UNITED FIRE SYSTEMS -
NITROGEN-
PAC™
MODEL SC-W
INSTALLATION, COMMISSIONING, AND MAINTENANCE MANUAL
REVISION 1.01 MAR 2021 - P/N 30-NPWICM-000
21
2.6 Ensuring NITROGEN-
PAC™ Model SC-W is Appropriate for the Sprinkler System in Use.
Refer to
Table 2
.
The Model SC-W assembly must meet or exceed all applicable limits determined by the survey.
Table 2
Maximum Limits
– NITROGEN-PAC™ Model SC-W Assembly
WHEN SC-W IS
REQUIRED
TO PROVIDE INITIAL-FILL (TYPE
I)
MAXIMUM
NUMBER OF
RISERS
MAXIMUM VOLUME
OF ALL RISERS (IN
GALLONS)
SINGLE LARGEST RISER (IN GALLONS)
UP TO 20 PSIG SUPERVISORY
PRESSURE
UP TO 40 PSIG SUPERVISORY
PRESSURE
2
900
500
200
WHEN SC-W IS
NOT REQUIRED
TO PROVIDE INITIAL-FILL (TYPE
II
)
MAXIMUM
NUMBER OF
RISERS
MAXIMUM VOLUME
OF ALL RISERS (IN
GALLONS)
SINGLE LARGEST RISER (IN GALLONS)
UP TO 20 PSIG SUPERVISORY
PRESSURE
UP TO 40 PSIG SUPERVISORY
PRESSURE
2
900
900
900
2.6.1. Maximum Number of Risers.
The maximum number of risers protected by one (1) Model SC-W assembly is two
(2). If the number of risers exceeds two (2), use multiple Model SC-W assemblies, or another choice of
NITROGEN-
PAC™
system from
UNITED
Fire Systems
.
2.6.2.
Determining Volume (In Gallons) of Each Sprinkler Riser.
Determining the actual volume (in gallons) of
each sprinkler riser is necessary to ensure that the Model SC-W assembly is appropriate for the installation
being considered.
IMPORTANT
The pipe vol
ume is a fundamental parameter that MUST be determined. If a relatively “inaccurate” method of
determining length (such as “pacing off”) must be used, make sure that the pipe volume is not underestimated.
Underestimating the pipe volume can result in:
1. Not meeting the 30-minute initial-fill requirement.
2. Greatly extended compressor run time, and shortened compressor life.
3. Not reaching or maintaining 98% nitrogen purity in the piping.
4. Not maintaining minimum pipe pressure, resulting in unwan
ted “low air” signals.
WHEN IN DOUBT, OVERESTIMATE!
One of several methods may be used.
(a)
Examine the system layout drawings for completed pipe volume calculations.
(b)
Examine the system hydraulic calculation results for completed pipe volume calculations.
(c)
Use the system layout drawings to do a “takeoff” of the sizes and lengths of all piping connected to each riser.
Use
Table 2
to determine pipe volume based on linear feet of pipe.
Summary of Contents for Nitrogen Pac SC-W
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