Well that was new to me

Sep 26, 2023 Last reply: 2 years ago 7 Replies

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John Rumm 2 years ago

I got a oxy-propane torch the other day so I could more easily heat metal etc. So I tried it out, worked nicely. Then I thought, I could do with a trolley to cart it about and make it easy (and safe) to store, move use etc.

So I found an old garden trolley in the garage and turned it into this:

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I put all the gear on it, and tried it. No gas would flow. Odd. I checked the connections. The bottle knob was open, the regulator knob set to provide pressure. The flashback arrester fitted the right way round. Opened the hose connection at the bottle end and it released gas, but not the one at the torch end. Checked the hose was not kinked...

Eventually I realised that both the hoses have a very discrete non return fitting at one end (it looks almost identical - but has a slightly longer brass section, and the profile on the mating surface is slightly flatter than the more rounded one on the bottle connection).

Needless to say when I carefully laid them out straight on the lawn to get the curl out of them, and cable tied them together, I did not get them running in the same direction.

So I had to cut all the ties and do it again. I have never seen gas hoses like that before, and even the listing that I bought them from made no mention of this feature.

Is this a common feature?

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wasbit 2 years ago

Dunno as I've never used them but I was aware that hoses had flash back arresters. Presumably what you found.

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Tim+ 2 years ago

I don’t think flashback arresters are the same as non-return valves though.

Tim

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John Rumm 2 years ago

I do have flashback arresters, but those are separate, and are fitted between the regulator and the hose.

These are non return valves on the far end of the hoses.

This is the brand of hose:

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Note the "Fitted with check valves conforming with EN730" - needless to say I only found that after I found out the hard way :-)

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SH 2 years ago

there are certain gas combinations you do not want happening due to spontaneous combustion/explosion, I seem to recall H2 and O2 in certain concentrations so the non return valves would stop gas from one bottle getting into the other and the cylinder then becoming a rocket.

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John Rumm 2 years ago

Yup, I can see the advantages of having a non return valve, just wondered how common it was built into the hose like that? (especially since most users will have flashback arresters and they usually have non return in them).

Having one at the torch end will stop one gas being forced back up the other hose if the regulator pressures are very unbalanced, which is probably a good thing. Probably less useful if you melt through a hose with your lit torch though!

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SH 2 years ago

One would expect the hoses to contian flame retardant and non-cmobustible properties and to char rather than melt (i.e. a fluoroelastomer such as PTFE)

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John Rumm 2 years ago

I did manage to char a propane hose some years ago with a roofing blowtorch... the flame did not hit it for that long. It caused it to acquire a blacked bobbly texture on the surface. But it did not melt in a substantial way.

I it might not fare as well against an oxy-propane flame though. Still I have no desire to find out!

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