Rust in compressor

[cathasatail]

Hi,

 

I noticed today that there was a "sloshing" sound coming from the air tank of my airbush- a quick shake later brought this into the moisture-trap:

 

 

 

 

 

So a few questions:

-presumably it's rust and water?

-should I therefore drain the tank from the valve at the bottom?

-Is it still safe to use, will there be any breach in the pressure vessel?

 

Thanks,

Sam

 

 

 

Edited July 6, 2017 by cathasatail

[cathasatail]

 

Well, i've just drained the tank- the volume of fluid was 1 and 1/2 tin cans worth- a high density of rust and a thick layer of sediment clogging everything up now.... So it looks like it's game over for my first ever compressor (a foxhunter make)

 

So, lesson learned- always drain the tank regularly......

 

Sam

 

Edit^2:

I would just like to formally apologise for swearing: this is completely out of character and there is absolutely no excuse for it. Sorry

Edited July 6, 2017 by cathasatail
no swearing pls

[Jetblast]

-presumably it's rust and water?

Yes.

 

-should I therefore drain the tank from the valve at the bottom?

Yes, although you might find that little comes out as the drain plug may be blocked with sediment - if that's the case, depressurise the tank, remove the drain screw completely & stick something like a fine screwdriver or a bent coat hanger into the hole to clear it.  

 

-Is it still safe to use, will there be any breach in the pressure vessel?

It should be, but who knows really. Rusty water being pumped up into the regulator bowl suggests that the water level in the tank is close to being on level with the tank of-take which suggests that condensate has been accumulating for some time?

Best practice is to drain the tank via the drain screw at the end of every session where you will get a little bit of moisture, but not enough to make a big mess. Failing at the end session I would advise once a week or so at minimum. 

[Brundledonk]

That's a nightmare mate I gues shaking it allowed the gunk to make its way up through the airline into the trap. Did the crud make it through to your airbrush too ?

 

i saw this and went straight down and emptied mine, I do it pretty regularly but haven't for a few weeks and was Suprised how much I got out of it.

 

hope you can salvage yours without too much trouble

 

Pete

 

 

[cathasatail]

15 minutes ago, Brundledonk said:

That's a nightmare mate I gues shaking it allowed the gunk to make its way up through the airline into the trap. Did the crud make it through to your airbrush too ?

 

i saw this and went straight down and emptied mine, I do it pretty regularly but haven't for a few weeks and was Suprised how much I got out of it.

 

hope you can salvage yours without too much trouble

 

Pete

 

 

 

Thankfully I had everything disconnected at the time, I happened to knock it over and after hearing a sloshing sound my first thought was "gosh, that's an awful lot of water (I have had a moderate amount build up in the condensation trap before, which I always take care to drain directly from the trap).

I tipped it upside down to try and get it to drain out and so began the appearance of the rusty solution (note: I have never disconnected the trap before today and I have never been aware of the need to drain the air tank- until now...). This has coated the inside of the trap, despite attempts to rinse it separately with water. As I mentioned above some 1 and a half tin cans-worth of rust solution was drained (this time in the correct manner!) along with a sizeable amount of rust sludge.

 

I'm not entirely sure as to whether it is safe to hold pressure; I know one should be on the look out for confirmation bias but there are no apparent abnormalities with the tank, the seals or any of the piping leading from it. The major concern is regarding the degradation of the tank itself- I would suppose that a rapid depressurisation event has the potential to be very dangerous indeed. Maybe I'm being over-cautious: just finished A-level chemistry and as an avid space-geek i'm aware of the dangers of pressurised tanks failing suddenly.

 

-So, plan of action: I shall leave it to dry overnight with everything disconnected and cautiously try to pressurise it in the morning. Hopefully, it should be recoverable after I've cleaned the trap fully

 

Thanks,

Sam

Edited July 6, 2017 by cathasatail

[Steve Noble]

I don't think your compressor is ruined. When I drain mine I get a lot of oily liquid out from the drain plug. I imagine the inside has gone rusty because of the accumulation of water inside. Now you've got rid of the water I'm sure it will be fine and soon dry out.

[theplasticsurgeon]

With mine the drain valve requires the compressor tilting by about 15degrees to make it the lowest point.

I open that drain every session, a bit of frozen condensation , but nothing like your photos. My compressor is about 30 years old.

I'd remove the drain plug, and switch it on (outside), the pressure will push all the gunge out.

From what you've shown, there's no reason to think that the reservoir is damaged or compromised.  A colleague once suggested that I get mine tested at a scuba centre - instead I let the first charge  take place with me somewhere else

 

Edited July 6, 2017 by theplasticsurgeon
Photo

[Brundledonk]

its normal to have rusty water come out when you drain the tank on these kind of hobby compressors as they aren't treated inside, mines just about a year old and even though I drain it often you can see how rusty it is. If yours isn't ancient then I would have thought the integrity of the tank is ok, I would be more concerned about making sure there is no contamination able to get up the hose and into your brush.

 

i wouldn't worry about drying it out as it will get condensation inside the tank as you are using it, just make sure you get into the habit of emptying it regularly and you will be ok.

 

but I fully understand your concerns about compressed air cylinders and safety, years ago a place I worked had a couple of huge ones that run the glass cutting benches and machinery on the sealed unit line, they were tested regularly for certification and when they guy came to check he always stated how destructive a failure of a tank could be.

 

iirc there was always a bit of rusty water when they got emptied at the end of the day

 

Pete

[cathasatail]

Right, thanks for the advice chaps

 

Today I've drained the tank fully again of any leftover moisture. I then washed out the trap separately, only to find that the seal between the air tank and trap was leaking- some vaseline and PTFE tape later and it's sorted (although now my trap sits at a 45 degree angle for some reason, even without any tape or sealant! (not that it particularly matters to me)

A few sprays of water in the airbrush and thankfully no rust residue at all! Huzzah!

 

I've been gradually pressurising it in increments, still have yet to work up to the auto-cutoff limit but that rarely kicks in when i'm spraying continuously. I'll make another post here if anything else goes askew.

 

Thanks,

Sam

 

Edited July 7, 2017 by cathasatail

[Beardie]

The reason your trap is now sitting at an angle is because of how they are sealed. Typically, and this would have been the case in the factory, they use a special sealant liquid which sets and seals airtight at the right position rather than as far in as  the threads will wind. I use Flomax FM42 Hydraulic sealant when I am reassembling my air joints. It's not that cheap but sets up really well. For a small hobby compressor, especially one that doesn't reach a particularly high pressure I don't think corrosion is too much of a worry for the integrity of the pressure vessel. An explosive failure would require a fracture in the vessel at pretty high pressure. These tanks are welded mild steel by the looks of them rather than cast iron and so will bend/deform rather than crack and go bang. If there is no deformation of the exterior of the tank or signs of corrosion on the outside I am guessing there is no real harm done.