UFC 3-240-13FN
25 May 2005
CHAPTER 5
CLOSED INDUSTRIAL WATER SYSTEMS
5-1
DEFINITION. The term "closed water system" refers to a water system
that is used to provide heating, cooling, or both for industrial processes or facilities. The
system is sealed (closed), sometimes under pressure, and is not open to the
atmosphere. No evaporation takes place and, with good operation, water is lost only
minimally from the system. In general, water treatment for closed systems is much
easier than for open systems. Makeup water is needed only to replace seal leakage and
other incidental leakage. Because of the small makeup water requirements of these
systems, they require little chemical treatment, which can be added intermittently as
needed. Once properly treated, the system water does not form scale and has little or
no corrosion potential. Two main types of closed water systems are used at military
installations: hot water closed heating systems and chilled water closed cooling
systems.
5-1.1
Hot Water Heating Systems. Hot water heating systems are designed to
produce hot water, and although they are often referred to as hot water boilers, they are
systems are preferred over steam systems. Hot water heating systems, also known as
hydronic heating systems, recirculate water to distribute heat in facilities. They operate
at three temperature ranges:
High-temperature water systems (pressurized systems with water
temperatures higher than 177 C [350 F]) no steam, only very hot
water.
Medium-temperature water systems (pressurized systems with water
temperatures from 121 to 177 C (250 to 350 F]) no steam, only quite
hot water.
Low-temperature water systems (water temperatures lower than 121 C
[250 F]) no steam, only hot water.
5-1.1.1
Hot Water Boilers. Hot water boilers can be either direct-fired (heated by
combustion of gas, oil, or coal) or unfired (heat supplied by steam from a steam boiler,
heated by hot water from a higher-temperature hot water system, or heated by a solar
energy system). For many applications, hot water boilers are preferred over steam
boilers because there are essentially no makeup water requirements and chemical
treatment programs are less complex and easier to maintain. They require less
manpower for operation, less maintenance, and have fewer water-related problems
than steam boiler systems. Figure 5-1 shows a hot water boiler.
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