Air Compressor Math Problem

[bigtiller]

My air compressor makes 15.2 acfm at 175 psig. But it isn't stated how much cfm's it can make at 90 psi. I'm guessing it can deliver more cfm at lower pressures.

Anyone good at math?

 

[IH3444]

https://www.northerntool.com/shop/tools/product_200350475_200350475

 

[zzvyb6]

My air compressor makes 15.2 acfm at 175 psig. But it isn't stated how much cfm's it can make at 90 psi. I'm guessing it can deliver more cfm at lower pressures.

Anyone good at math?

P1*V1 = P2 * V2

so 175*15.2 / 90 = ~29.5 cfm

 

[bigtiller]

https://www.northerntool.com/shop/tools/product_200350475_200350475

The specs. are 15.4 cfm at 90 psi. I'm fairly sure that is a misprint. That is why the question.

 

[LouNY]

When I follow your link and look at the specs. I see;
CFM at 90 PSI 15.4 CFM
at Max. PSI 15.2 CFM
It is a two stage compressor so its not losing a lot with the pressure increase.

 

[RedNeckRacin]

P1*V1 = P2 * V2

so 175*15.2 / 90 = ~29.5 cfm

That is a static environment equation and not anywhere close to describing a compressors output. Just like P1T1=P2T2. Pumps always have a pump curve. More pressure = less flow and vice versa.

 

[ddbackhoe]

My air compressor makes 15.2 acfm at 175 psig. But it isn't stated how much cfm's it can make at 90 psi. I'm guessing it can deliver more cfm at lower pressures.

Anyone good at math?

What compressor do you have? You have acfm (actual cubic feet/minute) listed. Normally, compressors are rated for SCFM (standard cubic feet/minute). Barometric pressure, temp and relative humidity have to be factored in for the conversion from ACFM to SCFM.

 

[bigtiller]

What compressor do you have? You have acfm (actual cubic feet/minute) listed. Normally, compressors are rated for SCFM (standard cubic feet/minute). Barometric pressure, temp and relative humidity have to be factored in for the conversion from ACFM to SCFM.

https://www.northerntool.com/shop/tools/product_200350475_200350475

I have the one referenced by IH344.

I could call the manufacturer but I'm pretty sure the girl that answered the phone would just read the published specs. back to me.

Will lower pressures produce a higher cfm?

 

[PILOON]

Will lower pressures produce a higher cfm?

From all compressor specs that I have seen that rate at different pressures, YES.
But don't ask me how much.

 

[ddbackhoe]

I have the one referenced by IH344.

I could call the manufacturer but I'm pretty sure the girl that answered the phone would just read the published specs. back to me.

Will lower pressures produce a higher cfm?

In reality, not by much. CFM is cfm, the compressor pump displacement is rated for x cfm. that's why I was asking about acfm. Standard cubic feet per minute determines the weight of compressed air at 14.696 pounds per square inch, 60 degrees Fahrenheit and zero percent relative humidity, at sea level. Corrections should be made based on where the equipment was manufactured, although I 'd bet some of them cheat and just use the compressor head specs. regardless of rpm input.
Acfm calculations try to account for pressure, humidity and temperature as the gas (air) expands and contracts. As temps fall it contracts and expands as they rise.

Anyway, these are both measures of flow derived from inlet conditions. So, you have the displacement, now the flow will be determined by your local conditions for inlet density. Will your air tools notice the difference, well that depends.....

This may help SCFM versus ACFM and ICFM

 

[doneill127]

There’s two stage 175 psig Northstar at Northern tool that’s rated at 15.5@ 90 and 17 @ 40.

 

[bigtiller]

In reality, not by much. CFM is cfm, the compressor pump displacement is rated for x cfm. that's why I was asking about acfm. Standard cubic feet per minute determines the weight of compressed air at 14.696 pounds per square inch, 60 degrees Fahrenheit and zero percent relative humidity, at sea level. Corrections should be made based on where the equipment was manufactured, although I 'd bet some of them cheat and just use the compressor head specs. regardless of rpm input.
Acfm calculations try to account for pressure, humidity and temperature as the gas (air) expands and contracts. As temps fall it contracts and expands as they rise.

Anyway, these are both measures of flow derived from inlet conditions. So, you have the displacement, now the flow will be determined by your local conditions for inlet density. Will your air tools notice the difference, well that depends.....

Thanks, that helped

From the factory reviews....as I figured, not much help.

Question
What is the SCFM at 90 PSI? I understand the CFM; however, the SCFM is not listed and hopefully will be at or above 12.6

Answer
The SCFM is dependent upon several variables, such as, air temperature, humidity level and sea level.

 

[IH3444]

How about finding out what manufacturer for you pump, it's model number, the rpm, and go from their. The manufacture should know the numbers.

 

[ddbackhoe]

Thanks, that helped

From the factory reviews....as I figured, not much help.

Question
What is the SCFM at 90 PSI? I understand the CFM; however, the SCFM is not listed and hopefully will be at or above 12.6

Answer
The SCFM is dependent upon several variables, such as, air temperature, humidity level and sea level.

based on their acfm data, scfm would be 11.8. What kind of tools are you using? Aren't they listed as something like 4 cfm @90 psi?

http://www.industrialairpower.com/wp-content/uploads/Air-Compressor-Consumption-Charts.pdf

 

[bigtiller]

based on their acfm data, scfm would be 11.8. What kind of tools are you using? Aren't they listed as something like 4 cfm @90 psi?

My largest cfm use tool would be the blowgun, or as I sometimes jokingly refer to as a pneumatic broom. So, no special need for high cfm's, just curious is all.

 

[Dave M7040]

Your issue is a 175 psi compressor is a two stage one in order to achieve 175 psi.

With normal home shop compressors, you get two flow rates but because these compressors don't reach anywhere near 175, psi you don't suffer the inefficiency of a two stage and the pressure volume relationship is much more linear.

Compare the size of the 175 psi compressor cylinders. One large one feeding a small one. Lowering the pressure does not remove the fact that the compressor has a small and large cylinder and thus suffers from the lower efficiency of a two stage.

Delivered CFM 22.1 CFM @ 100 PSI / 16.2 CFM @ 175 PSI

Single stage compressors good for about 135 psi may have two same size cylinders to increase the volume output

Dave M7040