Compressor Hose Size

[Jerry Chabino]

Guys,

I have a question. My compressor has a 6 ft 3/8 hose on it now.
I want to increase the hose to either 25 or 50 ft. Should I jump up to a 1/2" hose? My new impact wrench directions say to go to 1/2" with the last part near the wrench cut down to 3/8"
Thanks in advance for the help and HAPPY HOLIDAYS.

Jerry

[Dan Semko]

Jerry,
Not a problem because the psi's remain the same regardless of hose diameter. If the tools feel sluggish, just up the compressor psi output. Think of it similar to tire inflation settings. If you put 35 psi in a 15" tire and similarly put 35 psi in a 26" Kubota tractor tire, then measure it with a gauge, the volume will be different, but the pressure per square inch remains constant.

[conway]

Check the CFM ( cubic feet per minute) requirement for the tool and also the CFM output of the compressor . Also pressure drop on a 5/16 " hose @ 90 psi , 7.5@10' 9.5@20' . It takes a lot of CFM's to run an air wrench and of course you need the correct pressure.You may have to wait for the compressor to "catch up "between tasks. A large tank of reserve air will help.

Merry Christmas,
Conway

[Jerry Cowing]

Jerry,

What Dan said above is true. However, the volume of air available to run air tools is also very important. The hose diameter is one factor in the volume of air available to run your tools, another is the storage tank size (60-80 gal prefered) and another is whether it's a single or two stage pump with the two stage pump producing the most sustainable volume of air.

The larger the diameter of your hose (storage tank, pump, etc. remaining constant) the more volume of air you will have to operate your tools and the better they will maintain the proper pressure/volume specified by the manufactuer for the particular air tool you are using.

Bottomline: a bigger hose diameter is better -- to a practical limit of course.

[trularin]

You can do a 2 step.

Run a 1/2" ( or bigger ) out, say 25 to 50 feet. Then, switch to a 3/8 if you like.

I run 3/4" to a 1/2". Uses a lot of air when you are sand blasting, but the results are consistent.

For your average shop, get the 1/2 and not worry about it.

Heck, I think Harbor Freight has them on sale.

Just an additional $0.02

[Jerry Chabino]

Thanks for the info guys. I think I'll run the 1/2" the whole 25 ft. and add a water filter.
Happy New year

[Tom Kirkham]

A point of clarification...

What Dan said is true, but only in the static case.

In the dynamic case (i.e. when their is flow, such as when you are operating your impact gun) the diameter of the hose makes a huge differance.

Let us do a little experment. Try blowing through a tiny straw, now blow through a 2 inch exhaust pipe. As you can see the harder you blow on a tiny straw the more restriction you feel when you blow. On the other hand when you blow through a 2" exhaust pipe your lungs do not have enough capacity to generate enough restriction for you to feel.

For those who want a little bit more information The Compressed Air and Gas Handbook, Fifth Edition, ISBN 0-13-162611-6, page 824 we find the formula for air pressure drop.

The formula is:
pressure drop = (.1025 * Length of pipe in ft * cubic feet of free air per secound ^2 / (ratio of compression at entrance of pipe* actul internal diameter of pipe in inches^5.31)

^ means to the power of, so 2^3=8

Hope this helps

[David Kirkham]

I guess Thomas, with the help of The Compressed Air and Gas Handbook, just proved size does matter...

David

[rdorman]

Originally posted by David Kirkham


I guess Thomas, with the help of The Compressed Air and Gas Handbook, just proved size does matter...

David

There has got to be a fart joke in here some where. Where is Jamo any ways?
Rick

[Double Venom]

Jery,
We built all our lines with 1" black pipe, nipple off for the dryer then run the dryer off of that. The new shop will most likely be 1" schd. 90 plastic! Cheap, don't need to be a plumber and easy to make any "drops" that you might need.

If you really want to be cool, at the end put in (make) a long sideways "T". The air will come in from the top of the little leg, remember I said sideways, the dryer will come off the long leg, and the bottom you can put on a "faucet" if you will. Then when you think your lines have water in them, just open the faucet to drain!

DV...wish I kew how to use Windows drawing program better!

[Dan Semko]

Thomas,
Your formula is indeed correct provided that the fitting is not reduced at the impact wrench. When the fitting diameter is smaller than the production source, the pressure is increased. The demand remains constant but the initial volume changes inversely to the pressure and the length which from 3/8 to 1/2 then back to 3/8ths would be marginal. Using your example, if we take a swizzle straw and a regular straw of equal lengths with the same exit opening (port) and measure the restrictive pressure, it will remain constant in both straws exit end.

[Tom Kirkham]

Not if the straw is long enough.

BTW it would be pretty silly to have a 1/2 in hose and neck it down to 3/8 at the tank.

[David Kirkham]

Dan,

Now you have Thomas talking about size AND length...

David

[ERA649]

But, most air tools have 1/4" npt threads on the inlet so use 3/8 ID hose with 1/4" npt ends. This is the most popular hose combo.
I have used my 1/2 IR impact wrench for years and have had no problems with 50 ' of hose, a 150' is a different story. As for sand blasting it's not fun at all, just don't do it.

[Dan Semko]

Thomas,
I agree but this is what Jerry stated:
" want to increase the hose to either 25 or 50 ft. Should I jump up to a 1/2" hose? My new impact wrench directions say to go to 1/2" with the last part near the wrench cut down to 3/8"

Gotcha!

[Tom Wells]

Hey DV!

Be careful about plastic pipe & compressed air

Look at this URL:

No PVC pipe! ABS is OK!

PVC, when it fails, it splinters. Ouch

Take care,

Tom

[Tom Kirkham]

Not if you pull out the reducer bushing in the tank

[Double Venom]

Tom,
I thought schedule 90 WAS ABS. Not an expert in this field at all, but will certainly do some more research before we put it in the new shop!

Thanks for the heads-up!

Anyone have more info on this?
DV