Control of Water Level in Marine Boilers during Rapid Changes of Load

Abstract

Conditions in a boiler and steam range during manoeuvring are analysed in order to identify the factors affecting boiler water level, making reference to the Y.E.A.D.1† naval boiler whose behaviour was closely observed during recent shore trials. It is shown that a boiler steaming alone responds to control actions and load changes quite differently from a boiler steaming in parallel with others. A simple theory is developed and used to establish the characteristics ideally required of a feed regulator, and this leads to the conception of a regulator incorporating an unusual type of steam flow element. Comparative estimates of the performance of this regulator and others of conventional design, applied to the Y.E.A.D.1 boiler, indicate that the proposed modification would be very beneficial, but that a conventional two-element regulator is likely to give a poorer performance than simpler types dependent upon water level only. It also appears that feed regulation is easiest when the boiler is steaming in the region of half load. Common design and commissioning procedures are criticized and gaps in knowledge pointed out.