Using a Scada Package for Pan Floor Process Control

Priorto the 1991/92 season,Noodsberg usedacustomdesigned PC based system for pan boiling control. This system was abandoned in favour of a new supervisory control and data acquisition (SCADA) package, calledTurbolink, mainlybecause of a lackofavailablesupportfor theoldsystem. Thenewpackage has provedto be extremelypowerful and its scopeof application has been extended to the provision of an overall pan floor management facility. The package is used to control the boiling ofall rawhousepansthrough thegeneration ofsetpointsforstand aloneconductivity controllers. It also provides, amongstothers, a loggingandgraphicstrending facilityfor vacuum, temperature, conductivityandlevelofallpans. Throughtheuseofaproduction report facility, it also automatically logs the timeof each boiling and providesstatistical information on these. Historical Overview In 1987 Noodsberg installed a customdesignedautomatic pan boiling system based on the Sugar Milling Research Institute (SMRI) automatic pan controller (Keen, 1986). The system, usingdedicated SABUS hardware, controlledall nine rawhouse batch pans and in addition, provided an historical data logging capability for pan level, conductivity and vacuum. The basis of controlwasthegeneration ofa remotesetpointtriggered by using 16predetermined level points. A valuable feature of the system wasits standalonecapabilitywiththe remote conductivity signal driving individual panel mounted controllers so that in the event of any PC failure the pan boiler still maintained local automatic control via the controllers. The SABUS system more than justified its original R20 000 investment by providing enhancedpan control for A-, Band Cpans until hardware failureand lackof servicesupportduringthe 1991/92 seasons prompted management to consider alternative systems. The factory staff already had experience with a cost effective SCADA package using a 286 IBM compatiblePC for mill data loggingand with relativeease the R12 000 Turbolink mini package with 128 analogue inputs was substituted for the SABUS system using the existing 286 IBM compatible Pc. The successof the minipackageprompted mill staff in 1992to upgrade the package to a midi Turbolink version with 256 analogueinputsand256digitalinputsandat thesametimethePCwas upgraded toa 386IBMcompatible model. Aschematic representationof how the system is set up is given in Figure I.