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air compressor flow rate. (FAD or Nm3/h) 1

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hassann

hassann

Civil/Environmental
May 7, 2018
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Hi ,
it might be a pretty basic question, but any help will be great. I'm trying to select an air compressor with capacity of 580 Nm3/h. I'm having a bit of difficulty finding the right decision to doing it. In manufacture catalogue data are based on FAD (free air delivery) and is 588. Is there any difference between FAD and nm3/h?
thanks,
 
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The difference is that the temperature and pressure associated with the two different volumetric flow rates are different, based on whether a defined T,P combination is used (i.e. Normal conditions) or the site specific conditions (i.e. Free air). Free air determination can also include other factors like accounting for inlet pressure loses. See the links below for more info. If you can, state your air requirements in mass flow terms so you can always check to an unvarying quantity.

 
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What is your definition of "normal" conditions?

Often 0C and 101625 qPa (1 atm).

FAD is a similar number and supposed to be back calculated from the air actually supplied at pressure so is supposed to take account of any losses. But if often at 20C.

Check the definition of FAD from the vendor.

So 588 FAD maybe a bit too close for comfort. [pre][/pre]

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Also: If you get a response it's polite to respond to it.
 
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Check the definition of FAD from the vendor.
Click to expand...
Bellow is vendor explanation that I need your help to undrestanding it. (if possible)

VENDOR
Note: The FAD flow is not greatly affected by inlet temperature as it is a volume flow rate;
however the mass rate of flow will alter.
 
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Ha!

What that means is that a the temp goes up the Sm3h or Nm3h goes down.

They are paying a bit fast and lose there IMO.

There's no point in having a FAD definition and then change it when they feel like it....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Technically they are correct in that the volume flow of air at the inlet, regardless of temperature or indeed pressure will remain more or less the same.

But if you then convert that higher temperature flow to a standard volume, be it scm or ncm, it would reduce in volume flow.

Especially as you say, ncm is at 0C, there isn't enough margin between what you want (580) and what the compressor can deliver (588).

Also you haven't said what is your elevation and max air temperature? Unless it's sea level and in the artic, your nm3/h could be 20-30% less than you want.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Anyway, have we answered your question?

Basically I think FAD of 588m3/h won't get within 10% of your 580 nm3/h.

But make sure your 580 is really needed and not a very occasional one off. Oversizing air compressors is not good for anyone and neither is undersizing your air tank...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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hassann said:
one of the best manufacturer in the word. I am not sure i have permit to say the name, but what is your point about this question?
Click to expand...

I'm sure they would enjoy the free advertising. Some manufacturers I have experience with have a well defined FAD. If your supplier was one that I knew, I was going to provide that information. That's all.

Good Luck,
Latexman

 
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pierreick (Chemical)
Click to expand...
thanks for sharing that good file.
that file had an example about converting SCFM to ACFM, but i did not see how to convert scfm or acfm to fad.
For that especial example for 1000 scfm calculated acfm is 1062,and up to now i dont know what is fad when scfm is 1000?(considering all conditions same as humidity,ambient temp/temp, ... are the same as example)
 
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hassann said:
Up to know I havenot understood 100 percent the concept and definition of fad.what is the relation between fad and scfm (or ncfm)?
Click to expand...

If you would answer our questions directly, without questioning our questions, you would have had more useful information by now.

hassann said:
Are you saying that FAD has not a global definition and each manufacture has own definition?
Click to expand...

No, I did not say that. I have FAD information on a few vendors. I do not know about all vendors.

Good Luck,
Latexman

 
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There you go again. You still did not answer, what I thought was, a straightforward question, so I could help. I think you may be a troll.

Good Luck,
Latexman

 
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It is unfortunately a bit of a moving feast but What they do when they say FAD is that the back calculate how muc air thet have taken into the compressore at sea level and 20C to create the air that they are actually delivering.

So E.g. the Deliver say 100 actual m3 of compressad air at 10 barg (11 bara) at say 50C, they work out how much air that is at their definition of "Free air" that they actually took in.

From eng tool box
"FAD (Free Air Delivery) (f.a.d) is the actual quantity of compressed air converted back to the inlet conditions of the compressor. The units for FAD are CFM in the imperial system and l/min in the SI system. The units are in general measured according the ambient inlet standard conditions ISO 1217: Ambient temperature = 20oC,"

From Pierres link

"FREE AIR DELIVERY (FAD)
Measured in CFM (Cubic feet per minute) this is the amount of compressed air converted back to the
actual inlet (free air) conditions before it was compressed. In other words, the volume of air, which is
drawn in from the atmosphere by the compressor, then compressed and delivered at a specific pressure."

So FAD is 1 atm (101625 Pa) @ 20C
Sm3 is normally 101625Pa @ 15C
Nm3 is usually 101625Pa @ 0C

That's why that response you got from the vendor was rather odd as temperature matters.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Don't think it matters for volume. Matters when it comes to the dryer.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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