ovalandrover
Well-Known Member
- Posts
- 1,632
Ill just put my 2 pennath in dosent speed of pump as well as bore and stroke affect the cfm?
eas compressor cfm??
- Thread starter zen
- Start date
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- Posts
- 58,170
- Location
- Preston Lancs.
Yep it does. Motor will slow as it comes under pressure, air flow will reduce as pressure builds. It all as an effect.
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- 16,482
I get the feeling we are all arguing the same point, but from different directions....!!!
Pump Volume Flow Rates slow as pressure increases....
Pump Speed slows as pressure increases.....
In order to calculate fill time - the rise in pressure/time=decrease in Volume Flow rates so needs to be averaged over the entire fill process.....
Air Density and Composition hasn't been taken into account - Colder air will fill quicker....
Pump efficeny hasn't been taken into account....
Induced temperature during pressurising hasn't been taken into account.....
Tank Expansion hasn't been taken into account......
There are many variables to be considered.....
Can we all agree that a good pump should fill the tank in the region of 6-10 minutes on a good day regardless of whatever the flow rates are??
Pump Volume Flow Rates slow as pressure increases....
Pump Speed slows as pressure increases.....
In order to calculate fill time - the rise in pressure/time=decrease in Volume Flow rates so needs to be averaged over the entire fill process.....
Air Density and Composition hasn't been taken into account - Colder air will fill quicker....
Pump efficeny hasn't been taken into account....
Induced temperature during pressurising hasn't been taken into account.....
Tank Expansion hasn't been taken into account......
There are many variables to be considered.....
Can we all agree that a good pump should fill the tank in the region of 6-10 minutes on a good day regardless of whatever the flow rates are??
- Posts
- 58,170
- Location
- Preston Lancs.
Not arguing with anyone, apart from the person who thinks a pump of 1 cu ft a minute free air capacity, will inflate a 1 cu ft tank to 140 psi in 1 minute, it just cannot happen. As we well know.
- Posts
- 58,170
- Location
- Preston Lancs.
I think we should start by agreeing that a 1cfm pump will shift 1 cu of air (at atmospheric pressure) in one minute and then move on up from there, lol
Hey no problem. But what you have to think of is this. A standard atmosphere is 14.7 psi. So to raise that to 140 psi it has to be compressed into an area around 9.53 times smaller than the space it took up as free air. So the output of the cylinder is 9.53 times less at 140 psi that it would be at 14.7 psi pumping free air.
