Automatic sprinklers Protection of special risks Flashcards
What does HPS stand for
High packed storage
The high-bay (or high racked) warehouse presents
a particularly difficult type of fire risk because of
Size
Height
Variety of goods
Close packed proximity of goods
What obviates regular fused and glass bulb sprinklers
Flames tend to pass a sprinkler location
before its actual operation and ignite goods at a
higher level, mainly due to the flue effect of the
racking layout.
Regarding HPS an in-rack system incorporating a ‘fast response’
head has proved more
effective, especially when allied to recommendations
on construction of the racking and positioning
of heads.
These recommendations include:
(i) Range pipes located at alternate levels: i.e. 2,
4, 6, etc, the top level being covered by a
pipe above it.
(ii) Fast response sprinklers located above the
junction of transverse and longitudinal flues,
pendant-mounted and incorporating a specially
designed water-deflecting shield.
(iii) A non-combustible covering (rack capping)
located above the top level of goods with a range pipe and sprinklers located immediately
below it.
(iv) Partial capping of the side of the rack and the
space between the end pallet position and the
end of the rack.
(v) In very high storage, e.g. over 15m, intermediate
rack capping to be considered with
pipes and sprinklers underneath it.
(vi) Certain minimum aisle widths to be maintained.
(vii) The division of the protected area into a
number of zones such that within each individual
zone, all sprinklers operate together.
(viii) The hydraulic design of the system should be
adequate for the height and area of each protected
zone in the worst incident.
High-piled storage (HPS), as found in these warehouses,
comes under the High Hazard category
(see Section 1.4.3). For each of the sub-categories
I-IV the BS/LPC have specified minimum densities
of water application based on hydraulic calculation.
They consider, however, that there is a
difference between HPS ….
Explain
freestanding storage
HPS palletised-rack storage.
freestanding goods tend
to break apart, allowing water to penetrate the stack.
This does not readily happen in palletised rack storage
and BS/LPC consider that this warrants an
increased water density to protect it against fire
The specified minimum density of water application differs between Free standing and Palletised how ?
(palletised) have their category increased by one-half except in the case of Group IV. Group IV requirements for water discharge density is already very large.
Examples of goods in HPS categories are
Category I - Wool carpets, textiles, electrical apparatus
Category II - Baled waste paper, chipboard,plastics (non-foamed), wooden furniture
Category III - Wax-coated paper, foamed plastics
rubber goods,
Category IV - Offcuts of foam plastic, sheet foamed plastic, celluloid, foamed rubber
Protection of aircraft maintenance and assembly
areas presents special problems, especially when
dealing with fires under the large wing areas of
modern commercial aircraft
How is this overcome
hangar is fitted with sprinkler nozzles in the floor
The area
is divided into zones and each zone contains an
average of 110 sprinklers
supplemented
by wall-mounted, over-wing oscillating jets
whole system is actuated by automatic radiation
fire detectors.
The extinguishing agent is Aqueous Film Forming
Foam (AFFF
The sprinklers each produce vertical
jet at least 5m high plus three peripheral jets
giving a ground spray about 8m in diamet
