DIY Compressed Air Dryer

[GrumpyOne]

I have a hot water tank (about 4' tall, covered in insulation) in my workshop which is unused, I thought about cutting the top off it, putting in a few meters of 15mm copper pipe, soldering the top back on, filing it full of cold water and running my air through that to act as a condenser.
Does that sound like a reasonable idea or am I blethering

 

[Rig Pig]

It depends on how much air you use, it would need a collection pot at the lowest point and a valve to drain it

 

[normspanners]

I have a hot water tank (about 4' tall, covered in insulation) in my workshop which is unused, I thought about cutting the top off it, putting in a few meters of 15mm copper pipe, soldering the top back on, filing it full of cold water and running my air through that to act as a condenser.
Does that sound like a reasonable idea or am I blethering

No that sounds the right idea but no need to solder lid on just make it 'fit' the only thing is the condensate is still traveling in the pipe that is carrying the air, so will make its way into the tank, and then re contaminating the stored air as it blasts into the tank / reservoir
you really need a collector out of the main air stream to work best IMO

 

[rtbcomp]

Best leave the lid off, evaporation will help with cooling. In fact cut the tank lengthways to make a trough - more surface area.

 

[Maker]

for blasting trying to dry air doesn't really work, unless your into serious kit most dryers won't deal with the flow rate by a long way i know mine won't.

cooling the air from the compressor down to ambient is going to help for blasting to a point but I reckon you'll struggle to do that. for paint it's not really dry enough, moisture will still condense out on cool panels or from the pressure drop cooling effect as air leaves the gun. you ether put up with moisture when spraying or get DRY air. I'm using a refrigerant dryer that I got with the compressor and a desiccant one after it for dry air. its surprising the desiccant still finds moisture after the refrigerant dryer

Could one make a desiccant dryer using loads of silica gel packets?

Another way using an old oxy bottle

Are oxygen bottles really 1&1/2" - 2" thick.

 

[normspanners]

Are oxygen bottles really 1&1/2" - 2" thick.

I dont think we could move them if they where !!


One spec

Seamless Tube Oxygen Gas Cylinder

Specification:

Diameter (mm) 219
Water Capacity (L) 40
Length (mm) (ex.valve) 1320
Weight (KGS) 48.5
Wall Thickness(mm) 5.7
Working Pressure (MPa/bar) 15/150
Testing Pressure (MPa/bar) 22.5/225
Material 37Mn

 

[Rig Pig]

commercial dessicant drying systems are available, they are usually tandem units with a switch over so one bank can regenerate as the other one is online.

 

[Maker]

I dont think we could move them if they where !!


One spec

Seamless Tube Oxygen Gas Cylinder

Specification:

Diameter (mm) 219
Water Capacity (L) 40
Length (mm) (ex.valve) 1320
Weight (KGS) 48.5
Wall Thickness(mm) 5.7
Working Pressure (MPa/bar) 15/150
Testing Pressure (MPa/bar) 22.5/225
Material 37Mn

A quick calculation reveals they would weigh more than 300 KGs if they were 2 inches thick.

 

[Farside]

I have a hot water tank (about 4' tall, covered in insulation) in my workshop which is unused, I thought about cutting the top off it, putting in a few meters of 15mm copper pipe, soldering the top back on, filing it full of cold water and running my air through that to act as a condenser.
Does that sound like a reasonable idea or am I blethering

If you had a twin coil tank, one of them for the air (and drain point at the exit of it) and the other coil to be plumbed into the incoming main so it gets an intermittent flow of chilled water from teh ground piping. You could also / instead, hook up the main body of the tank to a chiller, made from ex-freezer or fridge components for dirt cheap.

 

[rtbcomp]

Why not just flow the water through the tank, no need for a 2nd coil and better heat transfer. You could set up a pump to pump the water through a freezer, but if you go to that trouble just run the air through a pipe in the freezer.

 

[brightspark]

just use an indirect tank theres allready a 25mm heat transfer coil pipe fitted inlet and outlet on the lower side of tank just blank off the l;ower waterfeed pipe and fill with water

 

[rtbcomp]

You'd still get better heat transfer using it in direct mode with no 2nd coil.

 

[Maker]

Could you not buy (Or make) a heat exchanger like the one below with the compressed air going through the "tube side" and cold water being pumped through the "shell side" by a welding watercooler (Or a small pump or just a garden tap)?

 

[rtbcomp]

Could you not buy (Or make) a heat exchanger like the one below with the compressed air going through the "tube side" and cold water being pumped through the "shell side" by a welding watercooler (Or a small pump or just a garden tap)?

A multi tube heat exchanger could be made from copper pipe and Yorkshire fittings, but the above design is flawed because

1) you want to remove the hot water from the top
2) there is no means of draining the condensate - A drain would have to be provided at the lowest point in the lower plenum
3) the hot air needs to go in at the top

 

[normspanners]

Well i have just bought 120x 22mm cheap tees off e bay to start making mine copper tube £10 x3 length local
and it will have as mentioned, a drain manifold at the bottom out of the main air flow that will drain each time compressor gets to pressure.

 

[Maker]

A multi tube heat exchanger could be made from copper pipe and Yorkshire fittings, but the above design is flawed because

1) you want to remove the hot water from the top
2) there is no means of draining the condensate - A drain would have to be provided at the lowest point in the lower plenum
3) the hot air needs to go in at the top

Oh yeah, that picture is upside down, I hadn't noticed that. As a simplified version, could you modify a 15x22x22 copper Tee to allow the 15mm pipe to pass right through?

Like this. Obviously this is a very simplified design using only 15 and 22 mm copper pipe.

 

[rtbcomp]

[QUOTE="Maker, post: 614125, ........., could you modify a 15x22x22 copper Tee to allow the 15mm pipe to pass right through?
............[/QUOTE]

Yes, I've done that in the past with 15mm and 10mm. You need to remove the bit in the tee that the through-pipe would normally limit on.

 

[normspanners]

My idea of a cooler using 22mm pipe this could be placed in a water tank if needed or in the flow of cooling air through flywheel

 

[SmartWerks]

My idea of a cooler using 22mm pipe this could be placed in a water tank if needed or in the flow of cooling air through flywheel

View attachment 60227

That's how mine are going to be, simple and apperantly very effective. If i was doing paint spraying I would invest in a proper refrigerated dryer.

 

[rtbcomp]

That looks good - make the manifold from smaller pipe (8 or 10mm) so the air takes the path of least resistance, ie round the bends. Also I'd drop the link between the manifold at the outlet.