Running out of breath!

[norsa]

Trying to get a hold of my CFM's. Coming out of my own business using a 3ph compressor, it was no problem and i seem to recall it was calculated that i needed 21 CFM (free air) to breathe and spray. Now im at my home garage and have a single phase quoting 14cfm (manufacturer) my mask says it wants 6. Plugged in, the compressor just about struggles to maintain the 70psi that the mask needs. So. i obviously need a second compressor when it comes to spraying the escort in a year or so. Is there some sort of calculation to sort out sufficient free air??
Nick

 

[octo0072000]

what you are looking for is FAD

FAD stands for Free Air Delivery which indicates the compressors capacity, it normally described in: L/Sec, m3/min or cfm. Quote: The capacity of a compressor is the full rated volume of flow of gas compressed and delivered under conditions of total temperature, total pressure, and composition prevailing at the compressor inlet. It sometimes means actual flow rate, rather than rated volume of flow. This is also called free air delivery (FAD) i.e. air at atmospheric conditions at any specific location. This term does not mean air delivered under identical or standard conditions because the altitude, barometer, and temperature may vary at different localities and at different times.
Read more: http://wiki.answers.com/Q/What_is_fad_in_compressor#ixzz277fLRIR3

 

[eil]

Two 14CFM compressors will give you about 19 ish CFM free air, it depends on your gun requirements if it will be enough, you have to add up the requirements of the gun and mask. As you say 21 CFM would be ideal but you could get away with less, adding an extra receiver would help capacity but obviously take more time to fill.
Rule of thumb knock off a third of the compressor displacement or 3 and a bit CFM per horse power.

 

[norsa]

thats the sort of thing i was looking for. thanks

 

[Chipper]

I've got 2x 3hps with approx 18-19cfm FAD @ 100psi, it copes fine with my mask and an HVLP gun which wants about 10-11cfm I think. I run the mask at about 55 psi, think minimum is 50; 70 sounds on the high side maybe? But specs is specs.

 

[norsa]

thanks chipper. mask is from my pro days in the 90s so different requirements probably. I will probably buy a second 3hp and flog it when ive done the job. got to be cheaper than keep hiring one for the various stages of paint. I want to run 1 line into the boothe so if i couple the two units with say a q/r Y piece pre water trap/filter would it work?

 

[norsa]

the gun by the way is a circa 1985 sagola suction feed. Beautifully balanced and of its era very expensive top gun. Never enquired about cfm requirement when i got it. Never did and dont suppose i ever will hvlp.

 

[Chipper]

I made a 2-1 effort out of some steel tube bent up, one leg goes into one comp tank directly, and the other has a short length of hose. Thinking to allow for vibes and a comp poss deciding to walk about a little bit.

Before this I had joined comps with a shop-bought y-piece thing. The PCD connector specs say they pass 40cfm-ish at 100psi, so although the holes look pretty small, it should be plenty if that's right. And it did seem OK, but one of those comps was a little one.

I've heard of Sagola but never seen one. The Iwata does make less overspray than my JGA but it took me a fair time getting used to it. Probably still prefer the JGA really. Think both are better and will outlast me anyways!

 

[drjim]

This has me thinking that what is needed is a forum lending library type setup, for instance I currently own two Wolf 2.5 hp comps that are sitting in my/my Dad's garages doing nowt, if somebody needed a comp for a job I'd be happy to lend one out.

Heads off to suggestions section.

Jim

 

[eil]

thanks chipper. mask is from my pro days in the 90s so different requirements probably. I will probably buy a second 3hp and flog it when ive done the job. got to be cheaper than keep hiring one for the various stages of paint. I want to run 1 line into the boothe so if i couple the two units with say a q/r Y piece pre water trap/filter would it work?

What bore and length airline were you thinking of using.

 

[norsa]

Not really considered that yet but probably 10 metres of whatever the largest bore available for q/r