Distance from compressor to tanks - does it make a difference in speed of fill?

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Divemaster No.1

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It's in the title really; i've been told our compressor is filling more slowly than expected because the tanks are too far away from it, something i've never heard before.

Does anyone have experience in this please? Is it really the case?

Thanks guys, i'm very new to compressor stuff so any help appreciated
 

lermontov

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cant see how this is the case -once a line is filled with the correct pressure then its the same but obviously itll take a fraction longer to reach that pressure in a long line- if you're doing short fills then releasing all the pressure in that line and then reconnecting and rebuilding pressure then yes it will be slower.
 

Tracy

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Yes, but in reality, no. How far are we talking? Some of my banks are 200' away, outside of the time to fill the line connecting the two, there shouldn't be any difference.
 

Tracy

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They're no more than 20 feet away.

Thanks for the help by the way guys!
That isn't your issue. Your slow fill is probably a leak somewhere.
 

Angelo Farina

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They APPEAR to fill more slowly, as during the travel along the long pipe the temperature diminishes, so your tank is getting a "cold fill" instead of an "hot fill". The indicated pressure is lower, but the amount of air pumped in (in kg) is the same...
Which actually is a good thing.
With an "hot fill", after one hour your pressure will drop 10% or more. With a cold fill, your pressure remains almost the same also hours after the filling is complete.
 

BoltSnap

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They're no more than 20 feet away.

Thanks for the help by the way guys!

I have had my fill station more than 50 feet away from the compressor without any issues at all.
 

tbone1004

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I use a 100ft fill whip most of the time that I fill.

Now, technically it does decrease the fill rate because you are now filling the entire volume of the hose which is not actually inconsequential.
That 100ftx1/4" hose has an internal volume of .034cf~1L which means that the compressor has an extra 8-10cf of gas to pump to fill the hose from empty to 3600psi.
If you assume the hose is empty when you start, for most compressors that will be about 2 minutes of extra filling required to fill it back up on the first tank. Since I have a shutoff valve at the end of the hose, it doesn't take any longer on subsequent fills.
There is also friction in that pipe to consider as well as pressure drop during flow, but the gas is moving slow enough that this is going to affect it by maybe a second or two, hardly anything to discuss.
 

Rol diy

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I originally thought you meant line loss.
Like it has to small a hose and you are using to much flow... but for filling dive tanks it would need to be very small hose.
Now a high volume air compressor into your banks... its possible...
it would create more heat. And pressures would be higher at the compressor
 
https://www.shearwater.com/products/swift/

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