Flow feed-forward control is the most utilized and underutilized advanced regulatory control technique. Proper implementation involves the use of ratio control and cascade control. Processes can be started up and moved quickly to new operating points by achieving a new flow ratio. Temperature and composition loops have a particular ratio for any given setpoint, whereas level and pressure loops have a ratio typically independent of setpoint. The ratio is found by simply dividing flows from an up to date Process Flow Diagram (PFD).
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