# Size of compressor required to fill up tanks

by RUI MARCOS
(CAPE TOWN, SOUTH AFRICA)

I have a tank at one of my clients that I have to fill up to do a soap leak test. The tank has 960.000 lts capacity of capacity. What would be the capacity of the compressor in m3/min that I need to outsource to fill up such tank in 8 hours? Please provide me with the formula if possible.

Regards

### Comments for Size of compressor required to fill up tanks

 Jan 29, 2014 Filling a tank with a HUGE compressor by: Doug in s.d.ca "The compressor capacity is 6000 CFM at 8 bar! I hope it helps. The question is how many hours roughly would take to fill a tank of such capacity."(That's a ***really*** big compressor - but if you have one...)And that's different than what you asked...6000 CFM ~= 34,000 lpm (pressure capability of compressor is irrelevant for this case)" Once the tank has been filled up"This suggests the "tank" is collapsible/inflatable, and when it is inflated, it contains 960,000 litres?That is just normal air pressure - 1 bar, but zero bar on gauge, right? So, 960,000l / 34,000lpm = 28.2 minutes to initially fill/expand to 1 bar." I need to pressurized it to 0.2 bar (20 kpa). "So, 1.2 bar, or .2 bar gauge?" How long would then take to reach such pressure once the tank is full of air?"If you only need .2 bar above atmosphere, about another 6 mins to reach .2bar (gauge).

 Jan 28, 2014 960 M3 by: Anonymous The compressor capacity is 6000 CFM at 8 bar! I hope it helps. The question is how many hours roughly would take to fill a tank of such capacity. Once the tank has been filled up I need to pressurized it to 0.2 bar (20 kpa). How long would then take to reach such pressure once the tank is full of air?

 Jan 27, 2014 fill by: Doug in s.d.ca 960,000? nine hundred sixty thousand? What? Litres?To what pressure?Do the math.

## Calculating PSI CFM and capacity for moving falling object

by RedCap
(California)

First of all, congratulations on a most informative site !

I inherit a project that needs to move a falling object a certain distance with compressed air controlled by air valves. I am an electronic engineer and have no air flow background.
How do I calculate how much power, PSI I need for say 500gm objects falling from rest for 400mm before reaching the valve. The object must be moved for some 300mm out of it's falling path.
The objects is about 100mm x80mm in diameter.
The installed valves have a 2mm nozzle, and can move 300l/min air at 8 bar. I have a bank of ten valves next to each other, the nozzles are 10mm apart. Thus, 8 to 10 valves can be activated at the same time for moving a 100mm x80mm object.

The electronics can control the length of the activation time of the valves.
We would like to keep the valves but can change if that's what needs to be done.

Questions: 1. How do I calculate all the relevant air parameters. 2. Nozzle size, flow, psi, total cfm's. 3. Any available formulas you can point me to ? 4. Would I need to have a receptor/storage tank to manage a continuous flow of objects that can help
?
I think this can make out a nice, complete HOWTO once we solved all these issues.

Obviously we could go for the biggest airflow and pressure but would love to optimize air consumption and thus power / generator requirements.
I would appreciate your help or any one's that have this type of background and/or knowledge.
REDCAP ca.

## what is FAD in reciprocating compressor?

(pakistan)

if we know the suction pressure and temperature then why we find the FAD, Free air delivery shows what in compressor, is free air delivery use for suction or for delivery,

 Feb 19, 2014 FAD by: Doug in s.d.ca FAD is whatever is available to the intake of the compressor, and is the same whatever at the output.In other words, it's the real-world capacity at the moment. Or, CFM at the current environmental temperature and pressure.Not really terribly useful for comparing compressors, but tells you what you're getting, and opposed to SCFM.Does that help?

 Feb 18, 2014 FAD by: nawaz ya i read from wiki, but in some numericals suction pressure and tempratue given and FAD pressure prsurre temmp volume given, i mean why we considered FAD value,

 Feb 18, 2014 FAD by: Doug in s.d.ca Have you read the Wiki on it?It's part of "actual cubic feet per minute".It may have issues, but way better than nothing.

## Is 6 cfm low for my compressor?

by Leo
(Northern California)

I just picked up a used 33 gallon, 3HP, 2 cylinder 1979 craftsman.

Using the formula in the "Fill air tank" section, I come up about 6 cfm being delivered by this compressor.

That seems low to me considering its a 3 hp motor.

The numbers I used are: 100 psi kick in pressure, 132 psi kick out pressure, 33 gal tank, and 1 minute 25 seconds to go from 100 to132 psi.

Did I calculate correctly?

If 6 cfm is low, what could be wrong with this compressor?

By the way, it takes almost 6 minutes to fill the tank when it's completely empty.

Thanks for any pointers
_________________
Well, I'm not redoing calculations as my math is really suspect.

Rule of thumb is 3-4 CFM of flow at 90 PSI for each HP of motor.

However, if your compressor is running on 120 VAC, you aren't going to be able to get a true 3 HP performance.

For issues relating to compressors that don't build pressure properly, please see the pages linked from the troubleshooting section on the sitemap page.

Bill

### Comments for Is 6 cfm low for my compressor?

 Feb 08, 2014 Low cfm by: Leo Bill,Thanks for your reply. The compressor is 240v, and I was expecting more like 9 cfm out of this old girl. I'll check the troubleshooting section for tips on pressure build up problems. So a 240v, 3 hp motor should fill a 33 gallon tank faster than 6 minutes, you think?________________Yes, the recharge should be less than 6 minutes. But from a completely empty tank to a 140-150 PSI cut out, that doesn't seem inordinately long.B.