How can a steel thermos drinks flask fail?

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Simon Robinson 4 on 09/11/2020 20:19:37:

Posted by Nicholas Farr on 09/11/2020 19:08:05:

Hi, the price really does reflect how long they will keep the contents hot. My 1 litre one that I used when out on site work would stay to hot to drink all day if it wasn't opened, but would still be hot enough for making a mug of coffee at the end of the day after using it at dinner time. I only ever put boiling hot water in it and make tea or coffee when needed. I think it cost me about £35.00 four or so years ago and it still works fine, not that I do site work anymore, but it's handy when out and about, especially at the present time where you don't have to mix with too many other people.

Regards Nick.

Edited By Nicholas Farr on 09/11/2020 19:10:56

Is it a steel or glass flask?

Hi Simon, it is stainless steel, glass ones don't often last long in working enviroments as they rattle about in the van or get knocked over.

Regards Nick.

[Colin HeseltineParticipant @colinheseltine48622]

I've was given as a present by my daughter one of the Stanley Master (Black) stainless steel flasks and this claims to keep contents hot for 24hrs. Certainly if not opened it is hot 24 hrs later.  Certainly I would expect it to perform at around £70.

I can make a hot drink at 6am one day and have a hot drink for breakfast next day when camping and away for a weekend.

Cant fault it.

Colin

Edited By Colin Heseltine on 09/11/2020 22:18:50

[not done it yetParticipant @notdoneityet]

Easy – the vacuum leaked out

That’s funny – I’ve never ever come across a ‘leaking vacuum’. Where did it leak to?🙂

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 09/11/2020 22:51:56:

Easy – the vacuum leaked out

That’s funny – […]

.

I presume it was intended to be

MichaelG.

[Andy_GParticipant @andy_g]

Posted by not done it yet on 09/11/2020 22:51:56:

Easy – the vacuum leaked out

Where did it leak to?🙂

It'll be under the stairs, with the other one

[larry phelan 1Participant @larryphelan1]

They are

A CRAP

B JUNK

C Not worth a S——-T

Apart from that, they,re OK !

[not done it yetParticipant @notdoneityet]

The simple point was that a vacuum never leaks away. There is nothing, by definition to leak to anywhere.

The only thing that can happen is for a fluid to leak into the space – generally, but not always, an air leak but most certainly not a vacuum leak. Lots think that vacuums leak but the simple truth is that those people don’t understand basic Physics.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 10/11/2020 14:45:24:

The simple point was that a vacuum never leaks away. There is nothing, by definition to leak to anywhere.

The only thing that can happen is for a fluid to leak into the space – generally, but not always, an air leak but most certainly not a vacuum leak. Lots think that vacuums leak but the simple truth is that those people don’t understand basic Physics.

.

Surely the whole point is that Andy was joking

… The devilish smiley thing was a pretty good hint.

MichaelG.

[MeunierParticipant @meunier]

Posted by not done it yet on 09/11/2020 22:51:56:

Easy – the vacuum leaked out

That’s funny – I’ve never ever come across a ‘leaking vacuum’. Where did it leak to?🙂

No pressure to find an answer then…………..
DaveD

[Stephen FollowsParticipant @stephenfollows82099]

I have two 1 litre Thermos flasks, that is Thermos make not cheap ones. Before filling with desired drink I pour boiling water in to heat them up. put top on and leave for a few minutes. Pour out and add drink, that way the drink is not heating the inside of the flask.

[Dr. MC BlackParticipant @dr-mcblack73214]

Pre-heating flask with boiling water before filling with same kept my contents of my flasks hot for longer than a day out. Unfortunately, they were condemned by insurance company after the fire and I’ve not been able to replace with same design.

I think that a larger volume of hot liquid in large flask, eg one litre, will remain hot for longer than water in half litre flask.

MCB

[not done it yetParticipant @notdoneityet]

Posted by MC Black on 16/11/2020 23:52:20:

Pre-heating flask with boiling water before filling with same kept my contents of my flasks hot for longer than a day out. Unfortunately, they were condemned by insurance company after the fire and I’ve not been able to replace with same design.

I think that a larger volume of hot liquid in large flask, eg one litre, will remain hot for longer than water in half litre flask.

MCB

Surface area of a sphere is related to the square of the radius, while the volume is related to the cube of the radius. Simply put, that means the volume increases more than the surface area as the size increases.

That means a larger volume loses energy from a relatively smaller volume, resulting in less heat loss.

Regarding the comparison of ‘hot liquid’ to water may be misleading – there is likely greater heat content in some liquids (perhaps talking soups or other food-stuffs) than in the same volume of water. All to do with the particular specific heat of the liquid and heat losses at the same rate (at any particular temperature delta). A concentrated sugar solution would, of course, weigh far more than the same mass of water for instance.

We need ‘fair comparisons’ before making sweeping statements without qualification.

[Anthony KendallParticipant @anthonykendall53479]

Posted by Andy Gray 3 on 10/11/2020 11:00:03:

Posted by not done it yet on 09/11/2020 22:51:56:

Easy – the vacuum leaked out

Where did it leak to?🙂

It'll be under the stairs, with the other one

I think that's a sweeping generalisation

[SillyOldDufferModerator @sillyoldduffer]

Posted by Anthony Kendall on 17/11/2020 09:15:10:

Posted by Andy Gray 3 on 10/11/2020 11:00:03:

Posted by not done it yet on 09/11/2020 22:51:56:

Easy – the vacuum leaked out

Where did it leak to?🙂

It'll be under the stairs, with the other one

I think that's a sweeping generalisation

This exchange of humour brought back fond memories of my late father, a qualified Electrical Engineer with a successful and wide-ranging career. Clever chap, but he absolutely didn't get puns or satire!

Watching TV with dad I noticed he missed at least half the jokes. To him The Simpson's was just a kiddy cartoon, whereas I enjoyed the many grown up references to American and International Politics, the Hollywood machine, Media outlets, Celebrities, Gun Culture, Crime and much else. And I knew that some of it was over my head too; plenty of American celebrities and goings on don't make it over the Atlantic.

Likewise, I knew "Round the Horn" was rude, but listening to repeats carefully today, I find it's extremely rude, packed with naughty word-play I didn't understand in my youth!

Intelligence is very diverse. No one is good at everything and in my experience even the most unpromising types turn out to have spectacular skills. And I've met a few near geniuses who were incapable of ordinary life, for example a visiting senior scientist baffled by how to get a meal in a works canteen.

Dave

[Grindstone CowboyParticipant @grindstonecowboy]

I just want to know where I can get some of that talking soup

( JOKE! )

[Dr. MC BlackParticipant @dr-mcblack73214]

Posted by not done it yet on 17/11/2020 07:02:50:

Posted by MC Black on 16/11/2020 23:52:20:

Pre-heating flask with boiling water before filling with same kept my contents of my flasks hot for longer than a day out. Unfortunately, they were condemned by insurance company after the fire and I’ve not been able to replace with same design.

I think that a larger volume of hot liquid in large flask, eg one litre, will remain hot for longer than water in half litre flask.

MCB

Surface area of a sphere is related to the square of the radius, while the volume is related to the cube of the radius. Simply put, that means the volume increases more than the surface area as the size increases.

That means a larger volume loses energy from a relatively smaller volume, resulting in less heat loss.

Regarding the comparison of ‘hot liquid’ to water may be misleading – there is likely greater heat content in some liquids (perhaps talking soups or other food-stuffs) than in the same volume of water. All to do with the particular specific heat of the liquid and heat losses at the same rate (at any particular temperature delta). A concentrated sugar solution would, of course, weigh far more than the same mass of water for instance.

We need ‘fair comparisons’ before making sweeping statements without qualification.

I don't disagree with anything you have written

I only ever put boiling water in flasks so I can make the tea when I want to drink it. Making the tea in the flask would create problems cleaning it and the tea would be too strong (My late Mother would say that it would be "like beer" – sadly it was nothing like beer. I tried!

Incidentally, Denture Cleaner is excellent for removing tea stains from Stainless Steel teapots…… If anybody is interested.

MC

[Peter G. ShawParticipant @peterg-shaw75338]

I thought that pre-heating flasks, of any description, was standard practice. I've been doing it even with glass vacuum flasks or as long as I can remember.

And as far as cleaning is concerned, for glass flasks I have always used sodium bi-carbonate (I think!), or is it baking soda. Anyway, the fizzing and the brown muck that comes off a glass flask makes one wonder what coffee does to ones insides. I don't know about metal flasks, We stopped using flasks for hot ready made drinks in favour of hot water and the makings separate. I would, though, if I had to do it on a badly stained steel flask try detergent powder, and if possible boil the whole thing – it seems to work on metal teapots and the like.

Peter G. Shaw

Edited By Peter G. Shaw on 17/11/2020 10:46:31

[Neil WyattModerator @neilwyatt]

Posted by Michael Gilligan on 09/11/2020 15:58:38:

Posted by Neil Wyatt on 09/11/2020 15:21:53:

I think the answer is that cheap ones have no vacuum and better ones do.

Hence very different performance.

Neil

.

So … What do you think the failure-mode was ?

[ ref. the opening post ]

MichaelG.

It wasn't what I was addressing in my comment, but presumably Micro crack in the weld leading to loss of vacuum.

If it happened in the dishwasher then water may have entered the space making things even worse.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 17/11/2020 11:41:01:

Posted by Michael Gilligan on 09/11/2020 15:58:38:

So … What do you think the failure-mode was ?

[ ref. the opening post ]

MichaelG.

It wasn't what I was addressing in my comment, but presumably Micro crack in the weld leading to loss of vacuum.

If it happened in the dishwasher then water may have entered the space making things even worse.

.

Thanks for the clarification, Neil

We are on the same page

One thing that no-one seems to have mentioned yet is that the internal vessel is usually only fixed to the outer shell at the neck … therefore if laid on its side when full, there can be significant cantilever loads on that welded joint.

MichaelG.

[Author]

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