Started cooling my compressed air today...

[rcx132]

Today I connected up my compressed air to run through a big rain water butt. I made a copper coil from a 3m copper pipe.

Result? The water trap trapped 5x more water than usual!

My theory is... that the water traps that most people have only catch water that is dragged or atomised in the air. They don't trap water that is evaporated in the air. By cooling the air you're reducing the evaporation capacity. The air drops the water, which then turns to droplets, continues down the pipe and gets caught in the water trap.

If my theory is right then I don't need a drain off in my pipework like people suggest... I can't have one anyway as my pipe travels along my ceiling so it goes up and down too many times.

 

[rtbcomp]

I think you'll still have water in your pipework. If nothing else when you finish for the day the droplets will settle out. Pipework should always be designed with drain points in mind and sloping away from the compressor so droplets and condensation gets carried away with the airflow.

 

[rcx132]

I think you'll still have water in your pipework. If nothing else when you finish for the day the droplets will settle out. Pipework should always be designed with drain points in mind and sloping away from the compressor so droplets and condensation gets carried away with the airflow.

I'm not convinced. Yesterday I disconnected my copper right before the point that it goes up my wall from the compressors, exactly where you'd expect water to be trapped, and nothing was there despite lack of drain valve. I had the same at my last garage, after reading this forum I panicked because I had spots in my air pipes that would blatantly trap water. Dismantled them and nothing...

I reckon the dropped water gets carried along the pipe and then the water trap in the regulator catches it.

After running compressors yesterday I could feel the warm pipe going into the rainwater butt and the cold pipe coming out ツ Before the heat used to travel all the way up 8m of copper and even the regulator at the end was warm !!

 

[Farside]

If you were getting warm air out of the uncooled system it was still carrying a lot of water vapour.
The water in the butt has a far greater heat capacity than the air normally surrounding the pipe, so can be much more effective as a heat exchanger, cooling the air inside much better and taking the moisture out of suspension.
Depending on the size of the butt, and how much air you use, it will eventually heat up but probably not to the point it loses effectiveness, especially at this time of year.

 

[carbon]

I have a small intercooler with an auto drain after it fitted between the pump and the receiver on my compressor. The amount of condensate that collects in the receiver is minimal compared to the amount that had to be drained previously

 

[henry Kadzielski]

^^^^ If you are running for long periods of time (over 1 hour contineous) then even the aftercooler will get warm and the discharge air will contain moisture. This moisture will condense down stream. I have an aftercooled diesel compressor about 120l/sec at 10 bar. My refrigerated dryer stopped as some one had pulled the power out and after about 45 min running had trouble with the grit not flowing through the metering valve correctly. Water had condensed in the line wet the grit and stopped it flowing. Only fix was to restore the power the the dryer, remove the grit metering valve and drop out the wet grit. Once this was done all was back to normal. Aftercoolers work well at reducing water down the line, however a refrigerated dryer will remove two or three times the moisture from the air stream after the aftercooler. If your humidity is low <20% you will probably be ok, however if you are running high pressure and volume it WILL CATCH UP TO YOU. No need to ask how I know.
If you have gotten away with no problems then 'YOU HAVE GOTTEN AWAY WITH IT'. In commercial blasting there is massive attention placed in the removal of moisture in the blasting air, it promotes flash rusting post blasting, which is something all blasters are trying to avoid.

 

[carbon]

Intercooler does have a fan fitted to help reduce the temperature but imagine it's more effective during cooler weather

 

[rcx132]

I find that £20 desiccant drier works fine but gets used up. Now that I've got the heat exchanger submerged in water butt I think it will make the desiccant last much longer.

I'm also going to try mineral desiccant as it's cheaper £2.40/kg and use some indicator paper to monitor when it's used up.

Your right about undried air causing flash rusting after blasting. I blasted two parts one with dried air and one with undried. The undried one was rusted by next day.

 

[rtbcomp]

... I blasted two parts one with dried air and one with undried. The undried one was rusted by next day.

Different materials rust at different rates. I've blasted brake calipers that went rusty before my eyes, I also did some bench ends that only had slight rusting after 13 months.

 

[rcx132]

Different materials rust at different rates. I've blasted brake calipers that went rusty before my eyes, I also did some bench ends that only had slight rusting after 13 months.

OK but the wet air still makes a difference. I used MBX tool to strip most of my body but used media blaster to do the bits that the tool couldn't reach. The bits done with the tool are still rust free a month on. The bits done with the blaster have re rusted.

 

[brightspark]

after u have blasted coat them as soon as possible it also depends on the humidity of that day

 

[rcx132]

after u have blasted coat them as soon as possible it also depends on the humidity of that day

To be honest the bits I blasted were just to test how quickly the blaster can remove the paint and residual seam sealer. I still have some stripping left to do and then I need to time it so I can blast and get paint on asap.