Installing air assist - have questions

[dave hensley]

Hi all,

I've ordered the air assist cone for my VLS 3.5 laser and now need to get air up to my office. The office is located directly above my garage workshop where I have my 17gal compressor, so I am thinking I'll just run piping/air tubing up to the laser from there. If I do this, the length of pipe needed would be close to 25 feet. Should that be long enough for the air to cool or do I need to implement a method for additional cooling?

I assume I also need a water trap and pressure regulator. Having the water trap in the workshop will have it about 14ft below the laser. The regulator I was thinking I'd put in the line just a couple feet shy of the laser.

Also, the piping would be routed through an attic area that is next to my office. Should I insulate the piping in that space?

Or the other option is to purchase a compressor suited for air assist and just keep it in the attic space that is just on the other side of the wall from the laser, putting only about 3 feet away at most. If I go this route, I need some advice on compressors that are intended for air assist so that I can minimize all the other items I'd be using for my standard compressor.

I've read several other posts regarding air assist, but feel I still need some advice. :)

[Dan Hintz]

If the piping run is metal, that should be enough to cool it... if it's just rubber hose, you'll want something extra. Personally, I just run it into a desiccant dryer just after the water trap, both just before the laser. The compressor is in a room with a dehumidifier, so the air it's compressing is pretty dry to begin with.

[Richard Rumancik]

Black pipe seems to be the material of choice for air systems. Make sure that any condensate that collects in the pipe or tube has a place to go, and a place to drain it. The drain should be at the lowest point in the system i.e. below the compressor where you tap off to go upstairs. Also make sure it is plumbed so that moisture doesn't try to back up into the compressor outlet. And of course, don't forget to drain the condensate. Having 25 feet of metal pipe is fine. If it was plastic tubing then probably less moisture will condense out on the inside walls.

Offhand I don't see why you would need to insulate the pipe. The pipe should be large enough that moisture can't freeze and plug the tube. As long as there is flow the warm compressor air would melt any frost inside the tube that accumulates overnight. Seems that you have a "naturally refrigerated air dryer". Running the pipe through cold air will increase the amount of condensation (which is good.)

You should still have a small supplemental air dryer (desiccant dryer) in the room and a particulate filter to make sure nothing gets onto the lenses.

[Mike Lassiter]

You can use PVC water pipe or the pex that comes in rolls from Home Depot or Lowe's which would be much easier to run. You will not be using a hugh volume of air say like an air impact wrench or air paint gun with the laser air assist. I have ran mine using 1/2" PVC water pipe which is in 10 foot sections. I have a Craftsman vertical 220 compressor in a small "closet" in the building our laser is in. When we finished the inside of the building (12'x32') I framed the closet at the opposite end of the building and insulated the walls to help with noise. I have a 3-1/2 hp dust collector I purchased from Penn State modified for exhaust system that recirculates the air so we can keep the temperature maintained in the shop when the laser is being used. I ran the plastic air line to the laser just under the 6" metal pipe that is also ran to the laser from the closet. I have the regulator on the air compressor itself set at 90 psi, then at the laser I have a all in one regulator, moisture trap that is reduced down to app. 40 psi to feed the laser when I use the air assist.

You should also consider including a drop for a air line to allow you to have a air blower on one of the coiled hosed that will let you do some cleaning and so on when you do this. I have that on a tee fitting just before the regulator/ moisture trap at the laser. The blower comes in handy from time to time with "dusting" inside the laser and shop. Metal pipe is bullet proof if you have the ability and tools to run it, but it is much harder to run in some circumstances than plastic, especially if you need a long section of pipe and don't have the space to maneuver it into place. You can bow or bend plastic pipe somewhat to aid in installing it, where metal will not allow that.

I have yet to have any signs of moisture in the moisture trap bowl at the laser. I have everything inside, but moisture is just about always produced in some amount by compressing air. I think in my case the 33 gallon vertical tank with the air supply at the top helps to prevent moisture getting into the air line, and the trap is a precaution that so far has never shown any moisture to be present. I suppose some could argue my setup isn't to their expectations, but it has been trouble free regardless.

[M John McDonough]

I am a plumber and the only thing I recommend is black iron pipe or at the very least copper. Plastic has a tendancy to explode (think hand gernade). Come off the tank with a 90 degree elbo to the side and then into a tee with a line going up and a drip leg hanging down with a plugged shut off valve. The plug can be taken out and the valve opened to drain the system.

[Barry Clark]

I've been using plastic airlines in the shop for ten years. 150 psi daily and never a problem with bursting..

I would think if you're going to run the line through an unheated attic space a condensate trap of some type should be used just ahead of the laser.
The heating cooling cycle of the air through that area may cause condensation in the lines.

JMHO

[dave hensley]

Thanks for the advice everyone! I think I'll price out what it'll cost to use the black pipe. What diameter pipe do I need for this type of application?

Also, I'm going to sketch out the most likely layout and may post that for some feedback. I expect that I'll add two water traps after reading your replies - one in the workshop and one at the laser.

Thanks again! I am sure I'll be back with more questions. :)

[dave hensley]

Alright, here's what I have in my head right now for running the piping for air to my laser. It's not exactly to scale, but it's darn close. This arrangement would give me about 27' of piping.

Is it possible to put water trap and a desiccant dryer in a vertical section of pipe or would I need to add a horizontal section in the workshop for those?

Once I get the piping up to within a few feet of the laser, can I use flexible tubing through the wall to avoid running the pipe through wall? Can I have a water trap/dessicant dyer inline with the tubing or do those need to be inline on the pipe?

Sorry for all the newb questions - I've never had to work with air in this way before. :)


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[Mike Lassiter]

Another consideration is you can use plastic air brake hose used on HD trucks. You buy it by the foot and can get it in 1/4",5/16",3/8",1/2", and 5/8" diameter. You will need to get fittings for this hose also. You can get it at NAPA and truck parts places. That will be much easier to run that any stick pipe and will withstand the pressure fine. It might eliminate having several joints changing from pipe to hose and back which are more apt to leak that the hose alone. Every connection is a potential leak source later. The fewer the better. Water trap like I have has to be hanging "down" and requires bowl drain at the bottom, so it will have to be vertical mounted to work. (on vertical run mount it to wall and use 90 degree elbow in, then 90 degree out going up, which will have the lines offset but allow you to drain the trap) I would think the desiccant dryer would also be the same, as there has to be a way to drain them, and if you don't have the moisture trapped at the bottom of the containment area it could just run on thru the dryer if there's no place to catch and hold it.

[Dan Hintz]

Another consideration is you can use plastic air brake hose used on HD trucks.
Then why not just use a standard rubber air hose?

[Mike Lassiter]

Then why not just use a standard rubber air hose?


You could, but the hose doesn't have the stiffness the plastic line does, and would require more support to keep it from drooping or sagging. The plastic is more resistant to cuts and so on. Frankly, I have also saw rubber hoses develop leaks over time (getting a large blister or bubble due to internal wall defect) were I have NEVER saw plastic air line leak unless someone was welding or using cutting torch and got hot metal on the line causing it to rupture. I guess it really boils down to personal choice, and what tools and abilities you have to work with.

One other thing to consider for plastic (water or air) is the ease that you can make changes later should you need to. Metal pipe will not allow you to bleed the pressure out of the line and cut it with a pocket knife, ratcheting cutter, or saw and add a tee in the middle of a run to add another air source and either glue or tighten fittings back and have the air system back operational in 30 minutes to an hour.
Plastic is cheaper to buy, easier and faster to install, and easier and faster to modify later - and will work. Or you can cut and thread metal pipe, or worse buy a bunch of different length pipe nibbles and couplings and have a zillion joints to deal with. Metal pipe is bullet proof, but you don't HAVE to run the line in metal pipe for it to work and be safe. Skill of the plumber comes in here also. There are certain details that must be address with whatever you use, or else you will have small leaks - mostly common sense stuff. Pipe threads must be sealed with dope or Teflon tape (and enough of it) and joints tightened good. Plastic must be clean and glued right. Poorly glued joints are dangerous under air pressure and can seem to explode when they fail (as was noted above). A good reason to use the plastic air line and screw together fittings if you have doubts about gluing good joints.

[dave hensley]

What about this Rapid Air system (http://www.rapidairproducts.com/index.asp)? Is this similiar to what you're referring too? States up to 150psi working pressure. I don't mind the flexible tubing as I don't have far to run it.

[Mike Lassiter]

here is a link from NAPA online http://www.napaonline.com/Search/Detail.aspx?R=WH_TP16008NA500_0076392391 for 1/2" dia. tubing. As you can see by the copied properties below it easily exceeds pressure and temperature requirements. This is the type of line used on semi trucks that are exposed to the extreme cold and hot driving across the country.


Material : Plastic
Series : TP160 Polyamide Nylon 11
Tube O.D. : .5" (12.7 mm)
Where is Product Used : Flexible Nylon Tubing. Used For Instrumentation; Lubrication & Air Lines; Gas, Chemical & Oil Processing; Low Pressure Hydraulics.
Available Unit Lengths : 500' (152.4 m)
Description : Tubing - Plastic Tubing
Hose Minimum Bend Radius : 4.5" (114.3 mm)
Nylon 11 Tubing Working Temperature Range : -40 To 200 Deg F (-40 To 93 Deg C)
Plastic Nylon 11 Tubing Wall Thickness : .062" (1.57 mm)
Tubing Color : NA
Tubing Maximum Working Pressure : 250 psi (17.2 bar)
Tubing Minimum Burst Pressure : 1000 psi (68.9 bar)
Tubing Pounds per 100 ft : 3.8 lbs (1.7 kg)
Uses Fitting Part #s : Push Connect, Push Connect Flow Controls, Push Connect Plus, Molded Compression

[dave hensley]

Thanks for the link Mike!