DISCUSSION

DISCUSSION

This process control laboratory is about to run open and closed loop process. In this report Liquid Flow Process (FIC 31) is being used. By using the response curve from the loop analysis, Response Rate (RR), Time delay (Td) and Time constant (Tc) are calculated by using Reformulated Tangent Method. After that,Tuning Rules by Chien, Hrones & Reswick (CHR). PI calculation is chosen because of our value of RR is small.

At the beginning, the initial value set point of MV is 35%. After sometime, when MV value is 40% the value PV (%) is 6.15. Response Rate at this time is 27.15 s-1 . Dead time (Td) is 0.0150s. PB, I and Kc values are calculated using the formula and the value obtained are 68.01% , 0.06s and 1.4703 respectively. Critical time (Tc) is 0.0526s.

Next, by performed the load disturbance test, the value of MV is increased from 47.3 to 57.3%, and observes the response curve as well as wait until the response curve become stable. Summary for all control loop and all test result in table 5, 6 and 7. Next, by performed the load disturbance test, the value was set back to the initial value which is 35%. the value is set to the highest value which is 50%.

After set up and running the process control system in Auto mode, enter the value of controller gain (Kc) and integral time (I) that has been calculated manually using Chien, Hrones & Reswick (CHR) into the system control. During the process, the response curve is observed and analyzed. Whenever the response curve is oscillating and active, the process is tuned until the response curve is stable and process is closed to the set point. Tuning is the process of setting control loop gains or other control variables to achieve optimum value and stable performance. The value of controller gain, Kc and integral time, I are the control variables that was considered to achieve optimum controller setting. In this experiment, there is no exact value for the process to achieve an optimum performance. Under steady state condition, when the graph line of set point and process (PV) variable is equal then it is considered as optimum performance. In tuning process, whenever the response curve are oscillate very fast, the value of the controller gain, Kc have to be reduce by divide the original value by 2 or 4 and increase the integral time, I value by multiply by 2 or 4 or with other value. But in this report based on the experiment the process is already stable right after the values are inserted. When the MV is 50% the value obtained the RR is 27.36s-1 and the Td, PB and I values are 0.015s, 68.54% and 0.06s respectively. The value of Kc obtained is. 1.459.