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How many of us have a bomb in the kitchen?

Scientific discovery and discussion
UncleEbenezer
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Re: How many of us have a bomb in the kitchen?

#61816

Postby UncleEbenezer » June 22nd, 2017, 8:39 am

I have something altogether more exciting than that in my kitchen. A gas hob.

But the real bomb is just outside the kitchen. A gas boiler.

Plus of course, a range of electronic devices, including those with batteries whose risk of blowing appears empirically higher than any correctly-used kitchen appliance.

Urbandreamer
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Re: How many of us have a bomb in the kitchen?

#61829

Postby Urbandreamer » June 22nd, 2017, 9:19 am

FredBloggs wrote:So, that makes it sensible to replace a very safe and pretty benign refrigerant, R134a, with an explosive one then? To save a few watts on your power bill. Have a look on the web. You may be surprised at how many R600a fridges have caused fires. R134a simply can't do that.


There are compromises everywhere Fred.

Apparently a number of RV fridges still use ammonia, described as "Ammonia is inherently safe and very efficient;" here:
https://www.arprv.com/ammonia-refrigeration.php

The gasses you talk mostly replaced ammonia as, while it is environmentally benign, it has lead to a number of deaths.
The replacement gasses were CFC's, and you know the issue with them. Then came HCFC's which could be used in the same devices and were somewhat better, but no means benign.

You recommend a google, so here is a link to the Wiki page on refrigerant gasses (which provides a nice potted history).
https://en.wikipedia.org/wiki/Refrigerant

Of course we could use Peltier effect devices instead. However we would have to build a lot more power stations, which might also effect the environment.....

I suspect that my fridge/freezer may use R600a and it's replacement almost certainly will. Personally I'm quite comfortable with that.

bungeejumper
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Re: How many of us have a bomb in the kitchen?

#61853

Postby bungeejumper » June 22nd, 2017, 10:53 am

FredBloggs wrote:Thanks. such is the price of progress. R134a was developed by ICI and DuPont as a result of the Montreal protocol in the 1980's and is the main gas used in car air con units. Which kind of puzzles me a little why it has been dropped from use in the domestic market.


If it needed topping up as often as car aircon gas, I could certainly understand why they don't use it in household appliances. ;)

IIRC (and I am as far away from a physicist as you can get), one of the probs with car aircon gas is that the molecules are very small, which means that they can slip through any porous material they encounter. Slowly but inexorably. Might this be a contributing factor?

BJ

midnightcatprowl
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Re: How many of us have a bomb in the kitchen?

#61854

Postby midnightcatprowl » June 22nd, 2017, 10:54 am

We'll wait to see what the outcome of the tower block investigation is. But the early signs are that without an R600a fridge catching fire, the tragedy would never have happened.


Well sort of. The tragedy would not have happened on that day (night) but it appears to have been a fire waiting to happen. Apart from the issue of the insulation panels the single stairway, lack of sprinkler system and various other factors appear to have added up to a time bomb - it wasn't just a fridge bomb.

Where you have large numbers of people in high rise accommodation you have to assume that from time to time fires WILL start. These things actually do happen and can be triggered by the carelessness of individuals, or lack of understanding by individuals of the potential risk of some things, or because of arson or explosion (deliberate or accidental) because of defective wiring in the building as a whole or because of defective appliances. It WILL happen and the building has to be set up so that such fires can be quickly and effectively tackled.

One of my ex-employees was driving home from visiting her husband in hospital when a fire engine passed her going at speed. She was horrified when she got home to find the fire engine parked in front of her own home and fire fighters in her house. Her washing machine (newish machine) had caught fire. In a semi-detached set up all the fire fighters had to do was throw the machine out into the garden and then put it out without risk or damage to the house but you can't do that in a high rise.

Yesterday my local fire brigade was warning people of the risks of leaving mirrors and other reflective objects on sunny windowsills and showing the results of a fire they'd just tackled in a bedroom where the bedding had been ignited via the heat of the sun reflected from a perfectly ordinary mirror standing on a windowsill. I wonder how many people will have gone to work today after quite innocently putting down their bedroom hand mirror on the windowsill?

Fire does happen, it will happen, it is going to happen, but in a tower block it should be possible to contain and fight and extinguish it without the whole block becoming involved.

didds
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Re: How many of us have a bomb in the kitchen?

#61859

Postby didds » June 22nd, 2017, 11:01 am

Warning : possible derail.

So we are aware that there have been terrible terrorist attacks of late, globally, using cars and vans and knives, or bombs.

But given all this and what we seem to have gleaned from Grenfell why don;t terrorist suicide bombers just walk into a tower block and set themselves off? Or come to that leave a bomb in a suitable place and detonate from a safe distance?

didds

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Re: How many of us have a bomb in the kitchen?

#61877

Postby bungeejumper » June 22nd, 2017, 11:24 am

FredBloggs wrote:Car air con systems lose their gas because they HAVE to use flexible hoses, many separable joints and the compressor has a shaft seal along with frequent and very big temperature cycles. Domestic fridges are 100% hermetically sealed units. Do you know anyone who ever had a domestic fridge re-gassed?

No, and that's partly my point. :) Although, as you say, domestic systems don't need the flexible connectors that car systems require, it still might be that the car gas has not proved suitable for technical reasons. I'm sure I could find out that out in minutes, but alas, I suspect that I wouldn't understand the answer even if I knew how to phrase the question. :lol:

BJ

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Re: How many of us have a bomb in the kitchen?

#61890

Postby Urbandreamer » June 22nd, 2017, 11:57 am

FredBloggs wrote:Let me assure you, there are no (serious) technical reasons not to use R134a in domestic appliances. The alternative, R600a is a more efficient refrigerant gas. But there are no free lunches. The price for saving a few watts energy per year is one of greatly increased fire risk IMO. To illustrate the energy use, the new FF I am about to order has running costs of GBP 26.90 per year. Even if R134a was 10% less efficient (it isn't) it would increase your energy bill by precisely GBP 2.69p per year. What price for progress eh?


I certainly didn't initially realise that you were talking about the tower block fire.

How much research have you done? I note that studies were talking about flammable insulation and fittings used in fridges rather than the gas used. Indeed the gas isn't even mentioned in this article.
http://www.coolingpost.com/uk-news/stud ... e-hazards/

As has been said, fires WILL start. What is needed is designs that contain and extinguish them.

I suspect that there are a host of factors in this case that lead to a big tragedy.

We don't know at this point if the ignition point was a fridge or even if the suggested fridge used R600a. I believe that everyone would agree that designs should prevent a fire in one apartment causing the tragedy that happened.

Dod1010
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Re: How many of us have a bomb in the kitchen?

#61897

Postby Dod1010 » June 22nd, 2017, 12:17 pm

midnightcatprowl wrote:
Fire does happen, it will happen, it is going to happen, but in a tower block it should be possible to contain and fight and extinguish it without the whole block becoming involved.


Quite, and the way those tower blocks were originally designed it was a fair assumption that a fire would be contained within any particular flat so that the fire could be extinguished 'without the whole block becoming involved'. Before plastic windows and before the idea of cladding the exterior in another sort of plastic apparently, each flat was designed to be in effect a concrete box. With a one hour or whatever the fire rating is/was for the main door of the flat, the fire could be contained in the flat of origin and extinguished from the rising main in the stair well.

Hence the advice for tenants to remain in their flat whilst the fire services attended to the fire, otherwise the risk is of smoke inhalation, blocking the staircase so as to impede the fire services and so on. What is known as the fire loading is quite small in a flat and there should be no need for sprinklers, which were designed for warehouses and department stores and the like, with large areas with no fire break and high fire loadings.

None of us really knows much about the disastrous fire other than what we have heard/read about in the media but it looks as if the cladding was the main culprit because had it been simply a concrete external wall, flames might have got out of the plastic window but would then have had to leap ten feet or so to the next window up the building. Quite possible but it would have taken some time to have engulfed the whole building.

What seems to have happened is that no-one really thought through the potential consequences of a fire in the new circumstances, and worse, it would seem that the external cladding was not fireproof.

Dod

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Re: How many of us have a bomb in the kitchen?

#62183

Postby didds » June 23rd, 2017, 10:59 am

Even if R134a was 10% less efficient (it isn't) it would increase your energy bill by precisely GBP 2.69p per year. What price for progress eh?


I would suspect the point being made is not the financial savings an individual would make, but the collective power savings the nation wold make.


That doesn't mean FB's individual point is not in itself valid.

didds

chas49
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Re: How many of us have a bomb in the kitchen?

#62234

Postby chas49 » June 23rd, 2017, 12:55 pm

Moderator Message:
This is off-topic for Comfort Cafe. Moved to Science as most of the discussion is about the technicalities. Would further posts please note the new location please (chas49)

supremetwo
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Re: How many of us have a bomb in the kitchen?

#62236

Postby supremetwo » June 23rd, 2017, 12:58 pm

See Hotpoint has drawn the short straw:-

http://www.bbc.co.uk/news/uk-40380584

Anyone who has a white Hotpoint fridge freezer model number FF175BP or graphite fridge freezer model number FF175BG should register their appliance with the manufacturer to receive any updates.
Generally, the model number is found on a bar code on a sticker behind the salad container in the fridge.
These models were discontinued in 2009, but 64,000 were sold between March 2006 and July 2009. It is not known how many are still in use.


2009 model - did the gas change come in by then?

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Re: How many of us have a bomb in the kitchen?

#62397

Postby gryffron » June 24th, 2017, 12:32 am

CFCs were banned in 1996. So, yes, explosive and unstable chemicals have been in use as domestic refrigerants since at least then.

Gryff

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Re: How many of us have a bomb in the kitchen?

#62642

Postby gryffron » June 24th, 2017, 11:28 pm

FredBloggs wrote:Do you know anyone who ever had a domestic fridge re-gassed?

Yes. It is fairly common for those big American-style jobbies. Some of which actually have refill ports.

There are also firms that will do it for ordinary domestic sealed-coolant fridges. But it is usually a waste of money. It is quite expensive, and by the time the refrigerants need replacing everything else is getting pretty worn out. Rubber door seals, motor bearings, pump seals etc. It's generally about time to simply replace the whole lot.

Gryff

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Re: How many of us have a bomb in the kitchen?

#63333

Postby escalader » June 28th, 2017, 12:30 am

The coolant used is a bit of a red herring if the rest of the appliance is highly flammable.

http://www.london-fire.gov.uk/news/Late ... VLovIWcFFo


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