CATEGORY: PROCESS CONTROL
CEP - Chemical Engineering Progress, January
2013
Implement
an Effective Loop Tuning Strategy
Norman Ito, Timothy Olsen
Emerson Process Management
Use these loop tuning guidelines to improve process control and enhance product
uniformity
Many undergraduate chemical engineering programs teach the Ziegler-Nichols
tuning methods, developed by John G. Ziegler and Nathaniel B. Nichols in the
1940s. This tuning method has large controller gain and short integral time,
and sometimes creates process oscillations, which are not good for most
chemical engineering applications. As a result, many process control engineers
revert to tune-by-feel techniques.
In
tuning by feel, individual control loops are tuned as fast as possible without
disrupting upstream and downstream control loops. However, by tuning only individual loops, the
overall process performance and the ability to recover from disturbances are
reduced. When a process has been tuned by feel, console operators often need to
put controllers into manual operation to settle the process down after a major
process disturbance.
Automatic process control attenuates disturbances and maintains
control of the process variables to match desired setpoints, and appropriate
tuning enables this capability. This
article describes process control basics, and details a step-by-step process
for control loop tuning.
Free Full Text Source: http://euedocs.emersonprocess.co.uk/groups/public/documents/articles_articlesreprints/cep_loop_tuning_wilson.pdf
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