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138

T

Table 46: Distribution pipe diameters in OH installations (G10)

Distribution

pipes

Layout

Diameter mm

Maximum number

of sprinklers

fed

At

extremities of

system

2

end-side

All

others

32

40

50

65

32

40

50

65

2

4

8

16

3

6

9

18

Between

design

points

and

the

control

valve

set

All

To

be

calculated

in

accordance

with

G.2.4.2

When

the

ranges

run

longitudinally

under

roofs

sloping

at

an

angle

of

more

than

6°,

the

number

of

sprinklers

on

a

range

pipe

shall

not

exceed

6.

The

use

of

65mm

diameter

pipe

between

the

design

points

and

the

control

valve

set

is

permitted

provided that

a

hydraulic

calculation

shows

this

to

be

possible.

NOTE:

figure

H4

gives

an

example

of

a

pipe

layout

in

OH

with

the

appropriate

design

points

from

which

the pipe

diameters

shall

be

fully

calculated.

G.2.4.2

The

pipe

diameters

between

the

design

point

in

the

most

remote

area

of

the

installation

and

the control

valve

set

shall

be

calculated

to

ensure

that

the

total

pressure

loss

due

to

friction

with

a

flow

of

1000l/min

does

not

exceed

0,5bar,

except

modified

in

G.2.4.3

and

G.2.4.4.

G.2.4.3

In

buildings

with

a

number

of

floors,

or

where

there

are

a

number

of

different

levels,

e.g.

:

platforms

or

lean-to’s,

the

0,5bar

loss

in

pressure

from

the

design

point

on

each

floor

may

be

increased

by

an

amount equivalent

to

t

he

static

pressure

due

to

the

height

difference

between

the

highest

level

and

the

floor concerned.

In

these

cases,

the

height

difference

between

the

highest

sprinkler

level

and

the

installation

pressure

gauge shall

be

indicated

on

the

completion

certificate,

together

with

the

pressure

required

at

the

installation pressure

gauge.

G.2.4.4

Where

the

same

system

includes

both

OH3

or

OH4

and

HHP

or

HHS

areas,

all

connected

to

a common

water

supply,

the

maximum

friction

loss

of

0,5bar

may

be

increased

by

50%

of

the

available

extra pressure,

as

indicated

in

the

following

example

for

OH3.

Example:

Pressure

required

at

the

control

valve

set

excluding

static

pressure

(Table

6

for

OH3)

1,4bar

Pressure

difference

due

to

the

difference

in

height

between

the

highest

sprinkler

and

the

control

valve

set

1,2bar

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