[TheForge] air compressors, CFM, and psig

[Craig Schaefer]

I respectfully disagree.   You don't know if the compressor is sized right 
because you can't quantify the work you're going to do with it.   Or at 
least I haven't seen that addressed.
A single 7.5hp single stage compressor is all I need to do work in my 
garage, one person using sanders, impact wrenches or paint guns.   Yours 
will be different based on how many simultaneous users of CFM you have. 
Unless you value your time very little, you have spent the $5000 worrying 
the situation.

CraigS
Gresham, OR
----- Original Message ----- 
From: "terry l. ridder" <terrylr at blauedonau.com>
To: "Craig Schaefer" <craig.schaefer at verizon.net>
Cc: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, May 06, 2009 7:28 PM
Subject: Re: [TheForge] air compressors, CFM, and psig


> hello;
>
>
> On Wed, 6 May 2009, Craig Schaefer wrote:
>
>> This all reminds me of going to work at my actual job.   All of this is a
>> remarkable treatise on the theory of work and how to accomplish it, but
>> there just isn't a damn thing actually getting done.
>>
>
> there is something actually getting done, it is helping with the research
> into which air compressor i am going to purchase and use in the new
> shop.  if i am going to spend $5,000.00+ usd on an air compressor i
> would like it to be the correct decision. understand the meaning of the
> 'cfm' specification is part of making a correct decision.
>
> SCFM (Standard Cubic Feet per Minute)
> http://en.wikipedia.org/wiki/SCFM
> <begin quote>
> CFM
>
> CFM is an often confusing term because it has no single definition that
> applies to all instances. In the most basic sense, CFM means cubic feet
> per minute. Unfortunately, air is a compressible gas. To further confuse
> the issue, a centrifugal fan is a constant CFM device or a constant
> volume device. This means that, provided the fan speed remains constant,
> a centrifugal fan will pump a constant volume of air. This is not the
> same as pumping a constant mass of air. Again, the fan will pump the
> same volume, though not mass, at any other air density. This means that
> the air velocity in a system is the same even though mass flow rate
> through the fan is not.
> <end   quote>
>
> this makes me think that the manufactuerers of air compressors are no
> better than a used car salesman.
>
>>
>> CraigS
>> Gresham, OR
>
> -- 
> terry l. ridder ><>
>