Question about air flow around pump head

I recently purchased the portable 3 gallon 125PSI horizontal single tank model.


I ended up returning the first two because of leaks around the quick connect valve (1st one) and total pump failure (2nd one).

The third model does not leak around the quick connect however I can feel quite a bit of blowing air around the pump head.

The tank gets up to 100+PSI so I'm thinking this must be normal. I cannot see where the air is coming from exactly but it may be coming from two different locations - one around the oil filler and the other somewhere near the top of the head.

If the seals on the pump were leaking I would think the tank would never get to pressure. Am I correct here? Or should I just bring this back to Sears and pay for a better unit (>$200)? Thanks.

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Bill says...

Sounds like you have another lemon. Air should not be blowing around the pump head, at least, not unless it's fan cooled.

It were me, I'd take it back.

Cheers,

Bill


Comments for Question about air flow around pump head

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Nov 17, 2011
Feeling a little foolish
by: Anonymous

Your response was a little disheartening as I've noticed that most of the mid-range models at Sears use the exact same air pump head setup.

So I decided to remove the plastic cover that surrounds the pump head and motor to try and get a better look at where the leak might be coming from and to try and tighten the head bolts a bit.

I found out that the air flow I was getting is from the fan on the electric motor used to cool everything. Because of the plastic covering the air is blown around and over the pump head which explains why I could never see or hear a leak.

I checked the head bolts in case and one was a little loose so I tightened it.

Everything seems to be working now.

I figured I post this reply in case others make the same mistake I made. Thanks for all the help though.

___________________

Good on you, and thanks for the update.

B.

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Craftsman air compressor - what is the flow?

by Michele
(Calgary)

It's a 2hp,25gal tank with the piston head, we bought it between 1994- 1996, we need to know the scfm on it.






Bill answers...

Hi Michele...

The important piece of information that you have provided me to help determine the compressed air flow from your compressor is the HP of the motor.

It's generally understood that a compressor will generate about 4 CFM of compressed air at about 90 PSI for every horsepower of motor size. That's the norm for compressors over 10 HP in size.

For a 2 HP motor, it will be a little less, yet you should expect to generate between 5 and 8 CFM at 90 PSI from your compressor.

I can't be exact as different manufacturers have different efficiencies in their compressor pump design, and where you are in relation to sea level, the air temperature and the humidity of the ambient air all affect compressor production.

The important piece of information you didn't include in your question was...at what pressure?

The higher the compressed air pressure required, the less the flow that can be generated by a specific compressor. While yours may generate 5-8 CFM at 90 PSI, if you only require 40 PSI for example, the flow will increase.

I'm sure there is a formula that allows one to determine the flow rate change based on differing output pressures, but I don't have that. Can anyone else offer that for us and other visitors?

You might pop into your compressor store (big box store?) and look at the compressors on display. Find one with a 2 HP motor and see (they should show you on the tag) what the output flow is at 90 PSI and usually at 40 PSI too. That will give you a good indication of what you can expect on yours.

Thanks for writing in from Calgary.

Cheers,

Bill

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