UNITED FIRE SYSTEMS -
NITROGEN-
PAC™
MODEL SC-W
INSTALLATION, COMMISSIONING, AND MAINTENANCE MANUAL
REVISION 1.01 MAR 2021 - P/N 30-NPWICM-000
1
1. GENERAL INFORMATION
1.1. GLOSSARY.
All glossary terms are defined in reference to their use in this manual. Refer to this glossary for
definitions of unfamiliar terms encountered when reading and using this manual.
Air.
Air is the naturally occurring gas making up Earth’s atmosphere. Air consists of a mixture of gases, of which two
predominate (refer to the glossary terms Nitrogen and Oxygen).
Compressed Air.
Compressed air refers to the output of the
NITROGEN-PAC
™
compressor. This air has NOT
been conditioned for filtering and nitrogen separation.
Pressure Dew Point.
The temperature at which the water in a compressed gas at given pressure condenses into
liquid water at the same rate at which it evaporates. At temperatures below the pressure dew point, liquid water will
leave the gas. At temperatures above the pressure dew point, liquid water will be taken up by the gas.
Dried Compressed Air.
Dried compressed air refers to the output of the
NITROGEN-
PAC™
Model SC-W assembly
intercooler. This compressed air has been conditioned for entry into the separator membrane.
Microbiologically Influenced Corrosion (MIC).
Microbiologically influenced corrosion (also known as MIC)
occurs inside steel dry and preaction sprinkler pipes in the presence of certain microbes. This form of corrosion
causes thinning of pipe walls, possibly leading to failure under water pressure. Pinhole leaks can occur, leading to
water damage. Roughening of the internal pipe surface leads to unpredictable hydraulics, impairing the effectiveness
of the sprinkler system. The tubercles formed by the microbes can loosen, clogging sprinkler heads and impairing or
preventing the discharge of water onto a fire. MIC microbes can be aerobic, growing in the presence of oxygen, or
anaerobic, not needing oxygen but growing in the presence of water. Prevention of MIC results in longer life and
better functionality of the sprinkler system. MIC can be inhibited by using nitrogen to displace oxygen and dry out the
inside of the pipe.
Nitrogen (N
2
).
Nitrogen is a naturally occurring diatomic gas present in Earth’s atmosphere at a concentration of
approximately 78
% (v/v). All references to “nitrogen” in this manual are the output from the nitrogen outlet of the
Model SC-W assembly. This outlet delivers gas that is at least 98% (v/v) nitrogen, at a pressure dew point of
approximately -40°F. The pressure dew point of nitrogen is much lower than of compressed air, making nitrogen
much more effective at drying out the inside of a sprinkler pipe.
Oxidation Corrosion.
Oxidation corrosion (also known as rust) occurs inside steel dry and preaction sprinkler pipes
in the presence of oxygen and water. This form of corrosion causes thinning of pipe walls, possibly leading to failure
under water pressure. Pinhole leaks can occur, leading to water damage. Roughening of the internal pipe surface
leads to unpredictable hydraulics, impairing the effectiveness of the sprinkler system. Loose rust particles can clog
sprinkler heads, impairing or preventing the discharge of water onto a fire. Prevention of oxidation corrosion results in
longer life and better functionality of the sprinkler system. Oxidation corrosion can be inhibited by using nitrogen to
displace oxygen and dry out the inside of the pipe.
Oxygen (O
2
).
Oxygen is a naturally occurring diatomic gas present in Earth’s atmosphere at a concentration of
approximately 21% (v/v). Oxygen is vented from the Model SC-W assembly after being separated from dried
compressed air by the separator membrane.
Purging.
Because of its low dew point, the nitrogen introduced into the sprinkler piping by the
NITROGEN-
PAC™
system absorbs liquid water. To ensure complete drying of the pipe interior, saturated nitrogen within the pipe must
be replaced by dry nitrogen. Purging ensures that this process occurs.
Summary of Contents for Nitrogen Pac SC-W
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