Water level cascade control: article / Siti Nor Mashita Mahadi

Liquid level controlling is useful and important phenomena in industrial, domestic and many other applications. The main uses are in chemical and power plants; where a slight deviation can lead to a major accidents and huge losses in revenue. To overcome this issue, it is best to implement cascade control system in the plant. With the cascade control strategy, an improved strategy can be achieved since any change in the liquid level is immediately detected by the level measuring element and level control will takes corrective action. In this paper, comparison between single and double loop control was compared and examined to prove that double loop is far more efficient than single loop. The effect of changing the proportional (P) value in both inner and outer loop was examined to study the effect on the process. Consequently, the most optimum value of proportional (P), integral (I), and derivative (D) in tuning process will also be identified and the effect of detuning the value was observed. The effects of this values is examined and observed on Level Flow Process Control Training System (Model: WLF 922). As the system consists of two different loops, method in which primary and secondary loop are tune simultaneously by using an open-loop test. The PID value from both open loop test is obtained by using Ziegler-Nichols tuning rules. Finally, explanation of the observed behavior based on PID values and general guidelines to assist in the procedure of controller retuning are given.