Air Hose: 3/8" vs 1/2"

[4wd]

In sensitivity to pressure loss - ID and length combine for greater impact... With a large enough ID and short enough length - there will be enough energy at the final fitting to provide good flow. However - the OEM of the end device can provide this info.

 

[SubLGT]

Originally Posted By: bmwpowere36m3
Fittings are just a restriction and flow is NOT "limited" by them... in the sense, 1/4" air line with 1/4" fittings = 3/8" line with 1/4" fitting, is false in common air setups...


The popular Milton 1/4" M-style coupler and plug are rated by MIlton at 40 SCFM, which sounds more than adequate for any 3/4" drive impact wrench.

But nowhere on the Milton website is it explained what the "standard" conditions are when SCFM is tested. Is it 90psi? 300psi? Is it at 60degF? 100degF? Other?

 

[bmwpowere36m3]

Per MIL standard, I/M-fittings require min: 35 CFM @ 100psi, 70*F and 2.5 psi max drop.

 

[Linctex]

At work, for REALLY high flow needs, we gang small hoses together in a manifold with one large hose outlet.

 

[4wd]

Yep - also ... pigtails can be rigged for safety (isolation of large hose inventory/potential energy) and ease of handling tools

 

[brages]

Originally Posted By: SubLGT
The HF 3/4" impact wrench (Central Pneumatic) I bought today is 7cfm at 90psi.


As was mentioned previously in this thread, that is an average air flow assuming a 25% (20?) duty cycle. So the wrench actually needs 4-5X that amount.

 

[JHZR2]

OP, there are a few items to consider...

Each component in the system has a pressure drop associated with it.

So you must consider the first fitting, (then really the hose crimp onto the hose thread), then the hose length, then the end fitting.

The first and end fittings are orifices, smaller than the pipe ID, so they will restrict flow.

The pipe will have some pressure drop in psi/ft. Bigger ID will have less drop.

 

[Rand]

IIRC:

Trav, You have to consider

For impact wrenches they usually assume 25% duty cycle.
9CFM is the average air consumption assuming 25% use time.

so its max consumption can be much higher 35CFM or so

 

[Trav]

I understand that but impact guns rarely see 100% duty cycle like say an air grinder or DA sander although on a real tight bolt it can run awhile. Its rare that using an impact alone for a few bolts kicks my compressor on.
You are right though for over 20 CFM constant 3/8 is too small for anything over 15ft I would guess.

 

[Rand]

Originally Posted By: Trav
I understand that but impact guns rarely see 100% duty cycle like say an air grinder or DA sander although on a real tight bolt it can run awhile. Its rare that using an impact alone for a few bolts kicks my compressor on.
You are right though for over 20 CFM constant 3/8 is too small for anything over 15ft I would guess.


I dont necessarily think 3/8 is too small with some high flow fittings and 25ft of hose.

You can always somewhat compensate by turning up the psi to 115 vs 100

I see your point an air sander etc that is 100% duty cycle for long periods REALLY eats up the air much more than an impact..

I was just mentioning for the whole "pressure drop" type situation that it uses a ton more air than 9-10cfm.

I wouldnt dare use a higher psi with some of my cheap tools like air blow guns(150psi vs 100psi rated)
but an impact shouldnt be much issue cranking it above the rated pressure.

 

[Trav]

Aircat claims up to 120 psi on the impact guns so a little higher pressure than 90 psi probably isn't going to cause any problems.