We have a 50 liter tank that filled up to 4300 psi. in 7 min. how many scfm is my compressor putting out?

the air flow from a compressor is determined by the capacity of the pumping system
with a piston type compressor it is the bore by the stroke
in a diaphragm type is it is the diaphragm dia by the stroke
that is the maximum cubic feet of air a minute produced
pressure is the resistance to flow so regardless of the pressure or restriction it will only produce that set air flow at that rpms
do not confuse the flow with pressure as it works like this the greater the restriction the greater the pressure in reserve but the less flow in cubic ft per minute through the restriction
for example a compressor producing 10 cubic feet per minute does that with not restriction but with no pressure
at 25% restriction to air flow the pressure in the tank will now rise to say 25 psi and the flow from the restriction will drop to 8 cubic feet per minute
at 50% restriction the compressor is still putting out 10 cubic feet of air per minute but the tank pressure has risen to 50 psi and the flow from the restriction has dropped to 4 cubic ft per minute
go to the extreme end and the compressor is still producing 10 cubic ft of air per minute , the restriction now allows 100 psi in the tank but the low from the restriction has been reduced to 2 cubic ft per minute
the simple equation is pressure = flow X resistance

Hard to give an exact number, however, as pressure and temp of air increases, the scfm drops as you see in your numbers. With low pressure such as 0 thru 25 the temp of the air is also low/nominal thus the scfm will be very close to the actual cfm listed for the compressor pump.

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

You hit the nail on the head ... it is the regulator. What does it say on the side? What are they advertising the pressure and the SCFM? (Standard Cubic Feet (per) Minute)

The boss recently bought a Husky. It is rated at 6 SCFM @ 200 PSI (as I recall) ... Its regulator turns the machine off at 240 PSI then delivers the air through a regulator. In my case, I throttle it back to 150 PSI so I can get 80 PSI at the end of my 75 foot long hose. The machine comes on around 150 PSI (or of course any lower number) and takes for ever to build pressure back.

Should you change the regulator setting? Only if you want to diminish the performance of the compressor and possibly void the warranty. If yours doesn't have a regulator, I suggest you add one.

I hope you have found my comments helpful ...

Thanks for visiting today.

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

First check the condition of your air filter. Clean or replace as necessary.

Second time how long it takes for the compressor to build from 0-125 psi. If you have the 15gallon tank and it takes more than 3 or 4 min to build up then you have valve problems. If you have the 27 gallon tank it shouldn't take more than 7 min to build up.

If your pump up times are ok then you need to look at the duty cycle. Compressors such as yours should not be on more than 50% of the time. So if you use the compressor for 2 hours of work it should not be pumping for more than 1 hour of the time.

If your pump is working more than 50% or pumping continuously then you need a bigger compressor for your tasks.

The only other factor to consider is the room temperature. If the room where the compressor is is too hot it only magnifies the problem.

Hope that helps
under_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

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.