Old compressor revival - safe to use tank

[Si_H]

Hi All,
A friend recently gave me a collections of bits which I've put back together into something resembling a compressor.
I'd estimate it's from the 80's/90's, Receiver is branded Draper, motor Red Devil, and the pump I can't ID, but the filter box has a logo on which I think may be Airblok. Looks like this:

From what I can see, seems worth saving.

Anyway, rebuilt the pump and it's moving decent air, but haven't yet connected the tank. I'm a little concerned about whether or not it'll be safe to use.
I've shone a torch in the blow off port and taken a photo at the outlet, and there's clearly some corrosion in there. Photo below shows the drain valve end (I'm going to try and get a scope in the tomorrow to take better photos all over)

Does that look bad? It's been moved around a lot in a car hence the flakes all being at one end.

Tank plate here:

Spoken to a few dive vessel places who will test it for £50-£60, and it seems that basically what they'd do would be fill it with water, pressurise to 1.5x working pressure, and hold it there for a few hours and check for leaks (something I can do at home)
If it passed that test, would you consider it safe to use?
Thanks in advance

 

[hotponyshoes]

A dive place will check internally with a borescope and a ultrasonic thickness gauge if it looks like there are any thin/weak spots.

I would also go over the outside with a wire brush in a grinder and repaint.

If it passed the pressure test then I would personally be more than happy to use it.

 

[gordon stephenson]

A safe way to test is using water for the pressure and not air,

 

[hotponyshoes]

A safe way to test is using water for the pressure and not air,

Its the only safe way.
Also a good idea to cover the thing in a blanket or something for the first go. Any little pin holes can create a jet of water that can do serious damage to an eye!
Make an adaptor to feed a pressure washer into it if you don't have anything else.

 

[Si_H]

Thanks all.
My plan with the water was to stick a hose tail on one of the outlets, bung the other holes with blanking caps, and pressurise a small air space with a bike track pump (I have one that will hit circa 200PSI)
So basically, general feeling is that if it's OK with about 1.5x working pressure without leaks (15 bar) then you'd be happy to use?

 

[knighty]

fill it with water and then blow it up with your bike pump to 200... and leave it a while

maybe kick/knock it a few times too

if it's ok with that then it's good to go :-)

 

[Stingray]

Its the only safe way.
Also a good idea to cover the thing in a blanket or something for the first go. Any little pin holes can create a jet of water that can do serious damage to an eye!
Make an adaptor to feed a pressure washer into it if you don't have anything else.

We used to hydra-test boilers when we done repairs or for their 5 yearly test, 99% of the time We used a test bucket, odd times We use a small electric power hose with pressure gauge and valve but be wary pressure goes from zero to a lot of bar very quickly, a test bucket is more controllable...

 

[addjunkie]

1.5 working pressure is a strength test. And the comment above re the pressure rising very quickly, is really valid,

Check the pressure gauge works in some way before you start pumping.

 

[Stingray]

I use a pressure tester for central heating systems, a cheap Chinese one like below. I've replaced the gauge with one that I can trust though and added a couple ball valves. I tested a tank in the sun once and it scared the hell out of me when after half an our I noticed the pressure had risen from the 15 bar I put in to over 20! Tank held the pressure fine though (inside looked very similar to above pic), but the next one I made sure to test in the shade.

Edit: I think this is the one I have.

We always test pipe spools in the shade or at night, especially when We had recorder on it, looks more suspicious when we had the recorder on it...

 

[Bill Edwards]

As you have the means of pumping the air pressure to 200psi after brimming it with water that's what I would be doing, you then know it's OK.

Make sure the safety valve on the compressor works before putting it into use, in case something ever happens that stops the motor from shutting off.

 

[Si_H]

Cheers for all the pointers guys
I've bought a new safety valve as the one in there was an unknown quantity.
However, I can't shift either the air inlet connection or the shut off switch one to bung them. The inlet looks like a one way valve, so I'm guessing I'm ok to leave that in?

The pressure switch looks like it's connected via some sort of valve that I can't shift either. Is this a one way valve as well?

Basically, as I can't undo either and don't want to resort to lots of force, an ok to just bung the outlet, fill with water, and pressurise? I can't see why not at the moment. My only concern would be damaging the switch, but if that's a one way valve I can't see that being an issue?
Thanks

 

[eddie49]

The air inlet to the tank will have a one-way valve, and also an "unloader" to release the pressure in the feed pipe so the pump does not have to restart against pressure. However, the feed to the pressure switch will just be a short piece of 1/4, 3/8 or 1/2 inch pipe, threaded BSPT at each end. I would suggest trying to apply a small amount of heat to help unscrew it.

 

[Bill Edwards]

As above.

A bigger spanner ought to be enough, they’ll typically have a sealant on the threads but I’ve always shifted them so far.

 

[eddie49]

With its one-way valve, the tank inlet will be OK during your pressure test. On the outlet, there is no valve, and I don't think the pressure switch will like 200 psi. The outlet pipe stub ( "nipple" ) will be threaded into an aluminium casting on the plastic base of the pressure switch. There will be flats for a spanner there. If that does not open, apply heat directly to the threaded boss on the tank, and use a Stillson to unscrew the outlet pipe.

 

[brightspark]

The tank as you call it is really calledl the air receiver and they're designed to have an overload Factor before they burst don't worry go ahead and use it

think you are missing the point . if the tank is well corroded inside he is concerned it may let go . to be honest all I would do is turn it upside down and tap it all the way along the bottom with a ball pein hammer . if the metal is weak and well corroded it will dent if it doesn't its ok. if there are just small rust pits here and there it wont burst they will just leak and blow a bit of air out

 

[Dan93]

Hi, my 250 litre is from 1982, works fine!

 

[rtbcomp]

Cheers for all the pointers guys
I've bought a new safety valve as the one in there was an unknown quantity.
However, I can't shift either the air inlet connection or the shut off switch one to bung them. The inlet looks like a one way valve, so I'm guessing I'm ok to leave that in?

The pressure switch looks like it's connected via some sort of valve that I can't shift either. Is this a one way valve as well?

Basically, as I can't undo either and don't want to resort to lots of force, an ok to just bung the outlet, fill with water, and pressurise? I can't see why not at the moment. My only concern would be damaging the switch, but if that's a one way valve I can't see that being an issue?
Thanks

The device connected to the tank with a thick and thin pipe attached is indeed the non-return valve (NRV), the thin pipe is the unloader and the thick one the air inlet to the tank. NRVs can sometimes leak back to the pump, usually due to the rubber disc (the pastille) inside it being worn or a foreign body trapped in it.

The thing the pressure switch is mounted on is just a short length of pipe, this connects the switch to the tank.

There are some photos and drawings here https://www.mig-welding.co.uk/forum/media/albums/compressors.206/

 

[cheb]

A FWIW. I acquired a used compressor years ago, rang the manufacturers to try and date it and asked about testing etc. Their technical chap said if it was going to fail it would split rather than explode. That's reassuring enough for me.

Another: I SCUBA dive, Another diver was idly picking at the rust on the bottom of a 3l 200bar pony cylinder. A decent flake fell off and it started hissing from the small hole he'd created. Eeek.

 

[brightspark]

A FWIW. I acquired a used compressor years ago, rang the manufacturers to try and date it and asked about testing etc. Their technical chap said if it was going to fail it would split rather than explode. That's reassuring enough for me.

Another: I SCUBA dive, Another diver was idly picking at the rust on the bottom of a 3l 200bar pony cylinder. A decent flake fell off and it started hissing from the small hole he'd created. Eeek.

I though diving bottles HAD to be tested that's not much cop if not and your 50 foot down in the briny and it gives way

 

[cheb]

They do, I can't remember the regularity. Them being checked when filling depends on the filler.