DIAGNOSTIC DATA-BASED SAFETY AND AVAILABILITY ENHANCEMENTS FOR AN ALTERNATIVE OF FEEDFORWARD CONTROL USING FOUNDATION FIELDBUS

To enhance plant safety and production availability in case of transmitter failures for an alternative of Foundation Fieldbus (FF)-based feedforward control, this article proposes a practical technique for configuring control strategy using function block diagram concept. The proposed configuration technique is based on fault diagnostic data automatically accessed from FF transmitters to take actions for operating the studied FF-based control loop that utilizes a Bias/Gain (BG) function block to build feedforward summing function outside of a proportional-integral-derivative (PID) function block. The minor 'Uncertain' problem can be treated as severe 'Bad' problem to increase the safety of the control loop. On the other hand, the 'Uncertain' status can be configured to be treated as 'Good' status to improve the availability of the control loop. Six options for configuring function blocks to operate the temperature control performed at the DeltaV host system are described as a case study to demonstrate the workability of the proposed technique. Experimental results of the alternate feedforward control loop configured with different parameter options confirm that the diagnostic data provided by the transmitters used are very useful for implementing either the interested control loop with increased safety or the interested control loop with increased availability. Therefore, the user can strike a balance between safety and availability for the FF-based feedforward control utilizing BG function block.