Fireproof safe

"John L. Weatherly" fired this volley in news:FqSdnW8YSO2hBBranZ2dnUVZ snipped-for-privacy@cavtel.net:

Prob'ly would, but it is pretty much standard practice to line "fireproof" stuff with low-strength, highly aerated gypsum; the thicker, the better.

Most (even inexpensive) home-quality firesafes still have over a full inch of gypsum between the walls. A one hour fire rating isn't all that hard to achieve.

Kaowool would be overkill in terms of cost -- how about boiler liner sheets, instead? They're better insulators than gypsum, and just about dirt cheap.

LLoyd

I am a locksmith, and the insulation in fire safes is designed to hold moisture until heated and then it releases it into the interior compartment of the box. I had a customer that stored his ammo in a fire file in his garage.

While he was on a camping trip, the car in his garage had developed a leak in the gas tank and when the fumes built up to the pilot for the water heater BOOM!! The garage door was blown across the street and over the neighbors roof ending up in their pool in the back yard.

His Snap On tools had annealed from the intense heat, but when he opened the file after the fire, the plastic boxes were not melted in the slightest.

Fires get very hot, the Kaowool type insulation does not serve well in that kind of heat for the length of time needed.

The reason they use " drywall " is that it has a lot of water in it bound in the material. On prolonged heating the water is driven out and the " drywall " turns to powder. This takes a bunch of btu's to do this. So while Kaowool would keep the heat from getting in, it would not do as good a job at keeping the contents cool.

Dan

Did this customer, per chance, fix his punctured tank with a wooden plug, prior to the accident? :)

i

No, Kaowool is an insulator, but only an insulator. The lining in a firesafe contains a significant quantity of water too, bound up as hydrated lime compounds in this "drywall". When you burn the safe, this water is released and boiling it off absorbs heat energy. Overall, this keeps the contents cooler than Kaowool alone would.

Obviously this is a transitory condition. It only works for as long as there's water to release. This is why firesafes with thick or thin walls are rated for diifferent _durations_ of fire, not necessarily temperatures.

It's also a little more sophisticated than plain drywall, although drywall is itself quite a good fire barrier in house construction. The chemistry of firesafes like this goes back to the early Victorian period - there are safe sites on the web that describe the inventors and their patents in detail.

So the material they line the safes with is lime, rather than gypsum?

-- Ed Huntress

Nothing is fireproof. As you may have noticed, you can improve your home security container by lining it with dry wall on the outside.

Wes

I'm sure hoping not. Gypsum CaSO4·2H2O Lime CaO

ROTFLMAO

I'll bet you know I was shorthanding for hydrated lime, or calcium hydroxide, Ca(OH2).

Hydrated lime is what plaster walls were once made of (as in the walls in my house). Drywall is semi-hydrous calcium sulphate, or gypsum. Either one will ablate, or give of combined water, when it's heated. I was just curious about whether the actual stuff used to line safes was the same gypsum board used for walls, or something special made from hydrated lime.

-- Ed Huntress

Milner's original fireproof patent was for about 4" of sawdust, kept wet!

"Lime" in en_GB speak is generally hydrated lime, not CaO. That's termed "quicklime". It's crucial to the fireproofing that this would be "slaked" lime (i.e. hydrated), not quicklime.

The stuff used is safes has varied. As was typical for Victorian innovations, much of the "innovation" was driven by trying to dodge around other peoples' patents, so much as choosing materials for their own sake. Both lime (carbonate) and gypsum (sulphate) compounds have been used, also alum (aluminium / potassium sulphate, rather than calcium sulphate).

Thanks, Andy. There's *another* topic for cocktail party conversations I've learned from this group. You should see how I get them going by talking about wiring for three-phase motors!

-- Ed Huntress

I'll bet you mean Ca(OH)2.

Hydrated lime is *part of* what plaster walls *are still* made of, among other constituents including sand, portland cement, perlite or vermiculite, and (in bygone days) often horsehair.

OK, somebody was bound to get technical. My walls are a three-layer job: scratch coat over wood lath, with horsehair; brown coat; and finish coat. Almost all of the original is still there, although I've done some patching. I no longer finish with slaked lime, however, when I have to fix something. It takes too long to cure.

-- Ed Huntress

Yep, that would work. Construction adhesive is your friend. Actually, I used a combination of brick and patio stones on the outside if mine, and then covered the ooutside in ceramic floor tile. My goals (both equally important) were to improve the fire resistance of the safe, while at the same time rendering it immobile.

Vaughn

That is an intresting concept. " lining on the outside " . Havent seen that done yet. :-) All the linings I've ever seen or heard of have been on the inside. Oh well another (you know what I mean) ...lew...

Standard practice in the UK. Not on the "outside outside", but if you have a garage space that's inside the outside walls of a house, you need a couple of layers of drywall (aka plasterboard) fastened up on the _fire_ side of the structure. And that's for our style of house construction with real bricks too, not US ticky-tacky boxes!

If your houses are built with real bricks, why do you need fire protection? Do you make your bricks out of wood chips?

-- Ed Huntress

Having read most of the posts on this thread it reminded me of looking into fire safes for protection of data stored on computer storage media. This brought up the difference between a fire safe intended for the protection of paper or other items which could stand upto temps of

150C or more without damage, a machinist I knew stored all his gear cutters in a large old firesafe, and a data safe intended for the storage of digital media that might be damaged at temps much above 40C. Does anyone have any idea of the mechanism used to keep the internals of a data safe at a safe low temp compared to the mechanisms used in a fire safe which seem to be using the heat taken by removing the water of hydration from gypsum and the like.

A company I worked for in the past might be in for a shock if the had a fire as they had the server hard drive in a cheap firesafe on the end of the ribbon cable, might not have fared well but luckily I don't think it has been tested.