Condensation issues.

[davelectronic]

After a long period, I'm close to finishing an air brush compressor. It was originally a retail oiless compressor, but for my use indoors it was just to loud in operation. I replaced the new oiless compressor with two refrigeration compressors, single phase. Along the way I've had a few problems, from adding wheels to the base and it toppling over destroying both relay control boxes. So had to rework an alternative wiring input solution, the unit uses a pressure switch with a high current SPDT relay to control the compressors and solanoid unloader valve. Its all working fine, but where I've used clear braided air line for the output air, I've noticed condensation in these discharge airlines. I was wondering if any of this condensation is likely to find its way back into the compressors ? The compressors are well lubed up with 300ml of compressor oil in each unit. The discharge tubes air descending in there angle as they leave the output port on each compressor. So unlikely to find condensation climbing back up these air lines. But it still remains a wet environment inside these discharge airlines. I'm thinking as the compressor inside has oil around it, it should be fine. But the site of water droplets in the discharge lines doesn't make me feel confident about it. I know all compressors accumulate water in there function, and ends up in the air receiver, and then drained off periodically. So my question is should I need to alter something from the discharge ports, like an add in filter, or is this fine condensation of no significant problem to the compressor units. I know it's a fair way from discharge port back along the internal lines to the output leaf valves and piston. But just can't help thinking this condensation could in theory make its way back to the compressor valves and reciprocating assembly. I know this is a non electrical question, but would appreciate any thoughts on this potential problem. Thank for taking time to read this problem.

[Terry Bites]

https://www.ebay.co.uk/itm/Airbrush-Air-Filter-Airbrush-Water-Trap-Airbrush-In-Line-Moisture-Trap-Filter-/332491715806

[davelectronic]

Thanks for the link, I have these already connected to the airbrush. They came with the airbrush kits, the condensation I'm concerned about is in the airline straight from the discharge port in the compressor. If I'd have used black airline hose I guess I'd of never seen it. Hopefully it won't make its was back inside the discharge output port.

[amyk]

Put an air dryer on the input.

[Kleinstein]

Unless one has extemely dry air, it is normal to get some water condensation in the compressed air. Effectively the RH get muliplied with the higher pressure and in GB it is unlikely to get RH levels below 10%.
The compressor unit itself runs hot (essentially all the input electrical power is converted to heat - even a little more  ) so the condensation mostly happens in the lines or tank. Usually the compressors can handle smal amounts of water.
After turning off the environment in the tank will be relatively humid.

There are some filters / separators to remove most of the water dropletts in the compressed air.

[davelectronic]

Tanks for your replies, relative humidity shouldn't be a problem here in the UK. I was not totally sure that water droplets could find there way back into the compressor. As the discharge lines are descending, I think it probably unlikely any water would reverse back down the air lines. I'm certainly going to look at air driers, to see if there is anything suitable to put between the discharge port and the descending air line. But the unit runs really well for a homebrew set up. Had first try with an airbrush the other evening, and worked as expected. Thanks again for the help.

[Kleinstein]

It needs to be really dry to not get condensation in a compressor. I have seen this in new mexico with a compressor that was active for some 10 years, though not that much run-time. But even there, with extremely dry climate I would expect condensation some parts of the year. I dry day there was 3% RH and <10% RH was the normal case. In GB I would expect more like 50% RH on average and maybe 10-20 % for the yearly low. So definitely expect condensation in a compressor.
If you have condensation at a glass of a ice cooled drink in a room at some 20 C RH is above some 25% and condensation in the compressor is definitely expected.

An air dryer at the input to a compressor is very unusual. The more normal way is a dryer at the output, but this is usually a quite large unit.  Usually the compressors work at some 6-8 bar, while air brush needs some 2-3 bar. So there is some pressure reduction and with sufficient to warm up the air after pressure reduction there is no real need for extra measures. So the usual way is to only have a water separator and maybe some filter and than the pressure reduction.

[davelectronic]

Yes I do have a water / oil separator inline, and a regulator to reduce the air pressure for the airbrush. The compressor on turn on fills the 24 litre receiver, turns off at 120 psi and comes back on at 90 psi. There is an unloader valve solanoid to blow down after the compressor turns off at 120 psi, I think the condensation is something I have to live with. Hot air coming from the compressor, discharged in to cold air lines to the receiver are just going to create condensation. If the unit lasted a few years, I would be happy with that.