In article , Peter Parry
writes
On Mon, 14 Dec 2009 17:15:50 +0000, Old Git
wrote:

This type is preferably fitted upside down but will work just as well
horizontally. The pressure in the beast will eject all of the foam.
When the foam is exuded it will spread itself out across the
compartment, smothering everything. The pressure and design of the
nozzle will spray most of it across the compartment but also, when the
foam lands, it will continue to spread itself out and smother the
fire. Not sure what the foaming agent is now but at one time it was Ox
Blood.

Ox blood derived foam was the evil smelling yellow Protein Foam.
Aqueous Film Forming Foam is quite different. It doesn't come out as
a thick foam but more like water with a bit of washing up liquid
added. It works by forming a film across the fuel surface so isn't
that good on machinery fires (too many bits sticking out) but really
good on pooled fuel. In an engine room its main use in a fixed
extinguisher is to cover fuel on the floor with extinguishing agent so
spilled fuel does not ignite.

It has the secondary advantage that it is non-corrosive and very
simple to clean off (just rinse with fresh water) so you don't get any
damage from the extinguisher (unlike Protein Foam which started to rot
after a few days and in the bilges would render a vessel uninhabitable
in a week in a warm climate!).

Any comments on the likely success of operation when not inverted?
Having seen the way these heads work in sprinkler systems I'd be
surprised if a satisfactory result came from horizontal mounting. Would
it deploy fully on its side?
--
fred
BBC3, ITV2/3/4, channels going to the DOGs