18-04-2012, 03:58 PM
AUTOMATIC PROCESS CONTROL
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GOAL:
Maintaining process variables (temperatures, pressures, flows, compositions, levels) at a desired operating value.
Processes are dynamic in nature, and changes are always occurring. The important variables those related to safety, product quality, and production rates will not achieve design conditions.
Manual process control
Based on this comparison, decide what to do to correct for any deviation. The steam valve can be manipulated to correct for the deviation.
Disadvantages of manual process control
The operator should look at the temperature frequently to take corrective action whenever it deviates its desired value.
Different operators would make different decisions as to how to move the steam valve, resulting in inconsistent operation.
This corrective procedure would require a large number of operators.
Why control is important?
Safety: Prevent injury to plant personnel, protect the environment by preventing emission and minimizing waste and prevent damage to the process equipment.
Maintain plant production rate at minimum cost
So, we can say that the reasons for automation of process plants are to provide safety and at same time maintain desired product quality, high plant throughput, and reduce demand on human labor.
SUMMARY
Present two types of control strategies: Feedforward control or feedback control, we also discussed their advantages and disadvantages,