Compressor FAD

[Kittyhawk]

I am trying to understand if there is a relationship between FAD (free air delivery) and psi.
About to start the dreaded kitchen rebuild and I wish to spray a coating which should be applied by a compressor capable of delivering around FAD 280 l/min at 30psi.
My compressor details : 3hp, 50l tank, maximum air delivery 400l/min, FAD 200l/min @60psi. Does my required lesser 30 psi mean more FAD or is that just wishful thinking?

 

[Fitzroy]

It’s not going to help you. The FAD is at atmospheric conditions, think of it as the air drawn into the machine to be compressed. The machine then compresses it to its set pressure. Reciprocating compressors run at a set speed and compress the same amount of inlet air independent of the delivery pressure.

Where you will benefit is how long the compressor will run your tool for from the tank before it switches on. But it the tool uses more than the compressor can continually deliver the tank pressure will over time reduce and you’ll then have to wait for it to catch up.

Back of the *** packet calc for a 50l tank running at 110psi you’ll get 1.5mins of continuous spraying before the tank hits 60psi. You’ll then have to wait 45seconds for the tank to recharge.

 

[Kittyhawk]

It’s not going to help you. The FAD is at atmospheric conditions, think of it as the air drawn into the machine to be compressed. The machine then compresses it to its set pressure. Reciprocating compressors run at a set speed and compress the same amount of inlet air independent of the delivery pressure.

Where you will benefit is how long the compressor will run your tool for from the tank before it switches on. But it the tool uses more than the compressor can continually deliver the tank pressure will over time reduce and you’ll then have to wait for it to catch up.

Back of the *** packet calc for a 50l tank running at 110psi you’ll get 1.5mins of continuous spraying before the tank hits 60psi. You’ll then have to wait 45seconds for the tank to recharge.

Thanks your reply and advice.
I should be ok. My spray gun is an old Star gravity feed with a 1.4mm nozzle and requires either 6cfm or 9cfm, depending on what brochure you read. The 200l/min that the compressor puts out equates to 7.1cfm. The paint is a very thin water based lacquer. I'm a novice at this.

 

[Kittyhawk]

Only spraying drawer fronts and cupboard doors, say two passes per drawer and 5 - 6 per door so I.5 minute spray time per item should be plenty.