CEA 4001 - Page 55

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The pressure tank shall be housed either in a readily accessible position in a sprinkler protected building or in
a separate sprinkler protected building of non-combustible construction used solely for the housing of fire
protection
water supplies and equipment. When the pressure tank is housed in a sprinkler protected building
the area shall be enclosed by fire resistant construction of no less than 30 minutes.
The pressure tank and housing shall be maintained at or above a temperature of 4°C.
8.5.3 Minimum capacity (water)
The minimum quantity of water in a pressure tank for a single supply shall be 15m
3
for LH and 23m
3
for
OH1.
The minimum quantity of water in a pressure tank for duplicate supplies shall be 15 m
3
in LH and OH (all
groups).
8.5.4 Air pressure and contents
8.5.4.1 General
The air space shall not be less than one third of the pressure tank volume.
Pressure in the tank shall not exceed 12 bar.
The air pressures and water flow rates from the tank shall be sufficient to satisfy the sprinkler installation
demand
requirements, up to the point of exhaustion.
8.5.4.2 Calculation
The air pressure to be maintained in the tank shall be determined from the following formula:
V
t
P = (P
1
+ P
2
+ 0 , 1h ) ___ - P
1
V
a
where:
P is the gauge pressure, in bar;
P
1
is atmospheric pressure, in bar (assume P
1
= 1);
p
2
is the minimum pressure required at the highest sprinkler at pressure tank exhaustion, in bar. For
precalculated systems this value shall be taken from Tables 7 and 8, plus any additional pressure
losses between the control valve set and pressure tank (Table 7) or between the design point and
pressure
tank (Table 8), but ignoring static pressure;
h is the height of the highest sprinkler above the bottom of the pressure tank (i.e. negative if the
highest
sprinkler is below the tank), in metres;
V
t
is the total volume of the tank, in cubic metres; V
a
is the volume of air in the tank, in cubic metres.
8.5.5 Charging with air and water