Convert scfm to cfm? my compressor puts out 4.9 scfm at 90psi; 7 scfm at 40 psi so how many cfm at 23 psi?

How would you know it isn't delivering the rated SCFM?
It is far from simple to measure this part of the specification.

While many manufacturers state the CFM in free air as a guide to choosing the right compressor and it is usually a theoretic calculated value using rpm and displacement.
It is interesting Kobalt has quoted an SCFM at 175 psi which is a very ambitious thing to do due to the many variable affecting compressor performance - temperature, humidity, supply current...

A 3.7 hp motor is similarly ambitious for a single phase supply (3-phase isn't stated). 2.5 hp is reckoned to be the maximum for a standard domestic supply and even then the high starting current can cause problems as well as when working hard a voltage drop on the supply will cause slow running. A short dedicated supply is preferable and for a 3 hp motor it is considered necessary.

I would say a short and really heavy dedicated supply is necessary for 3.7 hp and if any dimming or flickering of the lighting is taking place the motor will certainly be running at less than the rated speed and therefore a reduced air volume.

Use this method to determine the fill rate.http://www.ehow.com/how_5001852_calculate-cfm-air-compressor.html#page=1

The data provided did not provide start and stop pressure. The above method will get you there. Your cubic foot volume on the 50 liter tank is 1.7647 cubic feet to save you some calculations.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/john_28069c9efb56199d

For the Equation to follow the following definitions apply

S = scfm (the answer you want)
P = Barometric pressure in Pounds per square inch when you measured the cfm.
14.696 = standard barometric pressure at sea level

So:

S = P/14.73 x cfm

Example: Denver

Barometric Pressure 11.50 psi
cfm = 5400

S = 11.5 / 14.696 x 5400 = 4225.6 scfm

There was a lot of debate in the Natural gas industry years ago about the Standard barometric pressure value. Some Companies used 14.69 psi and others used 14.73 psi.

If you use natural gas to heat your home this is the same equation used by the gas company to correct for altitude on your bill.

The equation is derived from Boyles Law which is accurate at pressures close to atmospheric pressure.

Hi and welcome to FixYa, I am Kelly.

Air Tool consumptions are based on 15 seconds per minute (25%) of tool use.

Usage rates refer to the total time that air is flowing through the tool. If your applications result in more extensive usage, calculate air tool requirements as

follows.

(25%) 15 seconds = rated scfm x 1

(50%) 30 seconds = rated scfm x 2

(75%) 45 seconds = rated scfm x 3
(100%) 60 seconds = rated scfm x 4

Your impact wrench is rated a 8 CFM Cubic Feet Per Minute Usage

SCFM is Standard Cubic Feet per Minute (pre-compressed air volume)

I would be more concerned that the plumbing from the compressor tank could support the 8 CFM required by the 1/2" Impact. Remember the Air compressor will recover the pressure loss regardless of size. The only problem your going to have for "small jobs" is if you use too small of an air line to supply the impact wrench you are not going to get the full torque that it will produce to the drive head. In other words... a 1/4" supply line or 1/4 fittings anywhere in the system just isn't going to cut it even at 120 PSI. If you have the patience... a 5 gallon tank compressor that has the output volume required should be all that you need. I have been a mechanic over 4 decades and rarely have to use a 1/2 in impact for very long. Examples of 1/2" vs 3/8" useage. Wheel nuts, crankshaft pulley center bolt, some starters, steering, suspension and rear end parts. Other than that a 3/8" Impact works great.

One other thing you can do if you have an Air-Peen portable tank (with added fittings) is to add that in line with your output hose when your using the impact wrench so that you have longer use times.

I know this does not answer your what SCFM compressor is required question but it will resolve your needs. I just can't see telling someone that is a "small jobs" user to buy a larger compressor when really all they need is more volume for a brief period of time. The re-plumbed 1/2 inch output / in-line Air-Peen tank is a much cheaper and reasonable work around and you can disconnect that tank when your not using the impact wrench.
Lastly... if your inpact wrench has a SMALL male air fitting everything above will be a waste of time. You have to get that volume into the tool without restriction so that the rool will work properly for you.

Thanks for choosing FixYa.
Kelly

I have a Mastercraft 820218.
Specs are: 2 peak HP 5 Gallon tank 5.0 cfl @ 40 psi 4.0 cfm @90 psi max pressure 125 psi

THE PSI RATING IS 70-100PSI. I WASN'T ABLE TO FIND THE SCFM AT THEIR WEBSITE. NO MANUALS AVAILABLE AS OF YET.

You can get the manual for model 41214 from my dropbox area:

http://dl.dropbox.com/u/54567653/husky_aircompressor_model_41214.pdf

BTW, if you find this manual helpful consider installing dropbox using this link (full disclosure -- I do get about 0.2 GB freespace from dropbox if you install using this link):
http://db.tt/vQycqXIW

Thanks,K

You need to look at the tool cfm requirements because they are posted on the package or usually in the ads. Your compressor will run the sander, just how long at a time will depend upon your tool's cfm. Rick

One of the factors used to designate compressor power is motor horsepower. However, this isn't the best indicator. You really need to know the amount of air the compressor can deliver at a specific pressure. The rate at which a compressor can deliver a volume of air is noted in cubic feet per minute (cfm). Because atmospheric pressure plays a role in how fast air moves into the cylinder, cfm will vary with atmospheric pressure. It also varies with the temperature and humidity of the air. To set an even playing field, makers calculate standard cubic feet per minute (scfm) as cfm at sea level with 68 degrees F air at 36% relative humidity. Scfm ratings are given at a specific pressure–3.0 scfm at 90 psi, for example. If you reduce pressure, scfm goes up, and vice versa. You also may run across a rating called displacement cfm. This figure is the product of cylinder displacement and motor rpm. In comparison with scfm, it provides an index of compressor pump efficiency. The cfm and psi ratings are important because they indicate the tools that a particular compressor can drive. When choosing a compressor, make sure it can supply the amount of air and the pressure that your tools need.

One of the factors used to designate compressor power is motor horsepower. However, this isn't the best indicator. You really need to know the amount of air the compressor can deliver at a specific pressure. The rate at which a compressor can deliver a volume of air is noted in cubic feet per minute (cfm). Because atmospheric pressure plays a role in how fast air moves into the cylinder, cfm will vary with atmospheric pressure. It also varies with the temperature and humidity of the air. To set an even playing field, makers calculate standard cubic feet per minute (scfm) as cfm at sea level with 68 degrees F air at 36% relative humidity. Scfm ratings are given at a specific pressure–3.0 scfm at 90 psi, for example. If you reduce pressure, scfm goes up, and vice versa. You also may run across a rating called displacement cfm. This figure is the product of cylinder displacement and motor rpm. In comparison with scfm, it provides an index of compressor pump efficiency. The cfm and psi ratings are important because they indicate the tools that a particular compressor can drive. When choosing a compressor, make sure it can supply the amount of air and the pressure that your tools need.