Optimum Air Flow Of Components Used In Air Supply System?

[Pollys13]

My compressor displaces 397 litres/minute (14CFM) The maximum pressure I
will be using is 50 psi, the air is introduced to the system at 90 psi and passes through a couple of regulators, one drops the pressure to 65 psi the other to 40 psi.

These regulators are shown in the attached photo.

I've bought the correct connectors for the part of system I've worked out how to connect so far.
Most of these are 1/4" BSP, connected into 3/8" ball valves and a 1/2" NPT adapter.
Details of the connectors I'm using are a bit later in this post.

The connectors I've bought or ordered are shown by the green dashed line in the photo
This I'm using as a template for the arrangement of the component parts for my air supply system.

I'm wondering though if how I've connected up will allow for the optimum
correct air flow?

The air line had an ID of 13mm one end of this is connected to the compressor using a 1/2" x 1/4" union the other end introducing the air supply also has a 1/2" x 1/4" union.
This then fits via a 1/4" x 3/8" reducing union into a 3/8" ball valve.
The ball valve is then connected via an NPT adapter 3/8" BSP x 1/2" NPT
to the 1/2" NPT water trap.
The other side of the water trap is connected to a 3 way 1/4" BSP tee
via another NPT adapter this time 1/2" NPT x 1/4" BSP
This tee is connected by a 1/4" hex barrel to the first Chinese regulater which has a port size of
1/4" BSP.
The other side of this regulator has a 1/4" BSP 180mm extended nipple fitted to it
This runs into a 1/4" BSP elbow
To fit into this I've bought a 1/4" x 3/8" adapter
this fits into another 3/8" ball valve.
Going into the ball valve I then have a hose tail male 3/8" bsp x 1/4" hose ID
I connect the air line that came with the pot to this.

Am I going to be getting the correct, optimum air flow using the 1/4" regulators
and 1/4" pipe and connectors, or do they restrict the air flow too much?
Should I replace the regulators with 1/2" ones and 1/2" pipe and connectors?
Cheers.

 

[Shox Dr]

The bigger the internal dia, the better, as while you may be achieving the desired PSI, you'll not be getting the CFM.

 

[rtbcomp]

I use 1/2 regulators and 15mm copper pipe in my system and it works fine for blasting.

Flow depends on area, if you double the diameter of your pipes you quadruple the area.

15mm has an area of 22/7 * 7.5 * 7.5 = 176 mm²

22mm has an area of 22/7 * 11 * 11 = 380 mm²

1/4" has an area of 22/7 * 0.25 * 0.25 = 0.19 in²

1/2" has an area of 22/7 * 0.5 * 0.5 = 0.78 in²

Now you've built it I'd try it. Increasing the pressure will increase the flow.

 

[Pollys13]

The bigger the internal dia, the better, as while you may be achieving the desired PSI, you'll not be getting the CFM.

OK, so if I get the PSI I want, how is not getting the CFM relevant?

 

[Pollys13]

I use 1/2 regulators and 15mm copper pipe in my system and it works fine for blasting.

Flow depends on area, if you double the diameter of your pipes you quadruple the area.

15mm has an area of 22/7 * 7.5 * 7.5 = 176 mm²

22mm has an area of 22/7 * 11 * 11 = 380 mm²

1/4" has an area of 22/7 * 0.25 * 0.25 = 0.19 in²

1/2" has an area of 22/7 * 0.5 * 0.5 = 0.78 in²

Now you've built it I'd try it. Increasing the pressure will increase the flow.

Do you mean increasing the pressure on the master pressure regulator on the compressor itself?
Thanks.

 

[Pollys13]

The bigger the internal dia, the better, as while you may be achieving the desired PSI, you'll not be getting the CFM.

Does not getting the CFM, does that mean the compressor has to switch on and off more frequently?

 

[brightspark]

getting the full cfm means simlar to water in a pipe. the larger the diameter pipe the more water flows through it [volume ]even though the pressure is the same in a small bore pipe or a larger one .

 

[Pollys13]

getting the full cfm means simlar to water in a pipe. the larger the diameter pipe the more water flows through it [volume ]even though the pressure is the same in a small bore pipe or a larger one .

OK.

 

[Pollys13]

The bigger the internal dia, the better, as while you may be achieving the desired PSI, you'll not be getting the CFM.

Does not getting the CFM, does that mean the compressor has to switch on and off more frequently?

 

[Gareth J]

Got some bits to play with there? Try it.

There's ever increasingly complicated maths involved in working out the flow through a system to any degree of accuracy. In a one off like this, just over engineer and test it.

You can get more air to flow through a system by either decreasing the resistance (larger bore) or upping the pressure. You have the advantage of needing fairly low pressures at the end point so you can just up the pressure in the line to punch more flow through. Not efficient, but easy to do.

As I understand it, your setup has 1/4" bore connectors at certain points, you're not going to get very high volume, very low pressure through these so you'll probably need to either run a higher pressure through them or if they're at your end point and need to be at 40psi, you may need to upgrade to a bigger one.

 

[Pollys13]

Got some bits to play with there? Try it.

There's ever increasingly complicated maths involved in working out the flow through a system to any degree of accuracy. In a one off like this, just over engineer and test it.

You can get more air to flow through a system by either decreasing the resistance (larger bore) or upping the pressure. You have the advantage of needing fairly low pressures at the end point so you can just up the pressure in the line to punch more flow through. Not efficient, but easy to do.

As I understand it, your setup has 1/4" bore connectors at certain points, you're not going to get very high volume, very low pressure through these so you'll probably need to either run a higher pressure through them or if they're at your end point and need to be at 40psi, you may need to upgrade to a bigger one.

OK thanks,
You say, " You have the advantage of needing fairly low pressures at the end point so you can just up the pressure in the line to punch more flow through. Not efficient, but easy to do. " You say increasing the pressure isn't efficient, does increasing the pressure involve more wear and tear on the compressor, has to turn itself on/off more frequently to fill up the tank?
Cheers.

 

[Gareth J]

Not necessarily, just means it will be working harder as having to pump to a higher pressure.

Get the smallest fitting you are using and plumb it in directly to the compressor. let the compressor run and see what back pressure the pressure vessel reaches. If it goes over 40psi you know your fitting is too restrictive to let you get the most out of your system.

Did iI read this was for sandblasting? 40psi seems I bit wimpy, unless it's very delicate work surely higher pressure will be better. Like 3x higher.

 

[Pollys13]

Not necessarily, just means it will be working harder as having to pump to a higher pressure.

Get the smallest fitting you are using and plumb it in directly to the compressor. let the compressor run and see what back pressure the pressure vessel reaches. If it goes over 40psi you know your fitting is too restrictive to let you get the most out of your system.

Did iI read this was for sandblasting? 40psi seems I bit wimpy, unless it's very delicate work surely higher pressure will be better. Like 3x higher.

 

[Pollys13]

Hi,
Is for surface etching glass and multi stage carving glass. " Get the smallest fitting you are using and plumb it in directly to the compressor " Do you mean connect a fitting to the quick release coupler on the compressor part of the manifold thingy next to the dials?
" let the compressor run and see what back pressure the pressure vessel reaches."......... How to I do I go about doing this?
Peter.

 

[Gareth J]

ah right, maybe that explains the low pressure requirement. not something I've ever done.

Do you understand why I suggested you try the test above? the "how to" should be straight forward if you understand why you are doing it.

 

[Pollys13]

" Do you understand why I suggested you try the test above?" Yes I think so.
" Get the smallest fitting you are using and plumb it in directly to the compressor. "
Do you mean take the end nut off on the end of the receiver and then fit a 1/4" fitting into that end using a reducing bush, then run the test?
Cheers.

 

[Gareth J]

" Do you understand why I suggested you try the test above?" Yes I think so.
" Get the smallest fitting you are using and plumb it in directly to the compressor. "
Do you mean take the end nut off on the end of the receiver and then fit a 1/4" fitting into that end using a reducing bush, then run the test?
Cheers.

Then yes, just bodge the smallest fitting you are planning to use (1/4"?) into the air tank any old how. I don't know your exact setup or what adapters you have lurking around (nor do I want to) so long as that fitting is the only opening to atmosphere and there isn't anything more restrictive between it and the tank you can try it.

If the tank charges up past 40psi, you KNOW you wont be able to get the max CFM out your system using air at 40psi. whether or not you need the max CFM is another question. This should tell you if things are going to be fine, close to being ok or way off though. Get out to the shed and start tinkering!

 

[Pollys13]

Then yes, just bodge the smallest fitting you are planning to use (1/4"?) into the air tank any old how. I don't know your exact setup or what adapters you have lurking around (nor do I want to) so long as that fitting is the only opening to atmosphere and there isn't anything more restrictive between it and the tank you can try it.

If the tank charges up past 40psi, you KNOW you wont be able to get the max CFM out your system using air at 40psi. whether or not you need the max CFM is another question. This should tell you if things are going to be fine, close to being ok or way off though. Get out to the shed and start tinkering!

I have a Wolf Dakota 100 compressor has quick release couplers see attached photo. I have a 1/4" fitting that plugs into the coupler.
I wil try the test in the morning and get back to you. Since I've had the compressor I only switched it on once for a few minutes to make sure it worked, then switched off and undid the drain valve. Will look at manual, do I need to set the dials to anything? Shading glass can go as low as 5 psi won't show up on the dial.
I'd be lost without the help and forum peoples advice, thanks loads to you and everyone.

 

[Gareth J]

Just plug a quick release connector into one of those couplers? they're 1/4" right?

I've just had a thought, this seems like it might be a really low energy affair and you might be drastically over thinking things. Do you know roughly what CFM range you're going to need? what size is the nozzle for the blast gun?

 

[Pollys13]

Just plug a quick release connector into one of those couplers? they're 1/4" right?

I've just had a thought, this seems like it might be a really low energy affair and you might be drastically over thinking things. Do you know roughly what CFM range you're going to need? what size is the nozzle for the blast gun?

I have a 20 gallon pot.
" Just plug a quick release connector into one of those couplers? they're 1/4" right? " Yes 1/4"
" Do you know roughly what CFM range you're going to need? what size is the nozzle for the blast gun? "
Just looked through my books,

Air Required For Continuous Use With New Nozzle

Look at attachment as following didn't line up when posted message.
Nozzle Size CFM at 40 PSI CFM at 60 PSI CFM at 80 PSI Compressor size at 80 PSI
1/16" 2 3 4 2HP
3/32" 5 7 9 3-5HP
1/8" 9 13 17 5HP
Blasting Pressures.
Note: These comparisons are for standard size blasters. Pressures will vary in work situations.
For example, you may need to set a pressure blaster to 5 psi when carving a very small area
or up to 60 psi for shading a large area.
Surface etching = 30-40 psi
Carving = 35-45 psi
Shading = 1-5 psi
Average nozzle size for standard blaster =3/32" diameter

Air volume required = 5cfm @ 40 psi