Helium party cylinder – air tank?

[BazyleParticipant @bazyle]

After a childrens’ party in the church hall an empty helium cylinder was left behind. About 20 litres comparing to my standard small compressor. Oddly it has no pressure information on it at all but best google ai bot finds is at least 18 bar for these disposable ones. So is it suitable as a sprayer reservoir? Drawback is lack of  condensate drain. Seems a particularly bad example of single use disposable stuff.

[Michael GilliganParticipant @michaelgilligan61133]

For information only … I take NO liability:

https://www.instructables.com/Reusing-a-Disposable-Helium-Tank/

MichaelG.

.

They are very thin … but you’re a grown-up.

[old martParticipant @oldmart]

If you want to drill it for a drain, the round end opposite the valve would have the thickest metal, then use it in the upright position.

It reminds me of back when I was working with aircraft instruments and oxygen equipment. The boss got a cylinder of hydrogen for the village fete to fill balloons with, a big one about 4 foot 6 inches feet high and 10 inches diameter and about 3000psi from BOC where we got our oxygen. He put a gauge on it and regulator and turned it on and the gauge exploded. Nobody was hurt, and everyonerealised the mistake. The gauge was an oxygen one andthe bourdon tube had remaining oxygen at standard air pressure in it and the hydrogen at 3000psi made an explosive mixture when he turned the valve on.

 

[Bazyle]

On 1 November 2025 at 18:30 Bazyle Said:

…So is it suitable as a sprayer reservoir? Drawback is lack of  condensate drain. Seems a particularly bad example of single use disposable stuff.

Discussed this before.  The bar rating isn’t trustworthy on it’s own, because the life-time also matters.  When a pressure vessel’s only inflated once, the metal can be much thinner because it doesn’t have to cope with metal fatigue.  In contrast. air-compressor reservoirs are flexed repeatedly, and thickened to cope.

How safe it is to repurpose a Helium cylinder depends on how often it’s pressurised, and to what pressure.  As we don’t have access to the design parameters, the limits are guesswork.

But, operated well below 18bar, it will take a lot of cycles to break an 18bar cylinder, so maybe it’s useful.  Bur consider which of these two scenarios is closest to your Use Case:

• Cylinder occasionally operated at much reduced pressure with no-one nearby.  Low risk and low impact, so go for it,
• Cylinder held between thighs and frequently operated at 18bar.  High risk and high impact.  Anyone who values his cojones should stop and think.   Especially if a third-party might be injured, A civil compensation suit could strip you of property and savings.  These days accidents aren’t free! Unlike the good old days, those found responsible for injuries are held accountable.  Victims don’t go uncompensated, and it’s not cheap!

Dave

[EmgeeParticipant @emgee]

I many years ago modified the screw on end of a fire extinguisher to add an inlet, outlet and pressure gauge to use as a resevoir for a fridge compressor when using an air brush, haven’t used it for years but it’s still in my workshop somewhere.
The pressure obtained from the compressor was less than halve the stamped safe working pressure on the fire extinguisher but it worked well with the air brush.

Emgee

 

 

[Nigel Graham 2Participant @nigelgraham2]

Worth considering too if the inside of such a cylinder has more than very light protection against corrosion. They are for filling with dry gas in controlled conditions, not air with uncertain levels of water-vapour.

Indeed you point to this in you comment about a drain-valve.

If you do go ahead, could you fit a combined take-off valve and drain-valve in the top fitting, and use it upside-down? That would save drilling into the cylinder, with the attendant hazard of weakening it.

[Robert Atkinson 2Participant @robertatkinson2]

These cylinders have an anti-refill non-return valve (NRV) as part of the outlet valve. It’s just a ball on a seat. To remove the NRV you need to remove the outlet valve. This is held in by the top of the valve body being swaged around the valve stem. This needs to be carefully ground away.

Personally I would not want to use one of these at more than about 3 bar.

Robert.

[BazyleParticipant @bazyle]

Thanks for the replies. I didn’t know about the anti-fill valve. My little airbrush pump is very low pressure and does work ok anyway so might just go to the recycling. I think if one used an airbrush at 18 bar it would be like a jet engine – one or two is enough.

[duncan webster 1Participant @duncanwebster1]

You can get normally open solenoid valves for not a lot of money. One of these could be arranged to blow down the tank when you switch off/unplug. I often forget to operate the manual one on my set up.

[not done it yetParticipant @notdoneityet]

Use it at your own risk.  Simple enough to test it hydrostatically <u>after</u> modification and then at safety-conscious intervals.  It would need a safety valve as well, of course.

[old mart]

On old mart Said:

It reminds me of back when I was working with aircraft instruments and oxygen equipment. The boss got a cylinder of hydrogen for the village fete to fill balloons with, a big one about 4 foot 6 inches feet high and 10 inches diameter and about 3000psi from BOC where we got our oxygen. He put a gauge on it and regulator and turned it on and the gauge exploded. Nobody was hurt, and everyone realised the mistake. The gauge was an oxygen one and the bourdon tube had remaining oxygen at standard air pressure in it and the hydrogen at 3000psi made an explosive mixture when he turned the valve on.

 

If that story is true then someone would have been (rightly) liable to prosecution or at least to lose their job.  BOC hydrogen cylinders (and all others I’ve ever come across) have LH threads, and all oxygen regulators are RH.  This is deliberately done to stop oxygen heads being used on cylinders of inflammable material.  Making an adaptor to convert RH to LH threads would have been considered a sackable offence in any lab where I worked.

[old martParticipant @oldmart]

An air brush would only need about 3 bar or 45psi to work, a litre plastic fizzy drink bottle would hold that much.

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