duty cycle of air compressor

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Vavet

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I have an oil lubricated Speedaire (house brand of Grainger) air compressor in my lab at work. It seems like the head gets quite hot, so I timed the on and off periods and calculated the duty cycle.
on time = 2:32 ~ 2.5 minutes
off time = 5:23 ~ 5.4 minutes
total cycle time 2.5 + 5.4 = 7.9 minutes
duty cycle = on time / total cycle time
duty cycle = 2.5 / 7.9 = 31.6%

Then I compared that to the owner's manual - oh wait, it's not in there. Hmmm...I wonder what it is.

So I looked at other manufacturers to find their duty cycle on similar configuration compressors. Hmm, it's not there either.

Does anyone have any ideas on what a typical duty cycle for an oil-type single state air compressor is?
Or perhaps a more appropriate question is : do you know what a reasonable temperature for the compressor head is?
 
Reasonable temperatures are roughly 150F (about hot enough to cause 1st degree burn on your skin).

Reasonable duty cycles vary quite a bit but I could see the range for low end equipment being about 25% followed by 50% for mid-tier equipment and of course 100% for industrial rated equipment.

Ray



Vavet said:
I have an oil lubricated Speedaire (house brand of Grainger) air compressor in my lab at work. It seems like the head gets quite hot, so I timed the on and off periods and calculated the duty cycle.
on time = 2:32 ~ 2.5 minutes
off time = 5:23 ~ 5.4 minutes
total cycle time 2.5 + 5.4 = 7.9 minutes
duty cycle = on time / total cycle time
duty cycle = 2.5 / 7.9 = 31.6%

Then I compared that to the owner's manual - oh wait, it's not in there. Hmmm...I wonder what it is.

So I looked at other manufacturers to find their duty cycle on similar configuration compressors. Hmm, it's not there either.

Does anyone have any ideas on what a typical duty cycle for an oil-type single state air compressor is?
Or perhaps a more appropriate question is : do you know what a reasonable temperature for the compressor head is?
Click to expand...
 
I was told many years ago that "if you can touch it for a couple seconds without screaming in pain it was about or less than 150F"
just my old humble opinion
 
The motor will probably be rated 115% duty cycle, so no worries there. A good amount of that heat you are feeling is not from friction, it is the heat of compression of the air. Assuming that the compression is adiabatic (no heat loss), which is the closest to what an air compressor is doing, given a 75 degree inlet temperature, the outlet will be about 145 degrees. Higher inlet temperatures mean higher compressed temperatures, plus there is a contribution by friction. I expect the compressors were designed to run between 150 and 200 degrees. Unless there is smoke coming out of it, I wouldn't worry too much about it, given your low duty cycle.
 
My father gave me a Speed Air when I was around 16 back in the 70s. I used that compressor to paint at least 15 cars and trucks. I would also use it for sand the bodies. That thing would run for hour a day. It would get hot as you are saying but never quit. About 10 years ago I got another in trade for wiring a pump circuit for an old friend. He thought the motor might be bad. I cleaned it and gave it to my son who still uses it for home projects and in his garage. It also get hot but has lasted real well.
I believe yours gets no hotter than any other high RPM (3450 motor) oil lubed compressor of its size.Big dollar compressors spin a lot slower so they run cooler. 1725 RPM. And by the way my first one was cranked up to 135 LBS shut off. These are SUPER compressors for the money.
Ron
 
A buddy tank reduces wear and tear on a compressor. It's just an empty tank for more air storage capacity. I don't know the why's and wherefor's, but an airbubble placed in line before the hose being used makes life better on the guy needing air and the compressor too.
 
A good brand name (like yours) permanent installation oil lubricated air compressor pump is designed to run a lot. I wouldn't go so far as to say 24/7, but they should run a good work day with no problems. As long as you have good clean oil in them, they should last a long time. I agree with cjtoombs about the air being compressed as the source of most of the heat, with friction adding just a little more. You could put a fan on the cylinder head, but I don't think it would really accomplish anything. I think Speedaire uses cast iron pumps, so 150-200 degrees is still way below what a normal cast iron (or even aluminum) car engine runs at. I'm by no means an expert, but I've never seen a duty cycle on an air compressor.

GG
 
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