Compressors and rust?

[julianf]

I've just been looking at drain valves, and having some trouble with the logic.

Obviously water condensates on the inside of the tank, slips down the sides, and pools in the bottom.

...to then be let out of the drain eventually.

What I can't see is how frequency of draining will make any difference at all to how quickly the tank rusts.

If you drain the sump once every hour, the walls of the tank will be wet with condensation, running down to the sump, to be drained very soon.

If you drain the sump once a month, the walls will still be just as wet or otherwise with condensation. The only difference is more water in the sump.

Either way, every single cool surface inside that tank is going to be beading with water.

So what's the thinking behind auto drain valves?

Thank you.

 

[tigdlo]

https://www.google.co.uk/search?q=f...VdVRUIHZ9KB_0Q_AUoAXoECAcQAw&biw=1366&bih=654

This seems to show they mostly fail at the bottom where the water collects, you can make out mangled axles and feet in the pictures.

Perhaps they rust more where the water collects.

 

[optima21]

I had one that rusted though, it wasn't catastorphic failure like those, just a pin hole, and then it took me ages to find out where it was coming from.

Ive got an auto drain valve on mine when the pressure in the receiver drops to less than 5psi

from the valve in clarke air filter

https://www.machinemart.co.uk/p/clarke-cat152-14-mini-air-filter/

 

[Submariner1]

I've just been looking at drain valves, and having some trouble with the logic.

Obviously water condensates on the inside of the tank, slips down the sides, and pools in the bottom.

...to then be let out of the drain eventually.

What I can't see is how frequency of draining will make any difference at all to how quickly the tank rusts.

If you drain the sump once every hour, the walls of the tank will be wet with condensation, running down to the sump, to be drained very soon.

If you drain the sump once a month, the walls will still be just as wet or otherwise with condensation. The only difference is more water in the sump.

Either way, every single cool surface inside that tank is going to be beading with water.

So what's the thinking behind auto drain valves?

Thank you.

I wondered about that too.
On mine the drain is near the end, but not at the end.

If drained slowly little water came out.
After the 3rd fill I drained it quickly and with a light shining on the gushing air you could see water droplets.

my question is .... if drained fast, will it pull the water from the sloped end i.e. 60mm and throw it through the drain?
Or will there always be some water in the end. I.e. should one tilt the tank as its nearing the end of the drain? ( that would be a pain)

 

[grim_d]

I think I drain mine once a year.....if I remember.

 

[Gareth J]

Without a drain valve, you'd eventually run out of capacity. Perhaps that's the main reason rather than to stop rust.

 

[daleyd]

I'd guess its as much to do with getting rid of any water in the tank so it doesn't come out in your airline as much as anything else.

 

[Morrisman]

If you don’t drain it, you will eventually have no air storage space, but different places will give different humidity, thus different amounts of condensate. Essentially you don’t want any water inside it, there’s no reason for it to be there.

My old compressor was in the loft of my garage, hardly had a drop came out of it whenever I checked every few weeks, but it wasn’t in use all day every day.

A general workshop ‘shop air’ compressor needs an auto drain because “I thought somebody else was doing that”....

I bought a big old twin cylinder unit off a mate of mine years ago, and couldn’t believe how heavy it was. After it had been in my garage a while i fired it up, drained the tank, and watch for half an hour while defrosted ice ran out the bottom.

He had had it for years, but had no idea you had to drain the tank.

 

[Matchless]

I wondered about that too.
On mine the drain is near the end, but not at the end.
View attachment 257619
If drained slowly little water came out.
After the 3rd fill I drained it quickly and with a light shining on the gushing air you could see water droplets.

my question is .... if drained fast, will it pull the water from the sloped end i.e. 60mm and throw it through the drain?
Or will there always be some water in the end. I.e. should one tilt the tank as its nearing the end of the drain? ( that would be a pain)

the drain may have a tube to the bottom, would work if drained with a little pressure in the tank?

 

[grim_d]

I'd guess its as much to do with getting rid of any water in the tank so it doesn't come out in your airline as much as anything else.

I've a nice big norgren reg that sorts that out for me.

Just encouraging my laziness

 

[brightspark]

https://www.google.co.uk/search?q=f...VdVRUIHZ9KB_0Q_AUoAXoECAcQAw&biw=1366&bih=654

This seems to show they mostly fail at the bottom where the water collects, you can make out mangled axles and feet in the pictures.

Perhaps they rust more where the water collects.

in all my life of seeing leaky tanks theres no way they burst open like that the rust pits just start leaking and pinhole in the odd spot when they get corroded on the bottom the large comp tank I have gets emptied possibly about every 6 month if I remember it gets used regular and id probably get a pint of water out of it when I do empty it

 

[My Old Landy]

ooops! I haven't drained mine since I bought it two years ago come to think of it, I didn't drain the last one and that lasted around 10 years before the motor died. Probably should take better care of them

 

[tigdlo]

At normal operating pressure I dont beleive they do, I think the ones in the photos have likely been over pressurised, but I think it shows the weakest point.

 

[skotl]

I must be the only person on this forum to do so(!), but I open the drain valve every time I finish up for the day and then just leave it open. Then I tighten it up the next time I use it - seems pretty easy

Spoiler: Added bonus

The five minutes it spits air out after I open the drain doesn't half worry the neighbours

 

[Submariner1]

I must be the only person on this forum to do so(!), but I open the drain valve every time I finish up for the day and then just leave it open. Then I tighten it up the next time I use it - seems pretty easy

Spoiler: Added bonus

The five minutes it spits air out after I open the drain doesn't half worry the neighbours

I was going to do that, then realised the anti-vibration, sound proofing mat it sits on dents where the feet are and the drsin is close to the mat ... so spits wet air all over the feet brackets a d I guess would well in the dents of the mat.
So I am looking for some Clear tubing to divert the released air.