In many specialty chemical and pharmaceutical batch processes, you’ll find classic cascade and split-range control strategies used on vessel jacket heating and cooling.
I caught up with Emerson’s Mark Coughran on a recent visit that he and Guillermo Bravo had taken to a plastics manufacturing facility. They were having issues with the jacket temperature control that used this classic cascade & split-range control strategy.
Here is a partial piping & instrumentation drawing (P&ID) showing this control strategy:
They were experiencing large temperature overshoots and undershoots, and even in some batches, interruption to the recipe setpoint. Here was temperature trend that Mark and Guillermo found upon their visit (details omitted to protect confidentiality):
These overshoot and undershoot conditions were affecting the performance of the manufacturing process and overall batch length.
Over the course of their 3 days working with the plant staff, they performed these actions:
Through this consultative approach understanding the root causes and impacts, Mark and Guillermo were able to vastly improve overall control performance. One of the key changes that helped reduce the overshoots and undershoots was to implement a feedforward control strategy in the temperature controller.
The as-left batches had practically no overshoot and undershoot, and generally more consistent behavior, at the main reaction temperature of 74. Even better, this improved temperature control helped to reduce batch cycle times by 10%.
They also provided recommendations on ways to improve the hardware and software, so the plant can reduce the overshoot when approaching 57. While this specific success was performed on a DeltaV DCS controlling the process, the Entech Toolkit can be used with any control system. The Emerson Control Performance Improvement & Optimization consultants have experience working with many different control systems running heating & cooling control strategies across many industries and applications.
Learn more by visiting the Lifecycle Services – Performance section on Emerson.com. You can also connect and interact with other variability management and control performance experts in the Services group in the Emerson Exchange 365 community.
Update: Added Guillermo’s photo and a note about the role feedforward control played in this solution.
The post Improving Jacket Heating and Cooling Temperature Control appeared first on the Emerson Automation Experts blog.
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