Compressor cfm calculations

[drivewasher]

My 50l fiac miami compressor can't keep up with a brand new air ratchet (not a cheapo one) tool should consume 4 ltrs a min..

The cfm of compressor is 13 cfm min ACTUAL FAD is or should is 8.66 cfmmin. so compressor should at least keep up with the ratchet

So I emptied the 50 ltr tank and timed it to fill up to 145 psi and it took 3.5 mins, can anyone who attended school on the day we did maths work out if thats about right.

Also to get the line pressure at 90 psi when running tool the regulated pressure needs to be about 120 psi when not running tool in order to get it at 90 psi when it's running, but as the tank soon empties then the gauge will continue to fall along with the emptying of the tank

I blocked the inlets off to the cylynders one at a time and repeated test both cyls took about the same time to getup to 100 psi.

I need this comp working as I'm opening a tyre bay next week! Hoping this comp will do for a few months

 

[rtbcomp]

This is a minefield.

The delivered cfm figure is pretty meaningless unless they state at what pressure, for a given amount of air (mass) the cfm (volume/time) will decrease as the pressure increases, because the air is compressed (!)

From what I can find your compressor is 3hp 13 cfm (not litres/min).

https://wsdgroup.co.uk/comersus_viewItem.asp?idProduct=2229

Are you driving a ratchet or an impact driver? (tyre bay reference), an impact driver will use much more air.

Also for a tyre bay you want to reduce the length of pipe after the regulator as much as possible, use largest bore as possible and fit a 1/2 in regulator, if possible.

 

[drivewasher]

Sorry i have corrected my post. Itis CFM not ltrs per min. The only ltrs ref is the tank capacity.

Its an air ratchet not an impact gun. The impact gun seems to drain the tank much less thats why I bought a new good quality ratchet as the old one was not drving as it should the teeth on the wheel and pawls in the ratchet assy were a bit worn.
Tyre machine will get an unregulated supply of air, as it has a built on regulator and filter/oiler. It also has it's own air storage tank

 

[shenion]

50l = 1.76 cubic feet.

Fill to 145 PSI (10 bar or 10 atm) would eb 17.6 cf

So if it takes 3.5min to fill that is 17.6/3.5= 5 cfm

Mine takes near 6 minutes to fill to 120 PSI, then again it 230L tank Surprised that came out to near 13CFM. No bad for a a 15-year+ old compressor rated at 9.8CFM (all compressors here are rated in FAD, displacement is never even given.)

 

[eil]

Fiac site
http://www.fiac.it/famiglie_eng/Tecnici_12-27.asp
That compressor should cope with that ratchet by all accounts, is it another regulator problem I wonder.