Gas stoves, windshields and... explosions?

Talk about anything.

Moderators: Bearbonesnorm, Taylor, Chew

Post Reply
Landslide
Posts: 884
Joined: Fri Jun 30, 2017 5:00 pm

Gas stoves, windshields and... explosions?

Post by Landslide » Mon Aug 03, 2020 4:21 pm

So, I have an Alpkit Kraku stove, and one of Stu's magnetic windshields, and I put a little video of it on my Instagram profile.
Someone commented:
With that much gap you're most likely safe. But the thermodynamicist in me cringes at full windscreen around the gas canister.
When I asked for a little more detail, he added:
Gas canisters can overheat from the reflected and contained heat, and then explode.
Your setup should be fine with that much gap in the windscreen, but as a chartered engineer I wouldn't sign off a risk assessment ;-)
These screw-on stoves should be used with a windscreen that only covers the burner head.
Anyone got any further knowledge/expertise/experience on this? Additional info - I'm using a 300ml mug (pretty small), and there's a gap all the way around the mug.

User avatar
Shewie
Posts: 243
Joined: Sat Oct 05, 2019 5:27 pm
Location: Leeds
Contact:

Re: Gas stoves, windshields and... explosions?

Post by Shewie » Mon Aug 03, 2020 4:40 pm

I should think you'll be fine for boiling water up for brews and dehydrated meals etc, I'd be more concerned if using one for a long time cooking "proper" food.

My mate tried one of the little stubby Chinese burners similar to the Kraku and had issues with heat reflecting back and getting the gas can scary hot, but he cooks and simmers for ages at meal times, that was with a free standing windscreen.

User avatar
UnderTheRadars
Posts: 209
Joined: Mon Jun 02, 2014 8:12 pm
Location: Stourbridge/North Col of North Worcestershire Alps

Re: Gas stoves, windshields and... explosions?

Post by UnderTheRadars » Mon Aug 03, 2020 4:41 pm

Never thought about it before, but it makes sense
Image

User avatar
thenorthwind
Posts: 994
Joined: Thu Mar 10, 2016 6:07 pm
Location: Newcastle

Re: Gas stoves, windshields and... explosions?

Post by thenorthwind » Mon Aug 03, 2020 4:48 pm

Somewhat doubt it. The heated air will rise quickly, drawing in plenty cold air through whatever small gap there might be, and the cylinder is cooling from the expansion of the gas (the cylinder getting too cold to maintain pressure is usually the problem).

I don't know what the safety factor is on those canisters is or to what temperature they'd have to be heated for them not to be able to withstand the increased pressure, even when full of gas, but I suspect it's pretty unlikely. Consider also that to "explode", the flow of gas coming out through the stove and being burnt would have to be insufficient to reduce that pressure too (you'd probably notice the stove roaring even more loudly than usual).

I used to fire marshal at music festivals and you'd see the occasional cheap butane cylinder (which probably have a thinner wall than the propane mix canisters) that had been thrown on a fire ( :roll: ). They would eventually explode, but they last a surprisingly long time, though if they were full I guess it would be a lot shorter, not to mention more spectacular.

Sounds like an imagined problem to me.

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Mon Aug 03, 2020 5:23 pm

Especially when melting snow this is indeed a risky thing, since the stove is running for quite a bit.
Also when not melting snow, but boiling large amounts of water with a windshield in warm summer weather, the can gets hot fairly quick, despite the fact that gas cools down when it's expanding (when depleting the canister). I feel it to be okay when the canister is warm but not hot to the touch.
Obviously the canister gets warmest ontop and can get hot even if the canister is far from bulging. So I touch it in different places to test it.

The canisters have a safety design with the concave bottom.
When too much pressure is built up (by heating the canister and contents), the bottom will pop outwards, sending the can, stove and pot skywards. Once after touch down, you'll get a large flame from the stove since liquid gas is running through the jet as the stove and can lie on the ground.

Once happened to me, despite not using a windshield.
Stove was running for a while to melt a total of about 4 L and my mate and I were busy breaking down camp, rather than paying attention to the stove.
What was a sketchy situation (in a very, very remote part of the earth, high up a mountain) thankfully only ended in loss of water and a cracked thumb nail on the last day of our expedition.

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Mon Aug 03, 2020 5:35 pm

Oh and...
I never run stoves fully opened. They're more efficient turned up half way or even less, especially with small diameter pots.

Not going full gas on the stove will also deflect less heat and mitigate the risk to blow it up, unless, of course, you use a fully enclosing windshield, which would be stupid, no matter what.

Only use fully enclosing windshields with remote gas stoves.

I also had a scary moment with an integrated petrol stove, blowing it's safety valve, sending liquid petrol past the jet, igniting it and causing a 2 m high flame.
The Juwel 34 stove had/has quite a reputation and is called Barthel-bomb...
Similar problem...

User avatar
Bearbonesnorm
Posts: 18783
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Gas stoves, windshields and... explosions?

Post by Bearbonesnorm » Mon Aug 03, 2020 5:37 pm

In theory it is possible, however in reality, there's far too much air gap for that to happen. If you use a canister stove with the canister / stove fully enclosed* then the risk increases but it's still small.



*not recommended although many people do and they're not all dead.
#corporate shill for hire

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Mon Aug 03, 2020 7:35 pm

Bearbonesnorm wrote:
Mon Aug 03, 2020 5:37 pm
In theory it is possible, however in reality, there's far too much air gap for that to happen. If you use a canister stove with the canister / stove fully enclosed* then the risk increases but it's still small.



*not recommended although many people do and they're not all dead.
Did it ever happen to you?

As I don't think so; better give it a try in a safe environment. I bet you'd be surprised how little it takes to see it happen, preventing you from stating such assumptions like the above.

People don't want to seem stupid, so they are likely not going to tell the tale of nearly burning themselves by turning the stove into a bomb. That's more likely why you don't hear many such stories.

I stand by my stupidity and have learned my lesson.

User avatar
Bearbonesnorm
Posts: 18783
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Gas stoves, windshields and... explosions?

Post by Bearbonesnorm » Mon Aug 03, 2020 8:01 pm

In theory it is possible, however in reality, there's far too much air gap for that to happen
Gian, the above was referring to the stick on magnetic shields, which don't fully enclose the canister.
If you use a canister stove with the canister / stove fully enclosed* then the risk increases but it's still small.
I didn't say it couldn't or doesn't happen but given the design of gas canisters, the chances of it actually exploding are pretty slim.
People don't want to seem stupid, so they are likely not going to tell the tale of nearly burning themselves by turning the stove into a bomb. That's more likely why you don't hear many such stories.
I'm thinking the internet would be awash with stories and warnings from those having survived. :wink:
#corporate shill for hire

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Mon Aug 03, 2020 9:33 pm

Bearbonesnorm wrote:
Mon Aug 03, 2020 8:01 pm
Gian, the above was referring to the stick on magnetic shields, which don't fully enclose the canister.
You don't need to fully enclose it to get it hot enough to cause the canister to bulge.
I know, getting eg 0.5 L of cold water to a temperature close to boiling with a screw on top stove and full wind screen will most likely not cause any trouble.

But then what if your can was in a black bag on a sunny day in a hot area? And you're tired from riding all day, have fired up the stove and whilst your supper comes closer you fix some gear and forget for just 15 min what the stove is doing... suddenly it becomes an issue.
The canister I blew was standing on an avalanche shovel in snow at an air temperature of well below freezing. I'm also guessing but have done dialectic in this case :wink:
Bearbonesnorm wrote:
Mon Aug 03, 2020 8:01 pm
I didn't say it couldn't or doesn't happen but given the design of gas canisters, the chances of it actually exploding are pretty slim.
Yes, an explosion is unlikely. First it'll bulge the bottom. Depending on where your stove is - mostly close by - there's quite the potential for a story as the liquid gas flame is pretty impressive. I've not seen the height it jumps, but given the force it takes, that too must be impressive. I think we can agree that for drama it doesn't need to explode.
Bearbonesnorm wrote:
Mon Aug 03, 2020 8:01 pm
warnings from those having survived
I think just a small percentage of the stupid ones are 1. unlucky to get the change to see it happen, 2. lucky enough to survive it and 3. eager to admit their stupidity.
And 4. land on this forum or others, where you finally come across.

I simply do not recommend using a wind screen that covers the stove and canister. Just as the cited statement in the opening post.
I much appreciate this discussion since Landslide surely has a better clue of the potential risks, can make his own decision and will keep an eye on the stove, be it with or without a wind screen.

P.s.: does any one have a photo of the discussed wind screen? Had a quick look through the BB shop but couldn't figure which one was meant.

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Mon Aug 03, 2020 9:39 pm

Here, from a quick google.

https://backpackinglight.com/canister_s ... S8qPBOUegJ

Scroll down to find some clues about how to (not) use a wind screen.

Landslide
Posts: 884
Joined: Fri Jun 30, 2017 5:00 pm

Re: Gas stoves, windshields and... explosions?

Post by Landslide » Mon Aug 03, 2020 10:05 pm

Alpinum wrote:
Mon Aug 03, 2020 9:33 pm
P.s.: does any one have a photo of the discussed wind screen? Had a quick look through the BB shop but couldn't figure which one was meant.
Here's mine in action.
https://www.instagram.com/p/CDMRwc8FbhO/

Thanks for all the comments. As I'm only using it to boil small quantities of water, I'm not hitting the panic button. I'll make sure not to forget about it though.

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Tue Aug 04, 2020 6:14 am

Landslide wrote:
Mon Aug 03, 2020 10:05 pm
Alpinum wrote:
Mon Aug 03, 2020 9:33 pm
P.s.: does any one have a photo of the discussed wind screen? Had a quick look through the BB shop but couldn't figure which one was meant.
Here's mine in action.
https://www.instagram.com/p/CDMRwc8FbhO/

Thanks for all the comments. As I'm only using it to boil small quantities of water, I'm not hitting the panic button. I'll make sure not to forget about it though.
Since the screen seems to touch the can... good luck with the Darwin award :wink:

Landslide
Posts: 884
Joined: Fri Jun 30, 2017 5:00 pm

Re: Gas stoves, windshields and... explosions?

Post by Landslide » Tue Aug 04, 2020 7:36 am

Given I've already passed my genes on to the next generation, I don't qualify. ;)

User avatar
thenorthwind
Posts: 994
Joined: Thu Mar 10, 2016 6:07 pm
Location: Newcastle

Re: Gas stoves, windshields and... explosions?

Post by thenorthwind » Tue Aug 04, 2020 8:10 am

Alpinum wrote:
Tue Aug 04, 2020 6:14 am
Since the screen seems to touch the can... good luck with the Darwin award :wink:
But there's a gap of at least 90 degrees at the front?

It seems my previous comments were probably overly dismissive of the problem. I hadn't considered the more extreme situations like melting snow for long periods, because they're outside my experience. I don't even have a windshield and doubt it would be a problem for my usage, but if I ever use my stove in different circumstances in the future, I've learnt a lesson here to at least consider the reflected heat.

User avatar
Bearbonesnorm
Posts: 18783
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Gas stoves, windshields and... explosions?

Post by Bearbonesnorm » Tue Aug 04, 2020 9:25 am

Since the screen seems to touch the can... good luck with the Darwin award
You'll be happy to know Gian, that after 12 minutes running the bottom third of the shield is still cool to touch - Ti really doesn't transfer heat well. :wink: In the interests of science, I sat for the same 12 minutes with my finger sitting on top of the canister at the rear of the shield. Yes, there is (quite obviously) some heat present but it wasn't uncomfortable and I still have all my skin and it's the correct colour. I'd need to borrow a decent thermometer* to check but it would appear that the overall temp of the cansister is actually lower after those 12 minutes than it was before ... that'll be the liquid inside vapourising into gas then.

*this is something I will do.
#corporate shill for hire

User avatar
ScotRoutes
Posts: 6082
Joined: Mon Mar 18, 2013 9:56 am
Location: Cairngorms
Contact:

Re: Gas stoves, windshields and... explosions?

Post by ScotRoutes » Tue Aug 04, 2020 9:30 am

the overall temp of the cansister is actually lower after those 12 minutes than it was before ...
That's my expectation based on experience.

User avatar
Alpinum
Posts: 1746
Joined: Thu Mar 06, 2014 5:38 pm

Re: Gas stoves, windshields and... explosions?

Post by Alpinum » Tue Aug 04, 2020 10:20 pm

Bearbonesnorm wrote:
Tue Aug 04, 2020 9:25 am
Since the screen seems to touch the can... good luck with the Darwin award
You'll be happy to know Gian, that after 12 minutes running the bottom third of the shield is still cool to touch - Ti really doesn't transfer heat well. :wink: In the interests of science, I sat for the same 12 minutes with my finger sitting on top of the canister at the rear of the shield. Yes, there is (quite obviously) some heat present but it wasn't uncomfortable and I still have all my skin and it's the correct colour. I'd need to borrow a decent thermometer* to check but it would appear that the overall temp of the cansister is actually lower after those 12 minutes than it was before ... that'll be the liquid inside vapourising into gas then.

*this is something I will do.
:-bd
Thanks for checking.

I (too) wouldn't have thought to ever blow a canister and regularly experience how much effect running time and intesity, wind, ambient temperature, material choices etc. have, yet in the prior mentioned circumstances it still happened. I still use wind screens on stoves similar to the Kraku, but am much more careful since and thus don't recommend a close fitting screen that sits around the stove and the can.
thenorthwind wrote:
Tue Aug 04, 2020 8:10 am
but if I ever use my stove in different circumstances in the future, I've learnt a lesson here to at least consider the reflected heat.
I guess that's all we wanted to achieve in this discussion.
Mostly it'll be just fine and sometimes we need to keep a close eye/finger on it.
:-bd
Landslide wrote:
Tue Aug 04, 2020 7:36 am
Given I've already passed my genes on to the next generation, I don't qualify. ;)
Thanks, that's a few tons CO2 less in the environment. *dirty laugh*

fatbikerbill
Posts: 208
Joined: Wed Dec 30, 2015 6:25 pm
Location: manchester

Re: Gas stoves, windshields and... explosions?

Post by fatbikerbill » Thu Aug 06, 2020 10:27 pm

Perhaps just no one has survived to say 'yeah that must be what happened'.

I use a kraku with no issues (so far).

I have read that the remote stove style is a lot more efficient, but perhaps that is more due to be being lower, so less prone to wind. Throw in a wind shield then even better.

User avatar
htrider
Posts: 3116
Joined: Wed Apr 02, 2014 10:51 pm
Location: Fife
Contact:

Re: Gas stoves, windshields and... explosions?

Post by htrider » Fri Aug 07, 2020 4:33 pm

Just read this after running my gas stove with BB shield (tm) for several minutes on several occasions during my perambulations this week. Never even occurred to check it was a problem but apparently it isn't.....

Post Reply