeep with it last weekend with good results. HF pot blaster with a 5/32 nozzle. Pressure switch on compressor is set to 80/125 psi. I have a regulator at the compressor set to 90 PSI. I did not regulate or monitor the pressure at the sandblaster. It performed well for about 45 minutes at a time, continuous. I am curious if I can up size the nozzle to use a coarser grit, or if I am at the limit now.

I am also toying with the idea of adding a second air tank (have it sitting around), and stepping the pressure switch on the compressor up to 175 cutout. Only reason the pressure switch is set to cutout at 125 now is because that is the switch I had laying around. I pieced this unit together with bits I had scrounged up/laying around. I understand higher pressure and larger storage volume will not increase compressor output, only provide a larger buffer to running out of air. Would the larger volume of air net me higher CFM output for a long enough time blasting to justify the effort to install another tank and pressure switch?

 

[larry_g]

If you can run now for 10 minutes and then wait 5 minutes to recharge with the larger receiver you may run 20 minutes and then wait 10 minutes for the recharge. At the end of the day your run vs wait times are the same.. I would suggest that you get a pressure switch rated for the pressures you want to run and then try that before adding more receiver volume. Make sure that your tank (s) are rated for the pressure you are working at.

 

[Steve_P]

The CFM difference at 90 PSI will be very slightly more, maybe 1 CFM difference. I know this doesn't really help much, but if you look at two stage CFM ratings, they don't change that much from 90 to 175; at least for home shop style compressors that I've looked at.

 

[bad_idea]

Appreciate the input guys. Considering it worked just fine with the 5/32 nozzle, I think I'll leave good enough alone. No need to be greedy.

 

[Jswain]

Putting a 175psi pressure switch back in(as long as the tank is rated for it) would definitely help maintain your blasting pressure.

Also installing a regulator on the pressure pot, and having your line pressure higher will make a big difference(depending on size and length of the air hose). If you're 90psi at the compressor and using a 50ft 3/8" air hose you're likely blasting with quite a bit less then 90psi.

 

[Sumboodie]

The CFM difference at 90 PSI will be very slightly more, maybe 1 CFM difference. I know this doesn't really help much, but if you look at two stage CFM ratings, they don't change that much from 90 to 175; at least for home shop style compressors that I've looked at.

Cfm at 90 vs 175 will be a fair difference. Even 125psi that many compressors spec is a difference.

Like the r40 pump on my compressor is 59cfm at 125psi and only 53 at 175. 90... id guess around 65cfm.

Sandblasting needs ~25-30cfm for continous use is what I've found while researching. Was trying to make a ~18 cfm pump work out.

 

[bad_idea]

Putting a 175psi pressure switch back in(as long as the tank is rated for it) would definitely help maintain your blasting pressure.

Also installing a regulator on the pressure pot, and having your line pressure higher will make a big difference(depending on size and length of the air hose). If you're 90psi at the compressor and using a 50ft 3/8" air hose you're likely blasting with quite a bit less then 90psi.

The tank is rated for 200 psi, purchased new 6 months ago when I assembled the compressor (the couple tanks I had laying around weren't any good). I'll get around to installing a 175 PSI pressure switch one of these days. Hopefully this winter I will have time/funds to add the second tank, 175PSI pressure switch, and distribution piping throughout the shop.

Good call on kicking the line pressure up and regulating it at the pressure pot. Hadn't considered that, but makes perfect sense.

Sandblasting needs ~25-30cfm for continous use is what I've found while researching. Was trying to make a ~18 cfm pump work out.

I have to disagree with you here. 25-30CFM will blast faster, but not required. You could blast with a pancake compressor with a small enough nozzle - wouldn't recommend, but should get the job done. My Quincy 325 (rated at 18.4CFM at 175PSI) blasts pretty good, never had to stop and wait for it to catch up with a 5/32 nozzle.

 

[Sumboodie]

The tank is rated for 200 psi, purchased new 6 months ago when I assembled the compressor (the couple tanks I had laying around weren't any good). I'll get around to installing a 175 PSI pressure switch one of these days. Hopefully this winter I will have time/funds to add the second tank, 175PSI pressure switch, and distribution piping throughout the shop.

Good call on kicking the line pressure up and regulating it at the pressure pot. Hadn't considered that, but makes perfect sense.


I have to disagree with you here. 25-30CFM will blast faster, but not required. You could blast with a pancake compressor with a small enough nozzle - wouldn't recommend, but should get the job done. My Quincy 325 (rated at 18.4CFM at 175PSI) blasts pretty good, never had to stop and wait for it to catch up with a 5/32 nozzle.

Meant continuous use with a reasonable tip size.
18cfm can be made to work, just not ideal.

There is a #2 nozzle that is 1/8 which would be very small. Next up is a #3 at 3/16". More common for general use is a #4 or 5 (1/4" and 5/16")

They go up to 1" i think, though probably using that for commercial jobs.

 

[Jswain]

The tank is rated for 200 psi, purchased new 6 months ago when I assembled the compressor (the couple tanks I had laying around weren't any good). I'll get around to installing a 175 PSI pressure switch one of these days. Hopefully this winter I will have time/funds to add the second tank, 175PSI pressure switch, and distribution piping throughout the shop.

Good call on kicking the line pressure up and regulating it at the pressure pot. Hadn't considered that, but makes perfect sense.


I have to disagree with you here. 25-30CFM will blast faster, but not required. You could blast with a pancake compressor with a small enough nozzle - wouldn't recommend, but should get the job done. My Quincy 325 (rated at 18.4CFM at 175PSI) blasts pretty good, never had to stop and wait for it to catch up with a 5/32 nozzle.

What size/length air hose do you have feeding your pot?

I can easily run my 18cfm pump down @90psi (at the cabinet) using my suction blast cabinet. With the tank starting at 160psi and the line pressure up to the cabinet at 125psi.

I usually blast ~60-70psi(at the cabinet). And the 18cfm keeps up(maintains ~125psi in the tank) Shutting off maybe a minute after I'm finished blasting. All my lines are minimum 1/2", and 95% hardline(copper) then just a small jumper to the cabinet, 1/2" thought the pedal & into the gun.

 

[CGT80]

The last post is very similar to mine. real 213t 5hp baldor motor, 17.7 cfm @175psi pump run probably slightly faster than the rated 800 rpm, calculates out to 20 cfm average based on fill time of 5.5 minutes on an 80 gallon tank to 170 psi and a 1 minute cycle time from 135 to 170 psi. Most of my lines are 1/2" copper and the rest is 3/8" hose with high flow fitting where necessary. My foot pedal uses a 1/4 or 3/8" ball valve and I use the skat blast gun and largest tips which are rated 20-25 cfm. At 60-80 psi, I can blast continuous and never run out of air. When I had smaller lines, especially at the cabinet, I blasted at 100+ psi and didn't run out of air, but it wasn't as effective as more air and lower pressure. At 100+ psi, it can drop the pressure.



This is the nozzle I use:
Skat Blast® Large Ceramic Nozzle Combo 5/16" I.D. Requires 20-25 cfm. Operating pressure 60-100 psi.


5hp will only make so much air. At my compressor, the air is regulated to 135 psi and then into a 0.01 micron motoguard paper filter (it says 125psi max on the housing), then into the copper and at the blast cabinet it gets dropped to the final pressure. There is pressure drop as you go, so it is always better to regulate air close to the tool.

My plasma table runs off about 200 feet of 1/4" hose even though Hypertherm says to use 3/8" hose for that 7cfm at 90 psi. Well, the hose has tank pressure on it and then it gets regulated and filtered right at the plasma cutter. There is never a problem keeping it at 100 psi while cutting. All the extra pressure from the 2 stage compressor eliminates pressure drop problems vs. single stage or pressure switches that max out at 125psi but drop to 90-100 before running again, which is too low by time the air gets to the tool.

80 grit garnet and 100 grit aluminum oxide work very well in my cabinet. That is what is needed for powdercoating parts and it is much faster to remove rust and coatings vs. the finer media I tried to use before. It makes a big difference to use new vs. worn out abrasives and coarser grit is far better if you can get away with it.....it applies to blasting, sandpaper, 2x72 belts, and grinding discs, even surfacing discs. Going too coarse, of coarse, can be awful if you get bad surface finish or don't have a way to take out the larger pits or scratches and too fine is very time consuming.

I think my uncle used mostly 1/2" nozzles and they usually ran a 175 cfm compressor and of course large pressure pots, for working on generator turbines for power plants and other related equipment. They ran that size compressor balls to the wall to purposely get the air so hot that moisture was not a problem. It is amazing how much faster that size setup is, although my cabinet still surprises me since doing the upgrades. Doing smaller parts in my cabinet is no big deal, but using the same size gun for a vehicle would feel like a night and day difference, I'm sure.

 

[larry_g]

Pressure switch on compressor is set to 80/125 psi. Only reason the pressure switch is set to cutout at 125 now is because that is the switch I had laying around. I pieced this unit together with bits I had scrounged up/laying around.

Does the pressure switch your using have any adjust-ability to it or is it a fixed unit? Most pressure switches are adjustable and very likely you could adjust this up to 150 psi or so.

lg

 

[bad_idea]

Thanks for the input guys, gives me more to chew on.

What size/length air hose do you have feeding your pot?

I have ~3' 3/4" piping coming off of the compressor, with a 100' 3/8 hose.

Does the pressure switch your using have any adjust-ability to it or is it a fixed unit? Most pressure switches are adjustable and very likely you could adjust this up to 150 psi or so.

lg

It is an adjustable one. Unfortunately the combo water separator, pressure regulator I have just off the compressor is only rated to 125PSI. Putting the compressor together turned into an evolution that cost much more than I initially planned. By the time I got to the distribution piping, the budget was tapped. I just used junk I had laying around. I hope to upgrade the piping system this winter, and will step the system up to 175PSI then.

 

[Jswain]

Thanks for the input guys, gives me more to chew on.


I have ~3' 3/4" piping coming off of the compressor, with a 100' 3/8 hose.


It is an adjustable one. Unfortunately the combo water separator, pressure regulator I have just off the compressor is only rated to 125PSI. Putting the compressor together turned into an evolution that cost much more than I initially planned. By the time I got to the distribution piping, the budget was tapped. I just used junk I had laying around. I hope to upgrade the piping system this winter, and will step the system up to 175PSI then.

That's why you're not draining the compressor down...the 100ft of 3/8" hose. When you step up the piping you will be sandblasting much faster, yes it will draw more air, but your work will go much quicker.

 

[bad_idea]

Problem is, I will still need a hose to reach out into the yard where I sandblast. Figure I ought to step it up to a larger hose, or would a shorter 3/8 hose work?

 

[Jswain]

Problem is, I will still need a hose to reach out into the yard where I sandblast. Figure I ought to step it up to a larger hose, or would a shorter 3/8 hose work?

Hardline as much as you can in the shop, then as short of a 1/2" hose as you can to reach.

 

[Shoreline_]

It seems its just gonna be 1 or 2 cfm. If you're running on the ragged edge like that why not bump up to a 7.5hp pump and motor? Or a 2nd 5hp and use it under high demand?

 

[bad_idea]

It seems its just gonna be 1 or 2 cfm. If you're running on the ragged edge like that why not bump up to a 7.5hp pump and motor? Or a 2nd 5hp and use it under high demand?

I am out to optimize the setup I have. I do not sand blast enough to invest that kind of coin.

 

[Jswain]

The beauty of the two stage compressor is storing the air under higher pressures than you are using. If you start with 160-175psi, and you are blasting at 70-80psj you have a large head start if your pump is outputting slightly less then you are consuming. (As long as your airlines are up to size and do not have a large pressure drop)

If you start with only 100psi in the tank, with 100ft of 3/8" hose, you're probably less then 70psi to begin with (pressure at tool) so as soon as you start blasting and the tank drops 20psi you're blasting less and less efficient as the minutes go by. Eventually to where the compressor will keep up, but only because you're actually blasting at 40-50psi. When your compressor is steadily always falling behind it seems to produce more moisture in the lines as well.

With a 2 stage you might have a 20-30 minute window where your tank pressure will remain above what you're blasting. In that 20-30 minutes you will get a lot of blasting done, maybe even the full pot. Convenient because then when you stop to refill so does your compressor.

There is a big misconception about "my 10cfm compressor keeps up sandblasting just fine". Yes, but you're feeding it with 50ft of 1/4" hose, or using a nozzle so small it plugs up every 20 seconds and have to stop to unblock it for 10 minutes.

To feed a sandblaster use 1/2" line and as short as possible/hardline as much as you can. Keep the line pressure high and regulate back to your blasting pressure with a regulator on the pot/cabinet.

 

[Shoreline_]

I am out to optimize the setup I have. I do not sand blast enough to invest that kind of coin

Overspeed the pump. Run the motor into the service factor. Run it full current into the service factor at 100 psi. It's a quincy qr it can handle it.

 

[Doubled33]

I have a 325 pressure lube running off of a 5HP motor. I use my cabinet at around 90 PSI. It does a good job keeping up, and if I stop for less than a minute it will catch up and cut off.

I ran a few calcs on tank time to fill and pressure and got over 23 cfm but that in its self seems off. There was a post on here some time ago talking about HP and maximum CFM and the science behind it. As I recall 5 HP does not get you 20 plus CFM.

My pump is set up per the guideline's of pulley sizes to deliver close to 18 CFM.