MIL-HDBK-1003/7
5.1.5
Selection of Cycle Steam Conditions
Balanced Costs and Economy. For a new or isolated plant, the choice of
5.1.5.1
initial steam conditions should be a balance between enhanced operating economy at
higher pressures and temperatures, and generally lower first costs and less difficult
operation at lower pressures and temperatures.
Realistic projections of future fuel costs may tend to justify higher pressures and
temperatures, but such factors as lower availability, higher maintenance costs, more
difficult operation, and more elaborate water treatment shall also be considered.
Extension of Existing Plant. Where a new steam power plant is to be installed
5.1.5.2
near an existing steam power or steam generation plant, careful consideration shall be
given to extending or paralleling the existing initial steam generating conditions. If
existing steam generators are simply not usable in the new plant cycle, it may be
appropriate to retire them or to retain them for emergency or standby service only. If
boilers are retained for standby service only, steps shall be taken in the project
design for protection against internal corrosion.
Special Considerations. Where the special circumstances of the establishment
5.1.5.3
to be served are significant factors in power cycle selection, the following
considerations may apply:
a) Electrical Isolation. Where the proposed plant is not to be
interconnected with any local electric utility service, the selection of a simpler,
lower pressure plant may be indicated for easier operation and better reliability.
b) Geographic Isolation. Plants to be installed at great distances from
sources of spare parts, maintenance services, and operating supplies may require special
consideration of simplified cycles, redundant capacity and equipment, and highest
practical reliability. Special maintenance tools and facilities may be required, the
cost of which would be affected by the basic cycle design.
c) Weather Conditions. Plants to be installed under extreme weather
conditions require special consideration of weather protection, reliability, and
redundancy. Heat rejection requires special design consideration in either very hot or
very cold weather conditions. For arctic weather conditions, circulating hot water for
the heat distribution medium has many advantages over steam, and the use of an
antifreeze solution in lieu of pure water as a distribution medium should receive
consideration.
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