UNITED FIRE SYSTEMS -
NITROGEN-
PAC™
MODEL SC-W
INSTALLATION, COMMISSIONING, AND MAINTENANCE MANUAL
REVISION 1.01 MAR 2021 - P/N 30-NPWICM-000
22
(d)
As is typical for existing systems, layout drawings and hydraulic calculations may not be available. The last
remaining alternative is to do a field survey of all system piping, by size and length.
1.
Determine accessible pipe lengths with a tape measure. Use
Table 3
to determine pipe volume based on
linear feet of pipe.
2.
When pipe is not directly accessible (such as pipe that is hung overhead, above ceilings, or buried in walls),
attempt to
estimate lengths by “pacing off” each segment. Use
Table 3
to determine pipe volume based on
linear feet of pipe.
Table 3
Gallons Per Foot of Pipe
Based On Nominal Pipe Size and Pipe Schedule
Nominal Pipe
Size
1/2”
3/4”
1”
1-
1/4”
1-
1/2”
2”
2-
1/2”
3”
4”
6”
8”
Schedule 40
Pipe
0.016
0.028
0.045
0.078
0.106
0.175
0.249
0.384
0.662
1.501
2.599
Schedule 10
Pipe
0.190
0.284
0.434
0.741
1.649
2.777
2.6.3. Maximum Volume of Single Largest Riser.
(a)
When the Model SC-W assembly
IS
required to provide 30-minute initial-fill (no additional air compressor), the
maximum volume of the single largest riser is:
1.
500 gallons when the riser supervisory pressure is 20 PSIG or less.
2.
220 gallons when the riser supervisory pressure is over 20 PSIG (up to a maximum of 40 PSIG).
(b)
When the Model SC-W assembly is
NOT
required to provide 30-minute initial-fill (separate new or existing air
compressor), the maximum volume of the single largest riser is 900 gallons.
2.6.4. Maximum Volume of All Risers.
When the volume of each riser has been determined, add these values together
to determine the volume of all risers. The maximum volume of all risers is 900 gallons.
2.6.5. Required Supervisory Pressure.
Different types of sprinkler valves require different values of supervisory
pressure, expressed in PSIG. The maximum supervisory pressure that can be supplied by the Model SC-W
assembly is 40 PSIG.
2.6.6. Type
I
Arrangements
– Model SC-W Assembly for Initial-Fill With Air.
If no additional new air compressor is to
be provided, or if there is no existing air compressor that is to be retained, then the Model SC-W air compressor
must supply the initial-fill capability required by NFPA 13. Refer to
Table 2
for the maximum limits of the Model
SC-W assembly in this circumstance.
2.6.7. Type
II
Arrangements
– External Air Compressor for Initial-Fill With Air.
If a new external air compressor is to
be provided, or an existing air compressor will be retained, then refer to
Table 2
for the maximum limits of the
Model SC-W assembly in this circumstance.
2.6.8. Are Sprinkler Systems NEW or EXISTING?
If the answer is EXISTING, it should be understood that existing
sprinkler systems typically have large leakage rates. NFPA 25 permits a maximum leakage rate of 3 PSIG in 2
hours starting at 40 PSIG. To avoid excessive
NITROGEN-
PAC™
Model SC-W compressor run time and possible
premature compressor failure / replacement, leaks should be corrected until the measured leakage rate does not
exceed 1-1/2 PSIG in 24 hours starting at 40 PSIG.
Содержание Nitrogen Pac SC-W
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