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 CHAPTER 3. STEAM DISTRIBUTION
Section 1. APPLICATIONS AND SYSTEMS
I HEAT TRANSMISSION. S t e a m conveys heat energy to distant points. The
amount of heat that steam can transmit depends on its temperature and
p r e s s u r e . Saturated steam temperature depends on steam pressure. The total
heat content of a pound of steam increases with a rise In pressure, from
a t m o s p h e r i c pressure (14.7 psia) up to about 410 psig. Above 410 psig, the
t o t a l heat of steam decreases as pressure increases. Direct buried conduit
s y s t e m s shall be installed, maintained, and repaired in accordance with the
Manufacturer's Approved Brochure and NAVFAC Guide Specifications NFGS-15705,
U n d e r g r o u n d Heat Distribution Systems (Prefabricated or Pre-Engineered
Types). Systems shall have a Letter of Acceptability issued by Federal Agency
Committee on Underground Heat Distribution Systems. The Letter of
A c c e p t a b i l i t y is signed by representatives of federal agencies participating
i n the committee and stating that the supplier's system is approved for use
f o r the site ground-water conditions, operating temperature, and soil
c l a s s i f i c a t i o n ( s ) indicated. Shallow concrete trench systems shall be
installed in accordance with NFGS-15751, Heat Distribution System Outside of
Buildings (Concrete Shallow Trench Type). As energy costs continue to
r i s e , proper operation, maintenance and repair becomes more and more cost
e f f e c t i v e to implement in an expeditious manner.
E n g i n e e r i n g Field Divisions
s h a l l assist and Activities shall assure that efficient operation and timely
maintenance of steam distribution systems are performed. The Power Principles
V i d e o Training Program shall provide further assistance to all concerned.
2 STEAM DISTRIBUTION SYSTEM. Consumers may be located in several buildings
o r a group of buildings where steam is required for space heating and/or
process work. For purposes of this manual, a steam distribution system
c o n s i s t s of the following equipment:
S t e a m piping required to transport steam from a central steam
generating plant to consumers
P i p i n g required to return condensate to the generating plant
E q u i p m e n t , instrumentation, a n d r e l a t e d f a c i l i t i e s r e q u i r e d t o
serve the above described purposes
3 SUPPLY PRESSURE. Steam supply systems are categorized as either low-
pressure systems or high-pressure systems.
3.1 Low-Pressure Steam. Low-pressure steam, O to 15 psig, is used for space
h e a t i n g (unit heaters, radiators, connectors, heating coils, or other steam
h e a t i n g devices), snow melting, c o o k i n g , and domestic hot water heating. It
i s distributed from a central plant or mechanical room to a multiple building
installation.
The advantages of low-pressure vice high pressure steam are:
S m a l l distribution losses, due to the relatively low temperature of
the steam
S m a l l e r losses and trouble from leakage, traps, and venting
3-1
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