User's Manual

Design
September 2013 3-54 P/N 81-CO2MAN-001
3-9 PRESSURE OPERATED SIRENS
Pressure Operated Sirens, Part No. 81-981574-000, necessarily discharge carbon dioxide to
operate. When this discharge does not contribute to a firefighting concentration (i.e., within a
total flooding hazard), the total system agent quantity must be compensated to account for
the carbon dioxide discharged by the siren. Operation of the siren requires 20.4 lb./min. (9.3
kg/min.).
(Equation 32)
(US Units)
or
(Metric Units)
Where:
= Minimum agent discharged through pneumatic siren, lb. (kg)
= Quantity of Pressure Operated Sirens
= Total system discharge time (liquid and vapor), min
= Pneumatic delay time, min
EXAMPLE 14 - PRESSURE OPERATED SIRENS - Siren Agent Discharge
Consider a combination system with a Pressure Operated Siren located inside the total
flooding hazard and one located outside. A 30-second Pneumatic Discharge Delay will provide
a pre-discharge alarm period. Determine the additional quantity of agent that is needed to
compensate for losses through the sirens.
From Equation (32):
Where is the Quantity of Pressure Operated Sirens, is the Discharge Time, and is the
Pneumatic Delay Time.
Since only one siren is located outside the total flooding hazard:
= 1
From Equation (31):
Where is the Duration of Liquid Discharge of the Local Application Portion.
From Paragraph 3-6.1.3:
= 30 s
= 0.5 min
W
s
20.4 nt
d
 t
p
+=
W
s
9.3 nt
d
 t
p
+=
W
s
n
t
d
t
p
W
s
20.4 nt
d
 t
p
+=
n
t
d
t
P
n
t
d
1.4 t
liq
=
t
liq
t
liq
t
liq