MIL-HDBK-1003/7
e)
Parallel metering system with oxygen trim.
CO trim w/coal.
f) Steam flow/air flow metering system. Boilers should have oxygen
trim in order to optimize fuel usage. CO trim should be considered for larger boiler
installations as an adjunct to oxygen trim for increased efficiency, especially for coal
firing.
Maintenance and Calibration. Maintenance and calibration is a necessity
11.1.6
regardless of the type of control equipment being used. Pneumatic instrumentation will
require more maintenance because of its usage of air that contains dirt, moisture, oil,
and other contaminants than its electronic counterparts. Also, pneumatic
instrumentation will require more frequent calibration checks because of its inherent
mechanical linkage design versus solid state electronic units.
Steam power plant controls are shown in MIL-HDBK-
11.2
Steam Power Plant Controls.
1003/6, Section 6 and Table 13.
Combustion Control. Combustion control comprises a series of devices on a
11.2.1
boiler developed to satisfy steam demands automatically and economically by controlling
furnace combustion rates through adjustments of the burning components while maintaining
a constant set point (such as a fixed but adjustable pressure or temperature) and an
optimum (adjustable) ratio of fuel to air.
a)
For the metering type (proportioning plus reset plus rate action),
see Figure 37.
b)
Combustion safeguard. See Military Specification MIL-B-18796,
Burner, Single, Oil, Gas, And Gas/Oil Combination, and MIL-B-18797, Burners, Oil,
Mechanical-Draft, Automatic.
c) Refer to the ASME Boiler and Pressure Vessel Code Section VII
subsection C6 for minimum basic instruments required for proper, safe, efficient
operation.
d)
Refer to Tables 13 and 15 in MIL-HDBK-1003/6, Section 6.
e)
See Tables 22, 23, and 24 for typical lists of instruments.
Steam Temperature Control. Steam temperature control shall be as listed in
11.2.2
MIL-HDBK-1003/6, Section 6, Table 13. Critical temperatures should be recorded and also
alarmed. An automatic fuel-trip device is required for steam temperature out of normal
range. See Table 23 for temperature sensing devices.
Feedwater control shall be as listed in MIL-
11.2.3
Feedwater Control.
134
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