Pressure question

[Steelej]

Hi guys,

Quick pressure question, just got my compressor(airmaster 14/60) the other day and hooked it upto my spray gun(devilbiss GTI pro) to check it all out. So it all works, but one thing I noticed, to get the 2 bar that the gun needs at the gun the output pressure at rhe compessor regulator is at around 7 bar, should the pressure drop be that much?, i'm using a 10m hose 8mm diameter I think. Sorry if these are daft questions, first time i've ever used a compressor,

if I used a shorter hose would the pressure drop be less?

Or if I used a larger diameter hose would the pressure drop be less?

All fittings are 1/4", just concerned if I ever need more than 2 bar with the max working pressure of the compressor at 8 bar what I would need to do.

Thanks and again sorry for the daft questions.

John.

 

[the snooper]

sounds like you are trying to achieve the pressure with the trigger squeezed which is not the way to do it

 

[eil]

sounds like you are trying to achieve the pressure with the trigger squeezed which is not the way to do it

Its the way I set the pressure for mine, how do you set it.

 

[the snooper]

pressure is set with the trigger closed

 

[eil]

I use a 10mm air line to feed an air fed mask and the gun,the pressure at the reg on the wall is around the same pressure as you say about the 7 bar if I remember correctly, thats with the gun trigger pulled.

 

[the snooper]

you will need higher pressure due to the mask being on the same airline

 

[eil]

you will need higher pressure due to the mask being on the same airline

Yes of course, but how do you set the pressure to get 2bar at the gun.

 

[the snooper]

ive always set it at the regulator never used a guage on the gun but just been reading and some say trigger pulled some say not so dont know for deffinate which way is right ive never done it with trigger pulled nor any of the painters i know

 

[piman]

Hello snooper,

I've always set the pressure with the trigger pulled. Static pressure is meaningless as pressure drop from static to active varies with the airline installation (as per the original question). Your set up may give a 2 bar drop for instance and mine might be 4 bar, giving a different pressure at the gun when spraying.

Alec

 

[eil]

Personally I would add another 1/2" bsp regulator on the end of the tank and use a 10mm airline, and not bother with the reg thats fitted to the compressor as most of them are restrictive. It appears that you are not getting the volume of air needed to the gun.
To answer your question on the hose size, A shorter hose like a larger bore will give you less pressure drop.

 

[Chipper]

Seems that some guns drop a lot less with trigger pulled, like my JGA drops maybe 4-5psi, HVLP mini one similar, fullsize Iwata HVLP drops loads. It'd need a crazy input pressure to get 30psi with the trigger back. Did wonder about this as the fullsize HVLP thing was new to me, but found articles that said conventional, trigger pulled, but HVLP, inlet pressure. That made sense otherwise I'd need the wall reg at like 70+psi for the Iwata, so I just dib the trigger to settle pressure and check.
Wall reg stays at 55 for the mask, the Iwata gun reg is around 30.

 

[Steelej]

Thanks guys, good info, yes i'm setting the pressure with the trigger pulled, and I do get enough air for the gun, 2 bar is what's required i was just concerned that if I need more than 2 bar at some point down the road I don't have much more pressure available with the pressure drop i'm currently seeing.

I've had a couple of lessons at a body shop I know and they also set the pressure on their gti's with hvlp cap by pressing the trigger and setting the pressure on a regulator on the gun.

John.

 

[Steelej]

Personally I would add another 1/2" bsp regulator on the end of the tank and use a 10mm airline, and not bother with the reg thats fitted to the compressor as most of them are restrictive. It appears that you are not getting the volume of air needed to the gun.
To answer your question on the hose size, A shorter hose like a larger bore will give you less pressure drop.

Not sure I understand this, the fitting from the compressor is 1/4" are you saying to upsize that to 1/2" then run 1/2" to the gun? The gun fitting is also 1/4".

John.

 

[Steelej]

Another question, so if I cut my 10m hose down to 5m would i half the pressure drop or does it not work like that?

John.

 

[Steelej]

Been messing around with this more today, I removed the quick release coupling at the compressor outlet, connected the hose directly to the compressor and it's reduced the pressure drop by 2, I can now run the output at 5 bar and get 2 bar at the gun. Didn't think the coupling would make that much difference. Does that sound normal?

John.

 

[brightspark]

Been messing around with this more today, I removed the quick release coupling at the compressor outlet, connected the hose directly to the compressor and it's reduced the pressure drop by 2, I can now run the output at 5 bar and get 2 bar at the gun. Didn't think the coupling would make that much difference. Does that sound normal?

John.

they restrict the air quite a bit depending on what tools u are using i use eurocouplings- pcl and also c couplings . c couplings have no restriction what so ever as there full bore

 

[Steelej]

It's actually PCL couplings I'm using, I had one at the compressor and still have one at the spray gun. Wondering if I replaced the one at the gun if i'd reduce the pressure drop even more.

John.

 

[brightspark]

It's actually PCL couplings I'm using, I had one at the compressor and still have one at the spray gun. Wondering if I replaced the one at the gun if i'd reduce the pressure drop even more.

John.

the end of line isnt much of a problem using pcl fittings with a short whip fitted. the main thing is use 10mm pipe close up to where u are using the air then reduce the last couple of meters of pipe to a smaller diameter for ease of use . using smaller bore pipe gives more velocity and less cfm not good more cfm and less velocity using a larger bore

 

[eil]

Not sure I understand this, the fitting from the compressor is 1/4" are you saying to upsize that to 1/2" then run 1/2" to the gun? The gun fitting is also 1/4".

John.

Have a read through this old post might make things a bit clearer for you http://www.mig-welding.co.uk/forum/showthread.php?t=18442

 

[Steelej]

another quick one, is there a better quick connect coupling I could use that may have less impact than the PCL one I'm using at the gun?

John.