
CHAPTER 11
Control Systems—Steam and Motor
Boiler Water Level Control.
Modern high pressure, high performance water tube
boilers present a considerable number of problems with regard to the control of
water level. The drums are relatively small in size and water capacity but have
high outputs, whilst the reaction of the steam and water in the drum to changes
in steam demand and hence drum pressure, are complex. A sudden increase in
steam demand reduces the steam pressure in the drum, and to drop the temper-
ature of the water to a saturation temperature matching the new pressure, some
of the water flashes off into steam causing the formatio