Safety performance lower control limit

The purpose of constructing the control chart is to graphically identify trends in data that indicate areas that must be addressed. When using control charts, safety managers will want to note data that is a trend or data that is out of control. Data that consistently falls between the upper and lower control limits, or data that is in control, may indicate that the control limits need to be recalculated with the more current data, thus tightening the control limits and thereby further improving the expected performance levels. 

Real Time Optimization. This module receives the values of the variables of the plant, performs reconciliation on these values. This node has a steady state (mathematical, physically based) model of the plant. An optimization is made using that model every hour or so. The optimization results are sent to the lower level, the supervisory control. These results are the new set points of the controlled variables. The best operating point of the plant (which means a set of set points values) is calculated in each optimization. The optimization takes into account constraints on the variables (limited change in manipulated variables, safety, quality, etc. constraints in controlled variables). The node uses as well a historian module with past data of the plant. 

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