DIY Compressed Air Dryer

[olmasters]

Hi Guys,

I've seen various threads online/youtube postings of peoples home made air dryers recently. I'm looking to use my compressor to spray and sandblast with occasionally, so this seemed like a good project.

This is only for hobby use, so I cant justify buying an expensive air dryer, although using something to help condense the compressed compressed air before using drip legs/water traps seemed like a good idea.

I've seen many people with smaller compressors (mine is a 4hp unit) connecting the compressor pump to a vehicle ac condenser radiator, then through water traps, allowing most of the condensate to be removed before allowing the air to enter the tank.

I made a wheeled frame for my compressor over xmas to allow it to be more mobile and enable a similar setup to be attached to my unit. See details of the planned dryer setup below:

For my application a mondeo condenser seemed to be a good fit, the inlet and outlet ports were in a great location and the unit was of a sensible size. Although after unboxing the unit, and just attempting to blow through it, it seemed seriously restrictive (see the air path below) and had a big pressure drop across it.

I know others have used similar systems to this on their compressors and have had good results (I've not heard of any popping!) so just wanted to get a second opinion. The compressor pump kicks out a lot of air, and I'm concerned the condenser might become damaged due to the large pressure drop/the tank will take ages to fill/place too much strain on the pump.

Would I be better off creating a more basic version just out of 15mm soldered copper pipe instead? I know this may not be as efficient, but I could use 14m or so of copper pipe quite easily, have a minimal pressure drop, great flow rate as well as having something more durable too?

I really just wanted to gather some more expert advice on this project. I'm now thinking the copper pipe route would be safer and probably provide something more durable over time too. Im sure the majority of you have far more experience than myself though, so if you can share a bit of advice on the topic that would be great!

Many thanks,
Ollie

 

[SmartWerks]

I'm starting my copper pipe air lines this week. I plan on making my diy dryer from piping using the up and over system.

http://www.mig-welding.co.uk/forum/threads/copper-piping.52164/

be interested to see how you get on, I've not heard any horror stories and I few guys on another forum I use have similar set ups to your plan.

The condenser looks new, how much did that set you back?

 

[rtbcomp]

I would be inclined to go for vertical pipes rather horizontal - the water can drain much more quickly.

 

[SmartWerks]

And let gravity help, the air will go up and over with the water less inclined to.

 

[dannyp]

for blasting trying to dry air dosent 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 recon you'll struggel to do that. for paint it's not really dry enough, mosture will still condense out on cool pannels 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 useing a refigerant dryer tha i got with the compressor and a dessicant one after it for dry air. its supriseing the dessicant still finds moisture after the refgerant dryer

 

[rtbcomp]

You could have two serpentine coils in parallel rather than one long one, that would reduce the air speed in each tube and give more time for moisture to condense.

For blasting the problem is air temperature rather than moisture. Blasting efficiency drops off as air temperature increases. If I have any stubborn paint to shift I try to do it 1st thing in the day when my air is still cool.

I would be inclined to go for vertical pipes rather horizontal - the water can drain much more quickly.

You will have to provide a pipe across the bottom to collect the water though, otherwise the air will bubble through the condensed water and collect moisture.

 

[normspanners]

This is an idea I was going to employ for my system.

If as rtb says if you made a cooler rad within your 'delivery pipe' and used vert pipes, but in 22mm with 22/15/22 tees at the bottom with several vert/ down 15mm legs off the tees about 150mm long then form a horizontal 'manifold pipe/ collector' from 15mm tees and interconnecting pieces of pipe etc, the manifold collector pipe would be blanked at one end and have a slight fall to the open end, so that the main flow of air doesnt go through it, at the open end of the collector turn it down to a single 1/4. compression connector.
The main air flow from the head would enter the top of one end of the rad and out to the nrv through the top of the other end, passing through the vert flow pipes, the water should condense onto these side walls and the condensate would run down the 22vert's and out though tees into the 'still air/ condensate' manifold collector pipe. keeping this mix out of the main flow, then the condensate/water would run down to the compression 1/4 fitting.
Now remove the unloader pipe and blank the connector in the NRV, and plumb the onloader pipe into the 1/4 compression at the end of the rad.
This will do two things give you a 'soft start' larger low pressure area to help the starting of the pump, cool the air and get rid of condensate which would be expelled each time the compressor gets to pressure.
OK there would be a little wasted air each time the compressor cuts out, but there would also be , if you employ an auto drain valve.
Possibly under a minute of pumping time to get up to tank pressure ? but worth it to have drier air.?
if you mounted this as you propose on the belt guard the air movement would help keep cool air passing the rad.

 

[Wayne.]

 

[Farside]

I'm seriously looking at that type, instead of messing around with T-pieces, as I'd previously thought of doing.
However, there seems to be a shortage of the type of AC rads seen in the video, this side of the pond, with the more common type available cheaply for European cars being of the cross-flow and I assume fairly low pressure design, like this, from a Volvo XC70

Certainly, I wouldn't trust the really cheap ones to hold pressure and the one I show might do it, but the continuous-pipe one shown in the video is the one to get, I would think.

 

[Farside]

Can't edit the message, but here's an addendum..
From what I can see, normal car a/c works at 250 - 300psi on the high side 'twixt compressor and condenser, so it looks as though these types of cores will take workshop air, no problem. It's just a lingering distrust of what seems to be conventional radiator core construction, but I suppose these are better built units.

 

[Wayne.]

I will be doing mine the same way as the video i posted only using a bigger second tank if i can find one local cheap

 

[anto44]

I seen a rad the exact same as the one in that video in a scrapyard recently. It was actually a bit bigger than the one in that video. It was fitted to an aircon unit like what you'd see at the back of a supermarket. I didn't take much notice of it at the time, its only after reading threads on here over the last few days that i've thought about building one. I'll be in the same scrapyard on saturday, if it's still there I'll take some pics and measurements and see if i can find a make and model of it.

 

[Wayne.]

Thanks i'm sure that may be of help to someone

 

[Wayne.]

Another way using an old oxy bottle

 

[brightspark]

Another way using an old oxy bottle

that will only work while the air is cool in the pipes and tank -bottle as soon as it warms up moist air will carry on through . it delays the inevitable though

 

[Wayne.]

Got an empty oxy bottle in the garage but the tought of taking a drill to it even though it has been empy for over 4 years is putting me off lol

 

[brightspark]

Got an empty oxy bottle in the garage but the tought of taking a drill to it even though it has been empy for over 4 years is putting me off lol

well its a lot safer than drilling a propane bottle if its empty

 

[Wayne.]

I've already cut a propane bottle after runing water through it a few times i may give it a go

 

[dannyp]

if the bottel is one from the british company of oxygen just beware the valves shutoff with some pressure still in the bottel, so drill a small hole first to let the rest of it vent down ( it's not much pressure but just enough to provoke brown trouser syndrome, when it starts hissing after you've buryed the 9" grinder into it

 

[skotl]

Another way using an old oxy bottle

Oooohhh... I like that. I've an old argon bottle that I could use for that, and without the, ahem, excitement of cutting into a oxy bottle.

Might give that a shot tomorrow...