Page 60 - Boiler plant and distribution system optimization manual
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Chapter 5
Distribution System Efficiency
STEAM SYSTEM LOSSES more energy lost in the distribution system, the
more energy wasted by the boiler replacing it.
The steam system is ideal for moving energy When energy losses in the steam distribu-
through piping. No pumps are needed because tion system are corrected, boiler plant losses are
when the latent energy in the steam is expended reduced too.
it condenses to approximately 1/700 of its orig- The steam distribution system moves the
inal volume causing instant replacement of the steam from the boiler to perform work at some
use steam. This replacement steam flows to fill distant location. They do not usually exist sepa-
the volume of the steam which has condensed, rately and they work together to establish a com-
often reaching velocities of 8,000 to 12,000 feet per bined efficiency.
minute on the way.
The “pure” water from the condensed steam Example
still contains valuable energy and for efficient The distribution system for our example has
operation it should be recovered and transport- 10,000 feet [3,050 meters] of high pressure piping
ed back the boiler plant where it is reheated into at 600 psig [120 bar] connected to 4,000 feet [1,220
turned back into steam and recycled in the system meters] of 175 psi [12 bar] sub-system piping.
once again. Figure 5.1 shows a typical steam distribution and
condensate recovery system which will serve for
———————————————————— our example.
In this chapter we will examine how a typi-
Rule of Thumb
cal steam system loses energy and becomes ineffi-
Every 11 deg F [6 deg C] that has to be cient. We will examine the following topics:
added to boiler feed water costs 1% in efficiency.
————————————————————
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1. Trap flash losses
2. Insulation losses
Boilers and their distribution systems have
3. Condensate system losses
a closely interrelated efficiency. The losses in-
volved in distribution systems have a significant 4. External steam leaks
impact on boiler operations and efficiency. For 5. Internal steam leaks
example, if the hot condensate from the recovery
6. Steam trap leakage
system does not return to the boiler plant it must
be replaced with cold makeup water which must 7. Inactive steam piping.
be heated and also receive chemical treatment. ————————————————————
Every Btu wasted in the distribution system must Figure 5.2—major steam system
be replaced by the boiler which wastes about 20% losses which will be covered.
additional energy. This cycle feeds on itself, the
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