Cutting Gas Cylinders Open Safely - HELP

[Lewis_RX8]

Yep know all about that. Just in the middle of organising a prosecution for something similar that happened

crikey, My only experience with cutting pressure vessels would be a fire extinguisher that I used as a foundry crucible but don't think there's much chance of that exploding.

 

[Parm]

crikey, My only experience with cutting pressure vessels would be a fire extinguisher that I used as a foundry crucible but don't think there's much chance of that exploding.

Man died in a pretty gruesome way

 

[brightspark]

like I said, last time I turned one upside down to empty it, it left a substantial mound of frozen propane slush.

Obviously too dangerous to leave lying around so I lobbed a match on it.

wish I had videoed it, won’t be doing that again in a hurry.

didn't it evaporate or was it a cold day

 

[Lewis_RX8]

Man died in a pretty gruesome way

Suppose there cant be much a pair of FR overalls or any similar PPE can do in that situation once its exploded. Sounds awful

 

[Screwdriver]

didn't it evaporate or was it a cold day

wouldn’t have been in the summer so probably a cold day. It managed to persist for a surprisingly long time.

 

[Memmeddu]

That is a damned fine idea. I had considered a gas purge with argon but I don’t value my life that highly. Gas is expensive. Air is not.

Those are epic words

My take on this topic is that cutting up gas cylinders is dangerous so while there is no “safe” way to do it, compressed air is now on my list of things to try next time I need to chop one up.

I know that people who repair fuel tanks use a water steam purge prior welding them.
We use another system but it's not advertisable

I'd like to try Steam prior to do air purge also because you are leaning the stechiometric values , making the propane air mixture more prone to detonation
Which is not good IMHO

 

[slim_boy_fat]

I have had a 47 k bottle as a "buffer tank" on the plasma table .
If i put a blow gun on to it still strings of propane smelly stuff
It must have had tens of thousands of litres of air through it
It was washed with water as well

Sticks around for ages, even when filled/emptied/refilled/ etc since I made this for topping up tyre pressures [compressor is too far from the car to use], still stinks when used as a 'blower-away' in the shed

 

[8ob]

Same as most, fill with water and leave a few days, the smell is added to the gas and not a problem.

 

[Melvyn Best]

Seeing the thread title reminds me of a visit to our local welding suppliers where they had the remains of an acetalyn cylinder recovered from a garage workshop fire, glad I wasn’t near it when that went up.

 

[The_Yellow_Ardvark]

Seeing the thread title reminds me of a visit to our local welding suppliers where they had the remains of an acetalyn cylinder recovered from a garage workshop fire, glad I wasn’t near it when that went up.

That is the remains of 2 X 2kg CO2 extinguishers, after being in a small workshop fire.
Bottom one went off like a missile. Smashing the head cap into the wall.

Top one, exploded.

There is a safety valve on all BS, Kite marked and EU approved units.
Theses had them, but they had failed. Looking at the one what was in the compressor shed. They were cheep copies or cheep recondition ones.

 

[Maker]

Seeing the thread title reminds me of a visit to our local welding suppliers where they had the remains of an acetalyn cylinder recovered from a garage workshop fire, glad I wasn’t near it when that went up.

Somewhere I've got the twisted remains of boules ball that went pop on a fire, turns out they're just a steel shell, presumably full of wet sand or something. "Pop" is an understatement!

 

[Welderpaul]

Same as most, fill with water and leave a few days, the smell is added to the gas and not a problem.

What have you made there @8ob ?

 

[Screwdriver]

didn't it evaporate or was it a cold day

Well I had a quick Google this morning and the mechanism is quite interesting. Propane "slush" doesn't melt into a liquid, it sublimes directly into a gas. The "ice" or frozen propane is referred to as a propane hydrate and the presence of water has a number of consequences regarding its behaviour. I skimmed this: https://***********/ycwrjf6h and if anyone wants to read it, let me know what it says!

We all know propane or LPG (or even petrol) can form a slushy "ice" as the pressure is released, it seems it can do that at around 5 degrees C. When you think about it, as the gas bottle is emptied, it will chill the bottle enough to make it "frosty" on the outside. You then have a very good refrigerator to keep small quantities of propane hydrate sticking to the insides - after flushing with water...


<edt> TinyURL has failed, here's the link:

https://books.google.co.uk/books?id...Q#v=onepage&q=propane ice sublimation&f=false

 

[Pete.]

What have you made there @8ob ?

I reckon that's a hydraulic oil pump.

 

[slim_boy_fat]

I reckon that's a hydraulic oil pump.

Possibly for use as a transfer pump if needed on site?

 

[8ob]

Twas this https://www.mig-welding.co.uk/forum/threads/oil-dispenser.75382/

bob

 

[Kayos]

Well I had a quick Google this morning and the mechanism is quite interesting. Propane "slush" doesn't melt into a liquid, it sublimes directly into a gas. The "ice" or frozen propane is referred to as a propane hydrate and the presence of water has a number of consequences regarding its behaviour. I skimmed this: https://***********/ycwrjf6h and if anyone wants to read it, let me know what it says!

We all know propane or LPG (or even petrol) can form a slushy "ice" as the pressure is released, it seems it can do that at around 5 degrees C. When you think about it, as the gas bottle is emptied, it will chill the bottle enough to make it "frosty" on the outside. You then have a very good refrigerator to keep small quantities of propane hydrate sticking to the insides - after flushing with water...


<edt> TinyURL has failed, here's the link:

https://books.google.co.uk/books?id=J_AkNu-Y1wQC&pg=PA45&lpg=PA45&dq=propane+ice+sublimation&source=bl&ots=j2GybJFShv&sig=ACfU3U38Ie3Wdsz72FnBfe5X3eykcT-h4Q&hl=en&sa=X&ved=2ahUKEwjludCR9rfpAhVpAGMBHbaPDXQQ6AEwAHoECBgQAQ#v=onepage&q=propane ice sublimation&f=false

I'm sorry, if you cut a bottle open and found "slush" inside it you were either working somewhere around -180 degrees or had taken a big sniff of the propane first

Sublimation and the freezing on the outside are 2 very different things, the freezing is simply caused by the state change from liquid to gas needing energy. Much how air con works

The clue is in the name Liquid petroleum gas, compressing the gas causes it to liquid, releasing the pressure causes it to boil. At no point is it frozen

I've worked on tanker sized installs with 15kg per hour take off rates, the pipes freeze quite a lot but you dont get slush issues

 

[slim_boy_fat]

Twas this https://www.mig-welding.co.uk/forum/threads/oil-dispenser.75382/

bob

I see I even like the project back then - my memory must be going.....

 

[Screwdriver]

I'm sorry, if you cut a bottle open and found "slush" inside it you were either working somewhere around -180 degrees or had taken a big sniff of the propane first

Sublimation and the freezing on the outside are 2 very different things, the freezing is simply caused by the state change from liquid to gas needing energy. Much how air con works

The clue is in the name Liquid petroleum gas, compressing the gas causes it to liquid, releasing the pressure causes it to boil. At no point is it frozen

I've worked on tanker sized installs with 15kg per hour take off rates, the pipes freeze quite a lot but you dont get slush issues

I didn't find any inside the tank I was cutting open. I made a pile of it on the floor when I inverted the tank to empty it.

It looked for all the world like one of those "Hollywood" explosions when for safety reasons, I lobbed a match on it.

I am referring exactly to the effect you describe; releasing the pressure in a compressed gas causes a temperature drop, I then go on to suggest that effect might allow tiny traces of frozen propane to persist inside the (frozen) tank. As @Memmeddu suggests above, it doesn't take much gas in an enclosed volume to produce a bomb.

 

[Kayos]

I didn't find any inside the tank I was cutting open. I made a pile of it on the floor when I inverted the tank to empty it.

It looked for all the world like one of those "Hollywood" explosions when for safety reasons, I lobbed a match on it.

I am referring exactly to the effect you describe; releasing the pressure in a compressed gas causes a temperature drop, I then go on to suggest that effect might allow tiny traces of frozen propane to persist inside the (frozen) tank. As @Memmeddu suggests above, it doesn't take much gas in an enclosed volume to produce a bomb.

And I'm saying there is no way you tipped frozen propane out of any bottle, ever

The propane does not freeze, the ice on the outside is moisture in the air freezing due to the bottle getting cold

You are correct, it doesn't take much to explode in an ENCLOSED space, the flamabilty limits being 2 to 12% I think, would need to check.

If you did light some frozen slush (maybe in a lab at -180 degrees) it would flare up and burn, not explode and there needs to be confinement for an explosion