Thread: Transporting oxy-acetylene

LPG cylinders can still easily explode when exposed to high heat for several reasons;

If the pressure relief valve is old or faulty

Or if the rate at which the pressure builds up (from either very high heat or rapid rate of rise in temp) then a situation can occur where the relief valve cannot keep up. So that even though the relief valve is operating, the pressure inside is still increasing. A tell tale sign of this happening is if the audible pitch created by the relief valve operating is increasing in sound level and often in pitch or frequency. If you are near that then one of two things needs to happen quick smart; withdraw to a safe location (Enjoy the show) or get water onto it quick smart.

Also, as stated above in an earlier post, even if the relief valve is doing it's job, if the flame impingment is on a part of the cylinder that no longer has liquid lpg behind it to absorb the heat, the wall of the cylinder can still fail.

When it fails, it changes from liquid to gas and in doing so expands approx 271 times. It then mixes with air at between 2.1% and approx. 10% to make an explosive mix.

As you can see, a small amount of LPG makes a large volume by air when it explodes.

Incidently, acetylene is no where near as fussy with its mix ratios to create an explosive mix with air. It has a massive explosive range;

2.5% - 100%

Even in the absence of oxygen it can decompose. Hence why it's stored in a honeycomb with acetone.

Simon

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Originally Posted by Chas

I don't doubt your experience, but I am left wondeing why the cylinders exploded. All LPG cylinders I have encountered have a safety pressure rupture disk incorporated in the valve, as do other gas cylinders I have come across.
Chas.

G/day Chas, I guess it was the intense heat from the bushfire, there was some debate about the temperature that day but I think that the consensus was 46 degrees, a mate that is in the SES reckoned it was over 48 C.
So the bush was dry as burnt toast and coupled with the hot temperature there were wind gusts over 90 kph pushing the fire along.
We had 6 ft long strips of bark and up to 4 foot long sticks blackened by the fire falling from the sky a couple of hours before the bushfire was in sight, people were putting out spot fires all over the town.
The mountain to the south east of me went up and the main fire was approaching from the north west, it got to about 1.5 - 2 ks
from me before the wind changed, the roar from the fire was huge.
In the aftermath there were many cars that had pools of melted aluminum under them from the engines and transmissions and formed little aluminum creeks as the aluminum flowed down hill.

So I guess to answer your question I will ask a question.....What would happen to an LPG bottle if you put it in a blast furnace?

cheers, shed

Originally Posted by simonl

Incidently, acetylene is no where near as fussy with its mix ratios to create an explosive mix with air. It has a massive explosive range;

2.5% - 100%

Even in the absence of oxygen it can decompose. Hence why it's stored in a honeycomb with acetone.

Simon

Adding to the last point, also why acetylene regulators only go to 150kPa. Attempting to supply at higher pressures can also lead to decomposition.

Saw a bloke with a 'franken-regulator' which he'd cobbled together himself from a different gas type to to convert to acetylene service. I think he was ' ' this close to having an accident where he'd need to be mopped up off the workshop floor.

Thanks for the replies. i have to move and don't have a lot of time but one thing which is apparent from the range of replies is the safety risks with this sort of equipment. I reckon I've used the oxy gear probably 3 or 4 times over the last 5 years so it just doesn't seem worthwhile keeping it when I compare the benefits over the risks. Haven't found anyone available to transport it so looks like a slow walk coming up.