TM 5-810-15
allows a hot restart which bypasses the purge,
and swell of the boiler drum level during load
ignitors and warm burners and allows the intro-
changes. Without the steam flow feed-forward sig-
duction of solid fuel provided certain conditions are
nal, load changes will momentarily cause the drum
met. Figure 9-12 shows sequential logic for burner
level to change in a direction opposite to the load
control.
change. The feed-forward signal provides the
b. Feedwater flow and drum level control.
correct initial response of the feedwater valve.
(1) Two element control. Two element feed-
(2) Three element control. Three element
water control systems as shown in figure 9-13(a)
feedwater control as shown in figure 9-13(b) uses
are characterized by the use of steam flow as a
feedwater flow in addition to steam flow to im-
feed-forward signal to reduce the effect of shrink
prove drum level control. In this system feedwater
9-14
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