How do you develop a control philosophy for a process unit?

Control philosophy development: (1) Define control objectives - safety, product quality, throughput, efficiency. (2) Identify key variables - manipulated and controlled. (3) Develop regulatory control scheme - level, flow, pressure, temperature controllers with appropriate pairing. (4) Address interactions - decoupling or proper loop tuning. (5) Define operating modes - startup, normal, turndown, shutdown. (6) Safety interlocks - ESD triggers and responses. (7) Advanced control - cascades, ratio control, feed-forward where beneficial. (8) Document in control narrative. Key principles: close level loops with flow, close pressure with vent/make-up, pair fast variables with slow, and provide adequate rangeability for all operating cases.