Integrating Process Response

Know the difference between a self-regulating process response and an integrating process response... 

Understand the procedures and methods for tuning controllers for self-regulating and integrating process responses while the controllers are running in automatic output mode... 

The process dynamics of a few process variables can be characterized as an integrating process response. One example is the response of the liquid level in the bottom of a distillation column when liquid is being pumped out with a centrifugal pump and the liquid flow rate is restricted by an automatic valve after the pump. The column base liquid level may be steady with an initial automatic valve position, and opening the valve to a new position will increase the liquid flow rate. The difference between the two flow rates will be integrated over time as seen by the response in liquid level going down. Eventually, the column base liquid level will go to zero... 

The level controllers for the reflux drum and the column base level for a distillation column are examples of integrating process response. If a level controller is put in manual output mode and the valve position for the liquid flow out of a reflux drum is increased, the level in the drum will integrate the difference, that is, sum the difference over time, and eventually empty the drum. Similarly, decreasing the valve position will allow the drum to fill and eventually overflow. Consequently, the Robbins method of pattern recognition for tuning of level controllers uses a different set of rules as follows ... 

This chapter described the concept of a self-regulating process response and an integrating process response. Several methods were described for tuning a control loop while the controller is in automatic output mode. These include the trial-and-error method, the Zlegler-Nlchols ultimate gain method, and the Robbins pattern recognition methods. 

Another example of an integrating process response is the storage of an inert gas in a pressure vessel. The inert gas can accumulate or can be depleted from a storage tank as indicated by the gas pressure in the vessel. 

An integrating process response, for example, the level in a reflux drum or distillation column base, will eventually overflow or run empty in an open-loop step test without further manual intervention. One example of an open-loop step test... 

Write the time response solutions to the integrating process in (3-14) when the input is (a) a unit step and (b) an impulse. How are they different from the solutions to a self-regulating... 

The best results in evaluating coating control units are achieved with ITAE. There are overshoots, but the reaction is fast and the ripple time short. Controller setting conditions have been worked up for all integral evaluation criteria just mentioned so as to minimize the related deviations. With a manual input as well as vi/ith experimental determination of the process response coefficients, the ideal PID coefficients for the ITAE evaluation can easily be calculated from equations 6.13,6.14 and 6.15 ... 

Control of integrating processes with time delay and inverse response (IPTD8t.IV)... 

W.L. Luyben, Identification and tuning of integrating processes with deadtime and inverse response, Ind. Eng. Chem. Res. 42 (2003) 3030-3035. 

When the analytical laboratory is not responsible for sampling, the quality management system often does not even take these weak links in the analytical process into account. Furthermore, if sample preparation (extraction, cleanup, etc.) has not been carried out carefully, even the most advanced, quality-controlled analytical instruments and sophisticated computer techniques cannot prevent the results of the analysis from being called into question. Finally, unless the interpretation and evaluation of results are underpinned by solid statistical data, the significance of these results is unclear, which in turn greatly undermines their merit. We therefore believe that quality control and quality assurance should involve all the steps of chemical analysis as an integral process, of which the validation of the analytical methods is merely one step, albeit an important one. In laboratory practice, quality criteria should address the rationality of the sampling plan, validation of methods, instruments and laboratory procedures, the reliability of identifications, the accuracy and precision of measured concentrations, and the comparability of laboratory results with relevant information produced earlier or elsewhere. 

We showed that this dynamic behavior originates, in effect, from the large discrepancies between the flow rates of the different material streams in the process (captured by the recycle and purge numbers), thereby establishing a clear and causal connection between the steady-state design and the dynamic response of an integrated process. 

The integrator is responsible for collecting the chickens on the day of kill and transporting them to their licensed processing plant. When the number of birds is relatively low the farmer may have to catch or assist in catching them on the day of slaughter. 

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