Sugar boiling plant - with discontinuous control and automatic change-over between modes

摘要

The consistency of the boiler contents is measured during the boiling process and up to a given threshold level e.g. 10-20% crystal content, esp. 15%, the feed control valves for the water and syrup feeds are controlled by a regulator which uses as input control parameter the super-saturation of the contents but above that threshold uses the measured consistency itself. A single change-over relay with three sets of contacts is used to switch the control parameter input between the consistency sensor and between a quotient generator using the same sensor's signal after conversion and the measured temp. in the boiler; it also switches the regulating input between the measured level and a desired level for the boiler and the output between the two above control valves. Loss of production due to difficulty of accurate control with a manual system is prevented.