[AT] Pressure drop?

Wed Jan 30 06:58:56 PST 2008

Charlie,

I don't mind plunging in because I'm not hindered by advanced formal
education beyond high school where I graduated nearly 56 years ago.  I've
been trying to learn ever since.  

There is a flow issue with electricity but it doesn't compare directly to
turbulence.  It's dependent on frequency and is called skin effect.  The
higher the frequency the greater the tendency for the flow to be nearer the
outside (skin). 

George 

> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com [mailto:at-
> bounces at lists.antique-tractor.com] On Behalf Of charlie hill
> Sent: Wednesday, January 30, 2008 8:57 AM
> To: Antique tractor email discussion group
> Subject: Re: [AT] Pressure drop?
> 
> I hate to get into this because I don't remember much about the little bit
> I
> used to know on this subject BUT.  There are a couple more variables that
> need consideration.  One is the capacity of Farmers compressor.  If it is
> marginal (say it only puts out 10 CFM) I think you can expect a larger
> pressure drop than the charts might indicate because the compressor won't
> be
> able to keep up against the head.
> The other is the issue of laminar vs turbulent flow.  Obviously in this
> case
> with 10 CFM flowing through a 1/2 inch line we are talking about turbulent
> flow and that's probably what the charts are derived for.  I don't think
> there is a flow type issue in electricity and now I'm really talking about
> something I don't know anything about so I'll shut up.  Not trying to
> start
> an argument.  Just food for discussion.
> 
> Charlie
> ----- Original Message -----
> From: "Dudley Rupert" <drupert at premier1.net>
> To: "Antique tractor email discussion group" <at at lists.antique-
> tractor.com>
> Sent: Wednesday, January 30, 2008 12:50 AM
> Subject: Re: [AT] Pressure drop?
> 
> 
> > 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
> >> _______________________________________________
> >> AT mailing list
> >> http://www.antique-tractor.com/mailman/listinfo/at
> >>
> >
> > _______________________________________________
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> >
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> >
> >
> > --
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