Amd 3 and plastic wall plugs

[JohnW2]

I suddenly remembered that I've seen (and possibly used ?) in the past a metal equivalent to the plastic wall plug. And on checking, I see that there are indeed such things still available. So in that respect, if the question is whether the plastic plug in the wall is a weak spot in a fire, then metal ones are available and therefore don't need any changes in working practices to use.

Yes, although I don't recall ever having seen quite that, it occurred to me that a 'metal equivalent to the plastic wall plug' should be very possible. One imagines that a 'tube' of a soft metal would do much the same job. As well as being expensive (and toxic) lead (which would probably otherwise be the ideal) would probably melt too easily, but thin aluminium would probably work OK.

Kind Regards, John

 

[SUNRAY]

Yes, although I don't recall ever having seen quite that, it occurred to me that a 'metal equivalent to the plastic wall plug' should be very possible. One imagines that a 'tube' of a soft metal would do much the same job. As well as being expensive (and toxic) lead (which would probably otherwise be the ideal) would probably melt too easily, but thin aluminium would probably work OK.

Kind Regards, John

Lumps of lead rammed into holes with a drift has certainly been a system for many years, usually to receive nails.

As you say the melting point is quite low though.

 

[John D v2.0]

It would be a combination of melting point and thermal inertia.
I think this is why the BRE did their experiments with concrete blocks, to take account of the heat buffering. The block temp didn't actually get that high considering the fire temperature.
Premature collapse is just referring to a comparison with the rest of the building elements, so with half hour or one hour fire board, the cables don't really need to last longer.
I think a clear spec would help, as this thread illustrates how performance specifications leave everyone in doubt, people just want to know what to buy.

 

[JohnW2]

I think a clear spec would help, as this thread illustrates how performance specifications leave everyone in doubt, people just want to know what to buy.

Quite so.

Regulations requiring "a suitable X", "adequate protection against Y" etc. etc. are hardly 'regulations' to my mind.

Kind Regards, John

 

[SimonH2]

Would they be Alex Plugs? post#12

They're the ones I remember - but not the ones I found with a quick search. Several places sell steel ones, it looks like Alex plugs are still made but not stocked widely (at least in the UK).
I see the melting point of aluminium is 660˚C, and alloy between 463 and 671 ˚C (https://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html) which I would imagine would be high enough that by the time it's let go, I doubt if anyone is going to be at all bothered. Higher than the melting points for lead, tin, zinc - so your soldered joints will have let go, as will the galv on the trunking and conduit.
But then I've seen photos of (for example) ships' engine rooms after a fire - and things like aluminium rocker covers are more or less completely missing

 

[JohnW2]

I see the melting point of aluminium is 660˚C, and alloy between 463 and 671 ˚C ... which I would imagine would be high enough that by the time it's let go, I doubt if anyone is going to be at all bothered.

Indeed, and I'm not sure there would be much of the building left by the time the temp within a masonry wall got to that temperature.

At least until new-fangled materials came along, aluminium/alloys were used extensively in aircraft (because of their low weight) - and if it was considered good enough for aircraft, I'm be inclined to say that it is probably good enough for wall plugs!

Kind Regards, John