On 04/10/2020 12:58, Chris Hogg wrote:
On Sun, 4 Oct 2020 12:34:51 +0100, nightjar wrote:

On 04/10/2020 12:15, JohnP wrote:
A school has just gone up in flames in my area. Usual photos of it burning
inside whilst water is put on the outside. Usual cries for sprinklers - but
these can be vandalised and could cause problems.

I know about dry risers - usually to Landing Hose Unions - but what about a
simple array of pipes in the roof space with open nozzles. In the event of
a fire then the Fire Engine hooks up and dowses the fire from the inside
using the fixed nozzles - no need to enter the building. Notre Dame would
have possibly been saved if such a simple system was in place.

Any thoughts? It seems a compromise to a full sprinkler system but has the
advantage of not being automatic and able to flood the building.


Unlike a sprinkler system, which releases water only in the vicinity of
the fire, that would release water throughout the building. Fine if the
whole building is on fire, but it could result in unnecessary water
damage if the fire were only localised.

There are dry sprinkler systems. They contain compressed air or
nitrogen, but they still need a detector head to activate. That releases
the gas which, in turn, activates a valve that allows water to enter the
system.

IIRC large electrical installations such as large switch rooms in
basements etc have CO2 cylinders installed and ready to be discharged
in case of fire, thereby depriving the fire of oxygen but not
electrocuting anyone by throwing water around. But there's the danger
of suffocation if the system goes off and there's someone trapped
nearby.


Although, in the case of a dry sprinkler system, the gas is not pat of
the fire suppression system. It simply keeps the pipework under pressure
until a sprinkler head is activated. The drop in pressure releases a
valve that allows water into the pipework. They are mainly used in
unheated areas where there is a risk that, if the pipes were kept full
of water, it could freeze.

--
Colin Bignell