# Air Compressor Capacity in CFM

1. Oct 18, 2011

### dtaftm

Hi,

First time user here.

I was hoping someone could help me calculate the CFM of air needed for an Air Compressor to air-clean 16 tubes. The Compressor is connected to a header that has 116 PSI of Pressure. The header is connected to 16 thin pipes that have nozzle tips with a 1.5 inch diameter. The nozzles release air in sequence, one at a time. We are counting on 220 liters per valve with 3 releases per hour. In other words 660 liters per hour per valve.

Thank you

Last edited: Oct 18, 2011
2. Oct 18, 2011

### edgepflow

I would do the following:

(a) Figure out the volume of each tube.
(b) Divide the volume in Part (a) by 1/2 second. This will be your actual flow rate per tube.
(c) Convert your flow rate in part (b) to standard conditions.
(d) Establish the time interval between each tube firing.
(f) Multiply the volume in Step (a) by 16.
(g) Multiply the time interval in Step (d) by 16.
(h) Divide the volume in Step (f) by the time in Step (g).
(i) Convert your flow rate in part (h) to standard conditions.
(j) Size your compressor for the larger flow rate from Step (c) or (i). Include a safety factor between 1.25 to 1.75 depending on how confident you are in your input.

3. Oct 18, 2011

### dtaftm

Thanks Edge,
The problem is that I don´t have the dimensions of the tubes yet.
Here´s the situation. I need to purchase an Air Compressor to supply the air to the new system that we´re going to implement. I know that we will need to supply 10,560 liters/hr at 116 PSI of pressure. Can I calculate the capacity of the air compressor that I will need to supply that much air to the system with just that info. I´m getting 6.21 CFM which seems way to little.
Thanks

4. Oct 18, 2011

### edgepflow

Your 10,560 liter/hr = 6.21 is your "actual" flow rate. Compressors will be rated for "standard" flow rate. You can convert your actual flow to standard with:

Standard Flow Rate = $\frac{T_{STD}}{T_{ACT}}$$\frac{P_{ACT}}{T_{STD}}$ Actual Flow Rate

T_STD = 60 degF
P_STD = 14.7 psia
P_ACT = (116 + 14.7) psia
T_ACT = your actual flowing temperature

5. Oct 19, 2011

### dtaftm

Great, Thanks for your help Edge.

6. Oct 20, 2011

### MikeTheLost

Many compressors don't like a high duty cycle, something like 40% comes to mind. Too many starts per hour should also be avoided, so be sure to size your storage tank to accommodate both factors depending on the motor and compressor selected.

7. Oct 20, 2011

Thanks Mike