[AT] Pressure drop?

[Cecil Bearden]

Dudley Rupert wrote:
> The following site contains a table that will answer the question (assuming
> the table is correct) -
>
> http://www.engineeringtoolbox.com/compressed-air-pressure-loss-d_1014.html
>
> For example, it looks like for a 1/2" pipe with 10 SCFM of air flowing
> through it @100PSI the drop is 0.4 psi for every 100 feet of pipe.
>
> Like Dean said in a post a few minutes ago electricity and airflow behave a
> lot alike.  Voltage drop is the easier to calculate however.  For example,
> if you double the amount current through a wire you simply double the
> voltage drop between the ends of the wire (Ohms Law).  From the table above,
> however, it looks like air pressure drop in a pipe is more complicated to
> compute; that is, it cannot be computed by a simple (linear) expression of a
> couple of variables ... maybe with some regression analysis and fancy curve
> fitting one could come with a polynomial for computing air pressure drop.
>
> Dudley
> Snohomish, Washington
>
>
> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com
> [mailto:at-bounces at lists.antique-tractor.com]On Behalf Of
> rlgoss at insightbb.com
> Sent: Tuesday, January 29, 2008 7:16 PM
> To: Antique tractor email discussion group
> Subject: Re: [AT] Pressure drop?
>
> It's going to depend on the flow rate, Farmer.  If it's just a pressurized
> line, there is no pressure drop.  But if you want it to deliver 9 CFM at 90
> PSI, you may have trouble.  I don't have the formula with me for doing the
> calculation, but it shouldn't be difficult to find.  Try searching for "line
> loss."
>
> Larry
>
>
> ----- Original Message -----
> From: Francis Robinson <robinson at svs.net>
> Date: Tuesday, January 29, 2008 20:57
> Subject: [AT] Pressure drop?
> To: Antique tractor email discussion group <at at lists.antique-tractor.com>
>
>   
>> OK, who knows compressed air pressure drop off of the top of
>> your head?
>> :-)
>> I am going to run a compressed air line from one shop to the
>> other. It
>> will run inside of an underground conduit in 1/2" PEX tubing. It
>> will
>> basically have one fitting (full 1/2") at each end of the run.
>> The run will
>> be 250' long with no fittings at all in the line itself. If I
>> have 125 PSI
>> at one end what kind of drop can I expect at the other end? What
>> would it
>> be at 800'?
>> BTW, PEX is rated and recommended for compressed air. I was
>> reading the
>> print on the pipe today and for water what I have on hand at the
>> moment is
>> rated at 100 PSI at 180 degrees F. It will not get hard and
>> brittle and it
>> will not shatter on impact. It is cross linked polyethylene and
>> is not
>> affected by oil.
>> I am really in love with this stuff for water plumbing.
>>
>>
>>
>>
>>
>> --
>> "farmer"
>>
>>
>> Francis Robinson
>> Central Indiana, USA
>> Robinson at svs.net
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>>
>>     
>
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>   
Not wanting to sound like a Know-It-All, but I do have one of those 
Engineering Degrees in Agricultural Engineering from Oklahoma State...   
I would say that for the normal 4cfm at 90 psi requirement of most air 
tools, that Farmers 1/2 pex pipe would be purt near good enough.
Just my educated opinon.
Cecil in OKla