Improving the Control of Process Flows

This presentation will introduce an unusual flow control algorithm that out-performs the PID algorithm when used for flow control.  The algorithm was formulated as the result of an intensive study that was conducted on many sets of instantaneous flow measurements, from flows either on set-point flow control using the PID algorithm or on “manual”.  The study revealed some unexpected characteristics of turbulent flow.

Use of this algorithm on each of four (4) hypochlorinators gave control of the mass flows of gaseous propylene (125,000 #/day) to each of the towers to within ¼% of set-point on a continuous basis (24/7).  This precision was proven by both oxidation potential (OP) cells and gas chromatographs analyzing for propylene in the vents of the hypochlorinators.  The ¼% precision was achieved with regular off-the-shelf control valves and positioners.  The algorithm is simple.  Its best feature is that it requires no factors and no tuning.