Air Tools & Airline pressure drop

[ventureoverland]

Bit of background first...

The other day I bought an Aldi Die Grinder. It was rubbish! The main problem was the inbuilt wobble feature of the collet - LOTS and LOTS of run-out. It was also very noisy. I could live with the noise, but not the wobble so I took it back. Then in a moment of weakness I started looking for a better unit and promptly bought an Ingersoll Rand 5108MAX. The difference is like chalk and cheese (not surprising really).


Anyway, this got me thinking about regulated pressure and the pressure drop along my airline so I could make sure I gave the 5108MAX the air it needs.

I knocked up this little thing tonight - simple inline gauge that plugs in just before the die grinder.

https://farm8.staticflickr.com/7775/17400787742_8b6a801a70_o.jpg (https://flic.kr/p/svDzXL)In-line Air Pressure gague (https://flic.kr/p/svDzXL) by Jon_Kelly (https://www.flickr.com/people/100552867@N05/), on Flickr

As a starting point I plugged it straight into the tank. As expected when the trigger is pulled the pressure remains the same. Its a different story 15m along the 10mm ID air hose - 20psi lost.

Just for fun I then plugged my 8m 6mm ID coiled hose into the end of the 15m hose and pulled the trigger again - 50psi lost:o:o:o

In summary:
- 0m hose, 0psi pressure drop
- 15m 10mm ID hose, 20psi pressure drop
- 15m 10mm ID hose + 8m 6mm ID hose, 50 psi pressure drop


My next question is what to set the regulator at? Should the gauge at the regulator read 90psi or adjust it until I get 90psi with an open trigger at the die grinder?

[Stustoys]

When I get worried about that sort of thing(is worried the right word? lol) I have a reg set up like your pressure gauge, which lets me run tank pressure in the line. For a die grinder I doubt you'd want the reg hanging off the end, so if you want to get excited, make up a belt clip* and a 1m line to go from the reg to the tool.
But then I dont think my compressor kicks in until 80psi anyway.

Stuart

*or other suitable nearby location.

[BobL]

Pressure drop is also strongly dependent on flow rates so to make a proper comparisons between the two lengths and hoses you need to attach a volume or mass flow meter

e.g. 20 PSI drop for a 15m 10 mm dam plastic hose suggests a flow rate of about 12CFM
The effect is strongly non-linear
e.g. If 6CFM is being used the Pdrop will only be ~6psi

Pressure drops are proportional to the fourth Power of the radius of the pipe being used so going from 10 mm to 12.5 mm diameter pipe makes a dramatic difference.
eg 12 CFM though a 15m x 12.5 mm pipe will lose PSI.

6mm hose is a complete dog for compressed air lines.
A 50 PSI drop in the second case suggests only a flow rate of 6 CFM is comimg out the end of that setup

BTW these can all be calculated using http://www.pressure-drop.com/Online-Calculator/index.html

[KBs PensNmore]

Without worrying where to set the regulator, as screwing it in/out all day would give me the pits, plus possibly wear out the regulator screw. I'd first work out how far from the compressor will my work area be, if it is 5 metres, check your pressure drop, if it is too much I'd use a bigger hose. At 10 metres, I'd run something like 1/2" hose or put in some pipe work with a receiver tank and run the regulator with a short hose from that.
I'm led to believe, that putting more pressure through the hose reduces quantity, due to friction losses.
I could be wrong, my partner, always say I am.
Kryn

[rogerbaker]

What I would be doing is running 3/4 Steel pipe around the workshop so that I only needed 3 or 4 metres of hose for the job.

Roger

[BobL]

What I would be doing is running 3/4 Steel pipe around the workshop so that I only needed 3 or 4 metres of hose for the job.

Roger

There's no need to use 3/4" pipe unless you need flow rates of 30+ CFM.
I have compressed air reticulated to all 4 walls of my shed so the longest run of 1/2" pipe in my shed is 8 m
If I use 12 cfm the pressure drop is a whopping 3 psi.

[ventureoverland]

Thanks for all the replies.

Bob, very interesting. I'll check out the link you gave.

Roger,
As funds allow I will be putting a 20mm or 25mm pipe around the garage and put the regulator on the end of that. I plan to have maybe a 5m or so 10mm ID hose to tools.

I use the 6mm coil hose for the blow gun only.

R
J


Thx
Jon

[rogerbaker]

"As funds allow I will be putting a 20mm or 25mm pipe around the garage and put the regulator on the end of that. I plan to have maybe a 5m or so 10mm ID hose to tools."

Hi Jon
When you do that make sure you put a Bleed valve on the bottom of any vertical runs. It is amazing how much condensation you can get especially if you are spray painting.

Roger

[BobL]

This might help.
This is for smooth plastic pipe 10m long with a pressure of 145psi in the tank - when the pressure in the tanks is lower the pressure drop will be less.
The different coulours are for different diameter pipe
Only one point is shown for 6 mm pipe because it cannot support flows of 10 CFM and above

http://www.woodworkforums.com/attachment.php?attachmentid=346499&stc=1

[Burner]

As funds allow I will be putting a 20mm or 25mm pipe around the garage and put the regulator on the end of that. I plan to have maybe a 5m or so 10mm ID hose to tools

I would encourage you to consider not putting steel pipe around the garage as the internal corrosion and hence rusty pieces ending up in the air stream system can be prevented by using copper or plastic air line. The galv pipe these days doesn't seem to be as good as the old stuff either.

[eskimo]

in the interests of ensuring/obtaining best flow rates BIGGER IS ALWAYS BETTER

[ventureoverland]

This might help.
This is for smooth plastic pipe 10m long with a pressure of 145psi in the tank.
The different coulours are for different diameter pipe
Only one point is shown for 6 mm pipe because it cannot support flows of 10 CFM and above

http://www.woodworkforums.com/attachment.php?attachmentid=346499&stc=1

Thanks Bob. This is one of those cases where a picture really does paint a thousand words! Just goes to demonstrate the benefits that can be gained by simply upsizing even a couple of mm in diameter.

R
J

[danielwaus]

Recently ran air line around my workshop, after searching the forum and finding this thread- http://www.woodworkforums.com/showthread.php?t=150421 ( thanks Phil ! ) I decided to use 20mm blue stripe irrigation line and philmac fittings.
Went to the local irrigation supplier and told him what I was thinking of using it for and he said most of the local tyre businesses use it for air.....
Main line slopes down gradually with drain at end- so far no moisture has collected but I do have a refrigerated dryer fitted just after the air compressor (bought second hand off ebay) Just plug in a small regulator to what ever outlet I'm using.
The last picture is of an inline digital air regulator, really handy, mostly use just before the spray gun....


Daniel



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[BobL]

I've been investigating installation of air lines for our Men's Shed.
One thing I have learned is that the tap off points from the trunk line should initially go upwards.
The other thing is to slope the trunk lines and put a tap on the end f the slope.
This will further minimise water transfer into hoses.

[Ben Dono]

Thumbs up for the blue stripe pipe and Philmac fittings. I just did the same thing in my workshop. I ran 50m of 25mm poly with lots of droppers around the workshop. It was pretty straight forward to do. Lots of compatible brass fittings that suit as well. I have a spray booth right at the end of the line and I still get a little mist in the pipes when I blow off the water trap. Every take off needs a water trap...well up here you do.

[ventureoverland]

Thumbs up for the blue stripe pipe and Philmac fittings. I just did the same thing in my workshop. I ran 50m of 25mm poly with lots of droppers around the workshop. It was pretty straight forward to do. Lots of compatible brass fittings that suit as well. I have a spray booth right at the end of the line and I still get a little mist in the pipes when I blow off the water trap. Every take off needs a water trap...well up here you do.

Ben,
What's the typical price for a 6m length of 25mm blue stripe pipe and associated fittings?

Just trying to gauge typical cost of this setup compared to say Aluminium air pipe and fittings. There's a place close to my work that does the "proper" ally air pipe, but I haven't costed it yet.

Thx
J


Thx
Jon

[texx]

local tyre bloke has 2 inch gal pipe running all over his workshop . the large pipe and a fair bit of it acts as a another storage tank .,

johno

[Ben Dono]

Jon I can't say I'm up to scratch on the prices but I did do a price comparison 3/4 copper vs gal pipe vs blue stripe 20mm and 25mm. Even though the joiners/bends/take off saddles are a lot more expensive in poly I still came out well in front. 25mm is not that much dearer for the pipe and fittings over 20mm so I just went with the larger.

Bunnies website is a good place to do a comparison on costs. A 50m roll of 25mm poly is about $50 and 6m of 19mm copper is about the same.
The pipe and Philmac fittings are rated to about 170psi working pressure. I'm only a running a standard 125psi setup so no problems there.

No leaks with hand tightening the fittings either. Very simple system actually. I just used electrial conduit half saddles (a box of them is cheap) to strap them to the walls etc.

Actually, one of the best things I did was a 7m long 19mm copper water Trap off the compressor before I joined into the poly. Pretty much all the water is trapped there before it gets into my lines.

One of the locals on this forum mentioned to plumb your compressor into your large water trap then back into the storage tank. Most of your water will end up in the copper trap before it makes it into your compressors tank. I will be doing this next time my compressor needs a bit of work. That was a good tip!

[BobL]

Ben,
What's the typical price for a 6m length of 25mm blue stripe pipe and associated fittings?

Just trying to gauge typical cost of this setup compared to say Aluminium air pipe and fittings. There's a place close to my work that does the "proper" ally air pipe, but I haven't costed it yet.
n

This post may be of value
http://www.woodworkforums.com/showthread.php?t=190528&highlight=reticulated

And here are some quotes for poly air pipe - this quote is about 6 months old.
The pipe is cheap - the fittings are not

http://www.woodworkforums.com/attachment.php?attachmentid=346633&stc=1