CFM question

[Rainman7]

How many CFM can go through a .5" pipe @ 100psi?

Thanks

[Wet_Boots]

CF of what? That makes a difference. Water? Air? Maple Syrup?

[bicmudpuppy]

Just for fun, lets use AIR. IS there a formula out there? using a coefficient for the fluidity of the gas or liquid being "pushed", how much can you move through a pipe or hose of x size?

[Kiril]

Just for fun, lets use AIR. IS there a formula out there? using a coefficient for the fluidity of the gas or liquid being "pushed", how much can you move through a pipe or hose of x size?

Boots would just look it up in a flow chart and convert GPM to CFM. :laugh:

[Waterit]

IS there a formula out there?

Paging Dr.'s Kiril and Wet Boots.

[Wet_Boots]

For lengths of pipe, there are friction loss tables. For a short bottleneck like a hose bib, you'd have to do some guesswork. I had a sprinkler system that got fed from a 1/2-inch nipple that replaced a boiler drain, next to the 1-1/2 inch water meter, and after the one-inch copper reached the outdoors from the interior basement boiler room, I did some flow-and-pressure tests to see just how much water I had to work with. Quite a bit, actually.

[Kiril]

Paging Dr.'s Kiril and Wet Boots.

I expect you would want some derivative of the Euler Equations.

[Waterit]

I expect you would want some derivative of the Euler Equations.

Which are...

::::sorry, had to to do it::::

[Mike Leary]

It just never ends. :wall

[Wet_Boots]

Of course. the question should be "I have a *** CFM compressor, and want to push air through ***, so will it work?"

Another lame question.

[Tom Tom]

How many CFM can go through a .5" pipe @ 100psi?

Thanks


Not an exact answer , but,

The 1/2" pressure regulator on my compressor is rated at a max flow of 212 cfm at 70 psi.

[Wet_Boots]

All of which goes to show that air is less viscous than water. I would've given a nod to 100 cfm, based solely on guesswork.

[Kiril]

Which are...

::::sorry, had to to do it::::

http://www.ams.org/bull/2007-44-04/S0273-0979-07-01181-0/S0273-0979-07-01181-0.pdf

[Wet_Boots]

Uh-oh...... ;)

[bicmudpuppy]

Now I know how bad I do NOT want to know the answer :( 22 pages of physics w/o tables. Without the proper references, it would probably take half a day to get the variables right enough to get wrong answer.

[Kiril]

All of which goes to show that air is less viscous than water. I would've given a nod to 100 cfm, based solely on guesswork.

Is this I, S, or A CFM or FAD?

What is the delivery pressure at the point of use and at what pipe length and material?

What type of compressor you using (rotary screw, rotary centrifugal, reciprocating) or are you just using a blower?

What temperature and altitude?

For example:

An 1/2" orifice with an upstream pressure of 100 Psig will discharge 411 CFM of free air. (ref (http://www.sullairhouston.com/pdf/Air%20Metrix%20Card.pdf))

A 6" pipe/duct will average 110 CFM at 0.1 static pressure (ref (http://www.gaf.com/Content/GAF/METALDUCT/LLBP_Duct_Installation.html?WS=GAF&Silo=METALDUCT&App=DUCTINSTTIP&Uid=#ductsize2))

In short ... don't guess.

[Kiril]

Now I know how bad I do NOT want to know the answer :( 22 pages of physics w/o tables. Without the proper references, it would probably take half a day to get the variables right enough to get wrong answer.

No references? I counted over 40.

[Tom Tom]

Is this I, S, or A CFM or FAD?

What is the delivery pressure at the point of use and at what pipe length and material?

What type of compressor you using (rotary screw, rotary centrifugal, reciprocating) or are you just using a blower?

What temperature and altitude?

For example:

An 1/2" orifice with an upstream pressure of 100 Psig will discharge 411 CFM of free air. (ref (http://www.sullairhouston.com/pdf/Air%20Metrix%20Card.pdf))

A 6" pipe/duct will average 110 CFM at 0.1 static pressure (ref (http://www.gaf.com/Content/GAF/METALDUCT/LLBP_Duct_Installation.html?WS=GAF&Silo=METALDUCT&App=DUCTINSTTIP&Uid=#ductsize2))

In short ... don't guess.

Whens the next earthquake in CA?

[Wet_Boots]

................... In short ... don't guess.The OP gave no choice but to make guesses, based on the info supplied. When I did my screwball system tie-in at a former boiler-drain location, I ran tests, rather than look up anything. Of course, knowing that the ID of a 1/2-inch nipple is close to the ID of a 3/4-inch ball valve (of the 'conventional' dimensions) made the method of supply a reliable one.

[Kiril]

Whens the next earthquake in CA?

Not nearly soon enough. :laugh:

[WalkGood]

. Of course, knowing that the ID of a 1/2-inch nipple is close to the ID of a 3/4-inch ball valve (of the 'conventional' dimensions) made the method of supply a reliable one.

Ummm, isn't a full port ball valve just that....? The full amount of the inside diameter of the size in question?

The ID of a 1/2 inch nipple is a lot smaller than the ID of a 3/4 inch ball valve.

[Wet_Boots]

Ummm, isn't a full port ball valve just that....? The full amount of the inside diameter of the size in question?

The ID of a 1/2 inch nipple is a lot smaller than the ID of a 3/4 inch ball valve.Tsk. And tsk. You didn't know there were three different specs for ball valves? Full port is one of them. There is also "conventional" and "standard" ~ a 3/4-inch 'standard' ball valve has a 1/2-inch opening. A 'conventional' is a bit larger.

[WalkGood]

Tsk. And tsk. You didn't know there were three different specs for ball valves? Full port is one of them. There is also "conventional" and "standard" ~ a 3/4-inch 'standard' ball valve has a 1/2-inch opening. A 'conventional' is a bit larger.


Tsk tsk is right. I figured you would *only* use full port valves. :) But I imagine you will report that the ball valve was pre-existing?

In my world (in my mind that is), only full port ball valves exist. Everything else is dinky cheapo! LOL

[Wet_Boots]

It's an easy 'gotcha' Mister Palin :) Improved manufacturing makes full-port more common than ever. I only used a few of the 'standard' port valves, of a side-entry type that would cost a fortune today.

[Mike Leary]

Everything else is dinky cheapo! LOL

Excuse me, I think you meant to say, "piker dinky cheapo."

[Waterit]

Excuse me, I think you meant to say, "piker dinky cheapo."

Excuse me, I think you meant to say, "dorky piker dinky cheapo."

[WalkGood]

It's an easy 'gotcha' Mister Palin :) Improved manufacturing makes full-port more common than ever. I only used a few of the 'standard' port valves, of a side-entry type that would cost a fortune today.

Got any pics for comparison?

BTW, what prevented you from changing over to a full port valve? Was the supply piping 1/2" ?

[Wet_Boots]

Got any pics for comparison?

BTW, what prevented you from changing over to a full port valve? Was the supply piping 1/2" ?No, the water meter and supply line was 1-1/2 inch, and the lawn was less than half an acre. But the meter was in an interior utility room of a fully finished basement of an office building, and almost impossible to work on. Too crowded. But there was that boiler drain, threaded into a fitting, and conveniently pointing upwards. So, mulling it over, one could envision an old-style 3/4-inch ball valve in place of the nipple I was going to thread in, and that would mean at least 10 gpm without much loss.

[zimmatic]

If it is Air cfm this table may help http://www.engineersedge.com/pipe_flow_capacity.htm
and http://www.engineeringtoolbox.com/scfm-acfm-icfm-d_1012.html

[Kiril]

Here is a collection of articles on compressed air.
Some people might want to take a close look at the article The secret is in the pipe

http://www.putman.net/brands/ps/downloads/ps_compressed_air_articles.pdf

[turfman59]

air is traveling into the pipe but at the point it cannot come out fast enough is starts to compress inside of the pipe and act like a resevoir....to me you asked a pretty generic question to answer

[Mike Leary]

like a resevoir....

Bring back spellcheck! :hammerhead:

[turfman59]

Bring back spellcheck! :hammerhead:

you knew what I meant...anything to raise the amount of posts I guess...Did you have anything to add constructive or did you just want to bang your high chair today....

[Mike Leary]

.Did you have anything to add constructive or did you just want to bang your high chair today....

It was not directed at you, geez, some pretty thin skins around here; is it the end of the season PMS for sprinkler guys?

[Wet_Boots]

I vote highchair :rolleyes:

[Mike Leary]

I vote highchair :rolleyes:

Works for me.

[Wet_Boots]

Where's your sippy-cup of Arizona merlot?

[Mike Leary]

Where's your sippy-cup of Arizona merlot?

Oops, wrong pic.

[turfman59]

It was not directed at you, geez, some pretty thin skins around here; is it the end of the season PMS for sprinkler guys?
No not at the end of the year I finally have positive Balance in my Checking account...And I happen to keep myself busy all winter long watching Opra

[Rainman7]

Sorry for the delay, I've been pretty busy. I see there has been some action here.

To clarify.. yes CFM=Air....I guess it could have been water but in the irrigation world I consider water gpm and fps.

The reason for the question is I tried a hose reel with .5" fem. ports and put my 1" air hose on it. When winterizing a familiar system, I noticed that the compressor(185cfm@100psi) was not laboring the way it should and the system was not blowing out properly. I then connected the hose directly to another port on the compressor and volia(spell check) worked perfect.

Thats the reason for the question. I since then returned the hose reel and ordered a .75".

I am still curious on how much air can go through 18" of .5" pipe @ 100psi.

[turfman59]

Sorry for the delay, I've been pretty busy. I see there has been some action here.

To clarify.. yes CFM=Air....I guess it could have been water but in the irrigation world I consider water gpm and fps.

The reason for the question is I tried a hose reel with .5" fem. ports and put my 1" air hose on it. When winterizing a familiar system, I noticed that the compressor(185cfm@100psi) was not laboring the way it should and the system was not blowing out properly. I then connected the hose directly to another port on the compressor and volia(spell check) worked perfect.

Thats the reason for the question. I since then returned the hose reel and ordered a .75".

I am still curious on how much air can go through 18" of .5" pipe @ 100psi.
a lot of air,,, I blow out the majority of my residentials with a 1/2 inch hose..It starts to show up when the system is designed at 18 gpm fer minute and up

[turfman59]

when the system is nozzled at 18gpm and up the heads have hard time staying up after the water is out of all of them....12 gpm systems my 1/2 inch hose at 125 feet is adequate...hope this helps

[Mike Leary]

Someone shoot me.

[turfman59]

Someone shoot me.
357 or would you like it to hurt a little more....??? how about a 22 caliber in the groin :usflag:

[hoskm01]

Ill offer .40 cal with hollow points or 12 ga. buck or bird, your choice.

[turfman59]

Ill offer .40 cal with hollow points or 12 ga. buck or bird, your choice.
isnt fort collins where they make the Walker Mower

[Mike Leary]

Ill offer .40 cal with hollow points or 12 ga. buck or bird, your choice.

I'll take the quick way; I trust hoskm01.

[hoskm01]

isnt fort collins where they make the Walker Mower
Along with New Belgium and Anheuser Busch beers, yes.


Walkers are everywhere up here, though the turf at their place isnt anything to get up from dinner over.

[bicmudpuppy]

Sorry for the delay, I've been pretty busy. I see there has been some action here.

To clarify.. yes CFM=Air....I guess it could have been water but in the irrigation world I consider water gpm and fps.

The reason for the question is I tried a hose reel with .5" fem. ports and put my 1" air hose on it. When winterizing a familiar system, I noticed that the compressor(185cfm@100psi) was not laboring the way it should and the system was not blowing out properly. I then connected the hose directly to another port on the compressor and volia(spell check) worked perfect.

Thats the reason for the question. I since then returned the hose reel and ordered a .75".

I am still curious on how much air can go through 18" of .5" pipe @ 100psi.

I would bet your restriction isn't the 18" of half inch pipe, but the fittings involved.

Is there a REASONALBE (I almost said "good") rule of thumb to convert CFM of air to GPM? Or, if you have a system that normally runs x gpm @ 80psi, what CFM of air equates? (we can even assume identical operating pressure)

What I *think* I am looking for is a viscosity comparison of "air" vs water. Working from the gut, I expect the answer (if there is one) to be around 5?
i.e. a 10gpm system needs around 38cfm to "work" Or, that 100cfm compressor stops running zones fully when the system exceeds 30gpm? I know a 185 will blow most 2" systems. I've blown systems that run very close to 90gpm with a 185, but the larger zones (actually approaching the 90gpm) bogged down and letting the compressor "catch up" before blowing them again was a good idea.

[Wet_Boots]

I would think a 10 gpm zone could be blown out with any dinky on a 20-gallon tank, if pressure was built up before the zone was opened.

[WalkGood]

gpm and cfm are all units of volume.

Gallons per minute. Cubic feet per minute.

Convert gpm to cfm : multiply gpm by 0.1337 to get cfm.

Convert cfm to gpm : multiply cfm by 7.481 to get gpm.

[Rainman7]

Sorry, still no help...but thanks for the lesson.

In my small world of irrigation I talk CFM in the winter and GPM/FPS in the summer. Have not found the need to convert yet.

I am guessing that there is no easy answer to this question or it is dependant on many factors. It took maybe 2 minutes to resolve the problem with a larger connection but I was just curious if there was a general rule of thumb.

Thanks again.

[Kiril]

Sorry, still no help...but thanks for the lesson.

In my small world of irrigation I talk CFM in the winter and GPM/FPS in the summer. Have not found the need to convert yet.

I am guessing that there is no easy answer to this question or it is dependant on many factors. It took maybe 2 minutes to resolve the problem with a larger connection but I was just curious if there was a general rule of thumb.

Thanks again.

Tsk, tsk, you didn't look at my links. :nono:

[bicmudpuppy]

gpm and cfm are all units of volume.

Gallons per minute. Cubic feet per minute.

Convert gpm to cfm : multiply gpm by 0.1337 to get cfm.

Convert cfm to gpm : multiply cfm by 7.481 to get gpm.

But, your missing the main point of the difference between the viscosity of air vs water. The piping will move more air vs water because the air is more fluid than the water.

[Rainman7]

Is this I, S, or A CFM or FAD?

What is the delivery pressure at the point of use and at what pipe length and material?

What type of compressor you using (rotary screw, rotary centrifugal, reciprocating) or are you just using a blower?

What temperature and altitude?

For example:

An 1/2" orifice with an upstream pressure of 100 Psig will discharge 411 CFM of free air. (ref (http://www.sullairhouston.com/pdf/Air%20Metrix%20Card.pdf))

A 6" pipe/duct will average 110 CFM at 0.1 static pressure (ref (http://www.gaf.com/Content/GAF/METALDUCT/LLBP_Duct_Installation.html?WS=GAF&Silo=METALDUCT&App=DUCTINSTTIP&Uid=#ductsize2))

In short ... don't guess.


Is it pipe or an orifice? A .5" orifice will leak 411 CFM @100psi but according to the chart below that, the max recommended cfm through a 3/4" pipe is 22 @ 100psi.

Something don't seem right for our application. Think i'm going to get one of those plug in Sears compressors...that should do the trick.

[bicmudpuppy]

The numbers in the second chart for piping size are a lot like our numbers for piping size with water. If you reverse the trend to get a 60psi rating for 1" pipe, your going to be around 38 or 37 cfm. This would be for CONTINUOUS working operation. If you read some of the other links he has provided, you want to stay under those ratings so the air DOESN'T pick up water. We are blowing the curve because we WANT to pickup water. If we don't, we aren't achieving our application! So, the guy with the dinky compressor who *thinks* he is getting it done, obviously isn't, because to move MORE than 40 CFM through his 1" irrigation lines so that he picks up the water can't happen with a 10cfm compressor unless he is charging and re-charging over and over and over and over and over etc. I wish the numbers in the chart had continued. I'm real curious how much air an 8" line can handle within their operating curves. Getting to +25% of that might be a challenge :) Glad my large mains are below frost depth and the largest lines I actual have to get dry are 2.5" :cool2:

Compressor should be here this AM!! I'm hoping within the hour. I'm going to call when they open in a few minutes. I was hoping they would drop the machine last night and it would have been here when I got to work almost an hour ago.

[Kiril]

The other link.

http://www.lawnsite.com/showpost.php?p=2577393&postcount=29

Is it pipe or an orifice? A .5" orifice will leak 411 CFM @100psi but according to the chart below that, the max recommended cfm through a 3/4" pipe is 22 @ 100psi.

The orifice number shows you how much air will pass through a hole of x size to the open atmosphere at an upstream pressure of y.

The pipe number shows you how much air you can push through 100' of pipe of x size with only a 0.5 psi drop (i.e. your pressure at 100' with a starting pressure of 100 PSI in 3/4" pipe will be 99.5 psi). I imagine you can use both charts to roughly determine how much air you can push through x length of y size pipe in order to get the pressure you need to pop the sprinklers.

A good exercise would be to use the formula given in the other link I posted, and compare it to a number you get using the charts to see if in fact you can use the charts in this manner.

... or you can work through the Euler equations to get an exact number.

[Tom Tom]

TIf you reverse the trend to get a 60psi rating for 1" pipe, your going to be around 38 or 37 cfm. This would be for CONTINUOUS working operation. If you read some of the other links he has provided, you want to stay under those ratings so the air DOESN'T pick up water. We are blowing the curve because we WANT to pickup water. If we don't, we aren't achieving our application! So, the guy with the dinky compressor who *thinks* he is getting it done, obviously isn't, because to move MORE than 40 CFM through his 1" irrigation lines so that he picks up the water can't happen with a 10cfm compressor unless he is charging and re-charging over and over and over and over and over etc. I wish the numbers in the chart had continued. I'm real curious how much air an 8" line can handle within their operating curves. .

8" pipe is 64 times larger than 1" pipe. So using your 40 cfm for 1" = 2560 cfm for 8"

[AI Inc]

all this math and Boots isnt here yet, he's slipping.

[WalkGood]

With very large mains, like 6" or 8", is it very likely that 1/3 to 1/2 the "depth" of the horrizontal runs still have water in them after a blowout attempt? Meaning, the air finally gets out of the pipe and finds it easier to just "slip on by" over the remaining water and not push out any more water.

[Waterit]

Between this thread and the "how-to-modify-Firefox" thread I fear my brain will explode before I can decide who to vote against today...

[Kiril]

The numbers in the second chart for piping size are a lot like our numbers for piping size with water. If you reverse the trend to get a 60psi rating for 1" pipe, your going to be around 38 or 37 cfm. This would be for CONTINUOUS working operation. If you read some of the other links he has provided, you want to stay under those ratings so the air DOESN'T pick up water. We are blowing the curve because we WANT to pickup water. If we don't, we aren't achieving our application!

Exactly. The velocity of the air will determine if you are going to successfully blow out your system or not.

@Rainman7

Here is a calculator that comes with a theory breakdown. The more variables you have to feed the calculator, the more accurate your result will be.

http://www.pipeflowcalculations.com/airflow/theory.htm

[Wet_Boots]

Better vote soon, and release some of that stagnant pressure. http://img389.imageshack.us/img389/3115/smileysafterchilici7.gif