Horrific Fire Engulfs London Apartment Tower

[Strontium Dog]

With the exception of arch self-publicist Lammy, I was unsure why the Labour Party weren't making more capital out of this, until I saw that their councils have been routinely installing the exact same cladding. In fact, Salford council is currently removing it from NINE of its tower blocks.

[rainbow]

As an addendum to the above post, steel melts at about 1370C and to clarify the 'Zinc' confusion, that melts at 419.5C. House and building fires can reach up to 1000C or more. The damage at Grenfell and the pictures of the conflagration certainly indicates, to my mind, temperatures up to and possibly exceeding 1000C.

Metro

Using cladding made from the same materials as that in Grenfell Tower, they went to a laboratory to carry out tests.

There, the materials were heated to 700°C for two minutes – the fire at Grenfell reached temperatures of more than 1,000°C.

Melting point isn't the only issue.
The heat capacity of aluminium is nearly twice that of steel, so it takes about as much energy to get it to 700°C as it does to get steel to 1370°C.

[JimC]

As an addendum to the above post, steel melts at about 1370C and to clarify the 'Zinc' confusion, that melts at 419.5C. House and building fires can reach up to 1000C or more. The damage at Grenfell and the pictures of the conflagration certainly indicates, to my mind, temperatures up to and possibly exceeding 1000C.

Metro

Using cladding made from the same materials as that in Grenfell Tower, they went to a laboratory to carry out tests.

There, the materials were heated to 700°C for two minutes – the fire at Grenfell reached temperatures of more than 1,000°C.

Melting point isn't the only issue.
The heat capacity of aluminium is nearly twice that of steel, so it takes about as much energy to get it to 700°C as it does to get steel to 1370°C.

However, that heat capacity (897 joules/degree/kg for Aluminium, vs 449 for steel) is, as the unit suggests, energy per kilogram. Given that the density of steel is over 3 times that of Aluminium, the energy required (depending on volumes, of course) will at least even out. The mass of Aluminium in any metal-surfaced cladding will certainly be lower than the equivalent in steel or zinc - weight reduction would be one of the design parameters...

[rainbow]

As an addendum to the above post, steel melts at about 1370C and to clarify the 'Zinc' confusion, that melts at 419.5C. House and building fires can reach up to 1000C or more. The damage at Grenfell and the pictures of the conflagration certainly indicates, to my mind, temperatures up to and possibly exceeding 1000C.

Metro

Using cladding made from the same materials as that in Grenfell Tower, they went to a laboratory to carry out tests.

There, the materials were heated to 700°C for two minutes – the fire at Grenfell reached temperatures of more than 1,000°C.

Melting point isn't the only issue.
The heat capacity of aluminium is nearly twice that of steel, so it takes about as much energy to get it to 700°C as it does to get steel to 1370°C.

However, that heat capacity (897 joules/degree/kg for Aluminium, vs 449 for steel) is, as the unit suggests, energy per kilogram. Given that the density of steel is over 3 times that of Aluminium, the energy required (depending on volumes, of course) will at least even out. The mass of Aluminium in any metal-surfaced cladding will certainly be lower than the equivalent in steel or zinc - weight reduction would be one of the design parameters...

...unless the steel is thinner than the aluminium, which it can be since it is stronger.

Just saying the problem is more complicated than the melting point of the materials used.

[JimC]

Yes, there are many factors, but the flammability of the inner insulating material is still the key.

[Alan B]

The use of the word 'Zinc' in this context is misleading - no panels are made of 'Zinc' or its alloys. Zinc is purely a corrosion prevention plating for steel and will play no part (or at the most, a minuscule part) in the thermal properties of steel.

[Alan B]

Yes, there are many factors, but the flammability of the inner insulating material is still the key.

Undoubtedly.

[JimC]

The use of the word 'Zinc' in this context is misleading - no panels are made of 'Zinc' or its alloys. Zinc is purely a corrosion prevention plating for steel and will play no part (or at the most, a minuscule part) in the thermal properties of steel.

I would love to know the dimensions and mass of the zinc-coated steel panels vs the aluminium panels. With those facts, one could speak more accurately about the issues rainbow and I were debating...

[mistermack]

Aluminium might have a higher specific heat, but it CONDUCTS heat better than steel.
If you have a mixture of aluminium and steel saucepans, the ally ones heat up the contents quicker.
My good stainless steel saucepans have copper bottoms, because of that property. I have a crap old SS one for baking potatoes, with a steel base, and it is very slow for heating liquids.

That's what I find. It might be bollocks, but I can't be bothered to check it.

You also have the problem of weathering, and SS is expensive, and coatings only last so long on carbon steel.

I think the problem with the filler insulation is going to be the rate at which it emits flammable gases under typical fire conditions.
You can put barriers in to prevent the internal chimney effect, but gas will always get out, and heat rises, so attempts to mitigate the problem will never match using materials that emit less flammable gases in the first place.

If cost really WAS a huge problem, you could use non flammable panels directly above the windows of each flat, and use the flammable ones everywhere else. So, if a fire happens, the panel above the window won't catch fire.
That in itself would probably have prevented the London tower block fire from being any worse than a single flat fire.

[rainbow]

The use of the word 'Zinc' in this context is misleading - no panels are made of 'Zinc' or its alloys. Zinc is purely a corrosion prevention plating for steel and will play no part (or at the most, a minuscule part) in the thermal properties of steel.

I would love to know the dimensions and mass of the zinc-coated steel panels vs the aluminium panels. With those facts, one could speak more accurately about the issues rainbow and I were debating...

Galvanized sheeting, that is mild steel with a few microns of zinc on its surface, would probably be 0.5mm
Aluminium sheeting would probably have to be 1 mm thick, but it would still be a tad lighter.

[rainbow]

Aluminium might have a higher specific heat, but it CONDUCTS heat better than steel.

Probably a benefit as it would take heat away from the fire.

[mistermack]

Aluminium might have a higher specific heat, but it CONDUCTS heat better than steel.

Probably a benefit as it would take heat away from the fire.

I think probably not, as the heat would reach the flammable internal insulation easier, and cause it to out-gas sooner and faster.
It would be the escaping gases that spread the fire, as the metal covering would be pretty effective keeping oxygen away from the insulation, for a reasonable period at least.

[Alan B]

In this picture of the outside of Grenfell Tower, it looks as though there are just remains of the burnt insulation where the panels used to be. The Aluminium sheets seem to have disappeared, either melted or dropped off. I suspect the latter - as soon as the panels heated up, the bond holding the Aluminium sheet to the insulation ruptured thus releasing the sheet and allowing the insulation further access to the flames.
This would seem to indicate that there were no other metal fixings securing the front and back Aluminium sheets as part of the 'sandwich'.

from the Independent

[JimC]

If the panels were full of something like rock wool (the non-asbestos type, obviously), there would not be an issue. Probably dearer, and a bit heavier...

[mistermack]

Fit the panels with sprinklers.