CFM vs FAD CFM

[mark328]

Thanks for the add. Long term lurker.

Why do compressor manufacturers only mention their products CFM and not FAD CFM?

I am just switching from rattle cans to home auto touch ups/smart repairs and finding it difficult to match a HVLP gun to a compressor. The gun manufacturers mention 'air consumption required' but does this relate to the compressors CFM or FAD CFM?

I bought a 50l 11.4cfm compressor yesterday for £149.99 based on its 11.4 CFM, now realised number is worthless and its 4.4 FAD CFM is poor.

 

[Shox Dr]

Its a bigger number simple as that. As you have found out its usually around 35% less than the stated CFM. The one you bought is Pish poor

 

[mark328]

Its a bigger number simple as that. As you have found out its usually around 35% less than the stated CFM. The one you bought is Pish poor

Damn it, 4.4 FAD, only 35% of the 11.4 CFM. Definitely poor, thankfully its sealed and have the receipt

 

[Shox Dr]

and welcome to the forum

 

[mark328]

and welcome to the forum

Thank you!

 

[fizzy]

With new compressors more money usually equals more oomph!
Oh and size and weight.
Biggest you can run off a normal 13amp socket is 14CFM 3hp - belt drive are best as quieter than direct drive - but you are talking of £400 to £800.
Buy a used one or watch out for Machine Mart sales. Some Machine Marts have a returns section where you can get the odd bargain.

 

[MetalMonkey]

Why do compressor manufacturers only mention their products CFM and not FAD CFM?

Decent compressors should be rated for both, and will state at what pressure they will provide the FAD.

 

[mark328]

With new compressors more money usually equals more oomph!
Oh and size and weight.
Biggest you can run off a normal 13amp socket is 14CFM 3hp - belt drive are best as quieter than direct drive - but you are talking of £400 to £800.
Buy a used one or watch out for Machine Mart sales. Some Machine Marts have a returns section where you can get the odd bargain.

I thought I had a right bargain yesterday on the compressor (was online & ebay for £300+) for £150. Local motor factors so will either get refund or store credit

 

[fizzy]

It may do the job you want. I am no expert but smaller spray guns don't use that much - it is air tools you will struggle with more.

 

[mark328]

It may do the job you want. I am no expert but smaller spray guns don't use that much - it is air tools you will struggle with more.

I only wanted it for small smart repairs with a HVLP mini gun

 

[fizzy]

I only wanted it for small smart repairs with a HVLP mini gun

I am sure someone else can answer better than me but I would have thought it would cope with that.

 

[tom2207]

Compressors are one of those things you always buy twice the size you think you will need , air tools are wicked on air , but once you have it you wouldnt be without ,,
Welcome to the forum.

 

[addjunkie]

I only wanted it for small smart repairs with a HVLP mini gun

HVLP……4.4 cfm isnt going to cut the mustard. Even a touch up gun will ve about 4.5 cfm

 

[not done it yet]

Its a bigger number simple as that. As you have found out its usually around 35% less than the stated CFM. The one you bought is Pish poor

And don’t forget the air tools always quote the lowest air usage! Think about it - the users of compressed air have to quote as FAD, because that is all they know about how it was compressed! They should also quote the pressure required, too.

 

[mark328]

Makes you wonder what 4.4 FAD COULD actually run lol

 

[Turbo]

Welcome to the forum!

You are a bit mixed up in your terminology.

FAD stands for Fixed Air Displacement and is is the volume of air the compressor piston(s) displace on one full stroke of the pump. This will always be the higher figure given but it is only a theoretical figure & will never be reached.

CFM stands for Cubic Feet Per Minute & is the actual volume of air the compressor produces under working conditions. This is the figure you need to spec your comp.

 

[Jack Ryan]

You are a bit mixed up in your terminology.

FAD stands for Fixed Air Displacement and is is the volume of air the compressor piston(s) displace on one full stroke of the pump. This will always be the higher figure given but it is only a theoretical figure & will never be reached.

FAD is Free Air Delivery which is the flow, at a specified pressure, referred to the air intake - also under specific atmospheric conditions.

It is not the compressor's actual displacement.

CFM stands for Cubic Feet Per Minute & is the actual volume of air the compressor produces under working conditions. This is the figure you need to spec your comp.

You can't specify a compressor based on CFM alone, like FAD, it has to be specified at a working pressure. Without the pressure, the flow is meaningless.

I think you don't get proper specifications and performance data for a compressor unless you are looking at industrial equipment. At the local tool shop you get decorative numeric sprinkles.

Some people use the engine power as an estimate but that is highly dependent upon efficiency. Sometimes there is no other choice.

There are many other variables that affect individual requirements as well.

Jack

 

[carbon]

its 4.4 FAD CFM is poor

How have you determined this value?

I only wanted it for small smart repairs with a HVLP mini gun

I have the older devilbiss sri pro and that requires 3.5cfm when fitted with a TS1 aircap

 

[mark328]

How have you determined this value?



I have the older devilbiss sri pro and that requires 3.5cfm when fitted with a TS1 aircap

It's on the box!

 

[Shox Dr]

It's on the box!

View attachment 394416

At least they are honest.