Automatic sprinklers General

Question 1

The following 3 definitions are used to differentiate
between the various pipework used on a sprinkler
installation. List and define.

Answer 1

(i) Main distribution pipes: main pipes feeding
the distribution pipework,
(ii) Distribution pipes: pipes directly feeding
range pipes,
(iii) Range pipes: pipes on which the sprinklers
are attached either directly or on short arm
pipes which do not exceed 300mm in length

Question 2

State the max area covered by a sprinkler for
LH
OH
HH

Answer 2

LH   21 sq m    
OH   12
HH   9
special risk or storage racks 
9
9
9

Question 3

The number and layout of sprinklers allowed on
range pipes depends on the layout and size of pipe
used, but

Answer 3

does not exceed nine on any one pipe.

Question 4

The number of sprinklers fed by a distribution pipe

is also determined by the size of the pipe, with

Answer 4

maximum of 48 heads fed by one distribution pipe

Question 5

The hazard class of the installation determines

Answer 5

the
area covered by a sprinkler and the distance
between sprinklers on range pipes and adjacent
rows of sprinklers.

Question 6

Sprinkler design usually ensures that some water

Answer 6

will be deflected onto the ceiling and out in a wide
circle which will overlap the distribution from the
next head.

Question 7

The deflector should normally be

between what heights from ceiling

Answer 7

15mm and 150mm below the ceiling and

roofs

Question 8

To ensure that the efficiency of the sprinkler protection
is not diminished a clear space below the
level of the sprinkler deflector is required. The
requirement of the BS/LPC Rules is:

Answer 8

(i) For high piled combustible stock - lm.
(ii) For potable spirit barrel storage - 0.3m.
(iii) For sprinklers above open suspended ceilings
- 0.8m.
(iv) For other than (i), (ii) or (iii) - 0.5m.

Question 9

Why is it important that sprinklers cover all parts of a building
What is the ruling regarding roof space

Answer 9

Sprinklers must cover all parts of a building,
otherwise fire can develop undetected for a
period and become too large for the system to deal
with effectively. Any roof space or floor space
exceeding 800mm in depth must be sprinkler
protected.

Question 10

Label Diagrammatic layout of
the pipework of a
sprinkler installation.

Answer 10

Town mains fed both ends
Supply pipes
Fire Brigade inlet
main distribution pipe
distribution pipe
riser
range pipes

Question 11

Where holes are cut in floors to take machinery 6.4 Extent of sprinkler System
drives, conveyors, chutes and other vertical openings
such as hoists, lifts, elevators, it is important that

Answer 11

a sprinkler head be placed directly above the opening to prevent vertical fire spread

Question 12

Describe Multiple controls

Answer 12

Heat sensitive sealed valve control outlets (Figure
6.2) are used when it is desired to operate small
groups of sprayers simultaneously - hence the
term multiple control.

The heat sensitive device will be a glass bulb or a
soldered link or lever. When this shatters or fuses,
water is delivered to open sprayers which cover
the protected area. An example of a control is
shown in Figure 6.3(1) and an open sprayer in over
Figure 6.3(2). Where simultaneous operation on a
larger scale is required a deluge system (similar to
that shown in Figure 9.5) will be fitted

Question 13

The following are the principal points a firefighter
should bear in mind when fighting a fire in a sprinklered
building:

Answer 13

(i) On arrival at the fire, a member of the crew
should immediately be sent to the main stop
valve so that:
(a) the valve can be opened if found
closed, and
(b) the valve is not closed except on the
express instructions of the incident
commander.

Question 14

On no account should the sprinkler system be

turned off until:

Answer 14

(a) all operating sprinkler heads have been identified,
(b) the incident commander is satisfied that the
fire is under control and can best be tackled
with brigade apparatus,
(c) the incident commander is satisfied that turning
off the sprinkler system will not hinder
the evacuation of people in the building or
put firefighters at ris

Question 15

Many so-called sprinkler failures have been due to

premature closing of the main stop valve. Discuss

Answer 15

A head
opens and apparently extinguishes the fire, the
water supply is cut off in order to prevent further
water damage and the fire which has continued to
smoulder in a hidden place later bursts out again.
The premises being deprived of sprinkler protection,
the fire grows to large proportions, possibly opening a number of heads. Should the valve then
b e reopened the simultaneous discharge of water
from these heads causes a drop in pressure and a
less effective flow from each head.

N.B. A sprinkler system is designed to check an
incipient fire and not to cope with one that has
got away.

Question 16

On arrival at an installation where principal
supplies of water can be augmented through
a fire brigade inlet, then

Answer 16

a pump should be connected
to the inlet ready to increase the pressure
should a large number of heads have
operated.

Question 17

If additional water is needed for a sprinkler system then

Answer 17

it should not be
taken from the main supplying the sprinklers
unless it is of large size. This main will usually
be a branch from a larger town main and pumps should be set into hydrants on the latter,
or on a different main. Local fire brigade
officers should know the layout of mains
supplying sprinkler installations in their
areas.

Question 18

Although a sprinkler may appear to have

extinguished the fire…

Answer 18

careful examination of
the area involved must be made in order to
verify that no trace of fire remains

Question 19

When a fire is out and, for any reason, it is
impossible to turn off the main stop valve
immediately and thereby cut off the flow of
water to the sprinkler head, water damage
can be prevented by

Answer 19

securing the female coupling
of a length of hose over the head and
leading the hose out of the building.