Repowering a compressor

This is in regards to my compressor

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It is currently powered by a 3 HP Baldor motor. I came across a 5 HP baldor motor, very similar, just a little bigger. I would like to know what would happen if I tried to run the pump faster with a bigger motor. Would it overheat or otherwise destroy itself from running 2/3 faster?

i
Reply to
Ignoramus7016
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Just because the motor is bigger doesn't mean that it turns faster.

Reply to
Dave Lyon

What is the actual spec'd RPM of each motor? The 5 hp could spin faster, slower, or the same, with the same 5 hp.

Dave

Reply to
spamTHISbrp

Most 60 Hz integral-HP induction motors, regardless of power rating, run at either a bit less than 1800 RPM or a bit less than 3600 RPM. If you don't change the pulley sizes, the compressor won't know the difference. The bigger motor will run cooler, but may have higher starting surge current.

If you do change the pulleys, then the question becomes one of "why shouldn't I exceed the ratings of the pump?" It's your pump!

Reply to
Don Foreman

wrote: The 5 hp could spin faster, slower, or the same, with the same 5 hp. ^^^^^^^^^^^^^^^^ Let's assume that Iggy ain't stupid. Most compressors are belt driven. A 5 HP motor would be able to drive the compressor with a larger pulley, thus giving him more volume. Since it is common to air-cool the compressor with blades that are integral with the driven pulley, the extra air flow mitght take care of it.

I suggest you take it in steps--maybe bring the speed up half way, and see how hot the compressor gets.

Reply to
Leo Lichtman

I think Iggy's smart enough to plan on a bigger drive pulley. He just assumed he didn't need to spell out every detail

Reply to
Rex

It has the same RPM, but I could fit a bigger pulley to the motor so that the pump spins faster. The question is, would spinning faster be damaging to the pump.

i
Reply to
Ignoramus7016

Well, yes, I would change a pulley to a bigger pulley.

That is exactly my question. Are those pumps made so that they cannot be run faster than at my given RPM.

i
Reply to
Ignoramus7016

Leo, yes, I would change the motor and install a bigger pulley, yes.

My main concern is just what would happen to a pump if it is being turned at a 60% faster rate. Would it withstand greater mechanical stresses? Would it heat up beyond the ability of the driven pulley to cool it? Obviously, one compressor head may be made differently from another, etc, I was just hoping that some people have some similar experiences. I will try calling a Curtis dealer, as well, if I hear that at least some people tried that with some pumps and succeeded..

Reply to
Ignoramus7016

Probably not.

But since the data plate on the compressor states explicitly "Do not run less than 150 rpm or above max as stipulated", you need to figure out what the rated rpm is.

Get a hold of Curtis and find out. It looks like a decent compressor, and is probably running at less than max capacity. This is done for a few reasons:

1) Makes it easy to offer a "better" model. 2) It's quieter 3) With proper maintenance it will cause less wear/tear and should last longer.

If you speed it up, it will run hotter. Will it be too hot? Depends. If you speed it up, it will be louder. Will it be too loud, that's up to you.

You will get more air, but do you really need it? What sort of duty cycle are you running now?

JW

Reply to
jw

JW, thank you, I will get a hold of Curtis and will try to find out. I do not need more air now, but I might if I get a sand blaster. All I use it for, now, is air tools.

i
Reply to
Ignoramus7016

I have done this. Changing the motor involves obtaining a new pulley (maybe not at all cheap, maybe 2-part) and buying new belts (get 'em matched, those might not be cheap at all either). Then you have to realize that you're now dealing with more power. Uh-oh, that size 1 mag switch is now too small. New mag switch

  • enclosure + heaters = way more bucks.

Just think it all the way through before you jump.

I have given up any remote idea of owning a compressor big enough to sandblast with. If I need to run a jackhammer or sandblast, I'll rent a compressor on a trailer.

GWE

Reply to
Grant Erwin

"Ignoramus7016" wrote: (clip) I do not need more air now, but I might if I get a sand blaster. (clip) ^^^^^^^^^^^^^^^^^ You could keep two pulleys and belts on hand, and up the speed for sandblasting only.

Then again, if you leave the biger drive pulley on with the air tools, the duty cycle for the compressor will be lower, so you might break even.

Reply to
Leo Lichtman

Grant... Thanks... I have size 1 and 2 starters... in fact a little too many... (shameless plug) But you are right, it could be a bigger project than I think, esp. if the belt guard does not let me get a bigger pulley etc.

i
Reply to
Ignoramus7016

You're obviously right.

I guess I'm used to dealing with people that don't understand mechanical things. I wasn't trying to be offensive.

Reply to
Dave Lyon

I took no offense Dave.

i
Reply to
Ignoramus7016

it will probably be ok for blasting as is. i use an ingersoll-rand 3hp

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continuous duty compressor for my blasting. it depends upon the gun you're using, and the orifice in the gun. a smaller orifice will not use as much air as a larger one.

the hp isn't the determining factor; it's the cfm at X psi that is required for a task. your blasting gun will have a minimum spec.

regards, charlie

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Reply to
charlie

Well considering Iggy's handle, it's understandable :)

Reply to
Rex

Well, it all depends on what the manufacturer has determined is the max. The faster you spin it, the hotter the cylinders get. At some point, the air can't get out of the cylinders fast enough, and the pumping loss goes up, or the air can't get IN fast enough, and capacity declines. If the former, it is real hard on the compressor, if the latter, it is just inefficient. The manufacturer should have some specs somewhere, but it may take some digging if this model (or maker) is no longer made.

Most compressors have a min and max RPM spec. If it has leaf valves I'd be real cautious. With disc valves it is a little less of a worry.

Jon

Reply to
Jon Elson

Go to your local chinese tool emporium (northern, princess auto, etc) and look at their compressors. They will have 2 or 3 different capacities built around the same compressor head, with different motors and pulley sises. Generally compressor motors are 1750RPM and the compressors run around 750 RPM on the small motor and 1200 on the big motor. Many small compressors run direct drive at 3475. I run my compressor on 1HP - a friend has the same unit running on 5HP

- and his pulley isabout 3 times the size of mine. His starts i winter cold - mine needs to be warmed up so I'll likely get a smaller pulley -----.

Reply to
clare at snyder.on.ca

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