Batch control

Batch is a general term given to a diverse set of time dependent control strategies including  

State variable control, such as the opening and closing of a solenoid or the starting and stopping of a motor, including the use of any timing circuits which may be used for alarming in the event the action doesn t achieve its specified results in the allotted time. 

The modification of selected process variables in accordance with a prespecified time-variable profile. Two examples are the changing of the reactor temperature over time to conform with a specified profile or the timed periodic addition of nutrient into the bioreactor. 

Conducting event driven actions such as adding antifoam upon the detection of excess foam or invoking an emergency shut down routine if an exothermic reaction goes beyond controllable limits. 

Performing a sequence of operations in a coordinated manner to produce the desired changes to the contents of a process unit. This would typically include combinations of the above mentioned activities on various sets of equipment associated with the unit. 

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Table 2. Conceptual Levels in a Batch Control Hierarchy...

T. G. Fisher, Batch Control Systems, Instmment Society of America, Research Triangle Park, N.C., 1990. 

General References Fisher, Batch Control Systems Design, Application,... 

An excellent source of reference on the topic of Batch Control systems is the Instrument Society of America s (ISA s) Batch Control Systems Standards SPSS document (ISA SPSS). 

Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response. 

Eisher, T. G. 1990. Batch Control Systems—Design, Application, and Implementation. Instrument Society of America. 

Proportional-plus- integral-plus-derivative Any Large Fast Batch control processes with sudden upsets temperature control... 

Ma, D.L., Chung, S.H. and Braantz, R.D., 1999. Worst-case perfonuance analysis of optimal batch control trajectories. American Institution of Chemical Engineers Journal, 45(7), 1469-1476. 

Guidance on specifications is divided into universal tests/criteria which are considered generally applicable to all new substances/products and specific tests/criteria which may need to be addressed on a case-by-case basis when they have an impact on the quality for batch control. Tests are expected to follow the ICH guideline on analytical validation (Section 13.5.4). Identification of the drug substance is included in the universal category, and such a test must be able discriminate between compounds of closely related structure which are likely to be present. It is acknowledged here that optically active substances may need specific identification testing or performance of a chiral assay in addition to this requirement. 

Activities Carried out Manufacture of active substance Manufacture of finished product Manufacture of intermediate or bulk Q Packaging only Importing Laboratory testing Batch control and batch release Storage and distribution Investigational medicinal products Other ... 

We were able to identify, by early 1987, fourteen batch control packages meeting our criteria sufficiently well to merit detailed investigation. 

Instrument Society of America, 1995, Batch Control Part 1 Models and Terminology , ISA-S88.01. 

Batch-continuous crystallization, 8 95 Batch control system information,... 

Quality System shall provide for control of material and product identification during all stages of production and delivery. Identification is based on applicable drawings, specifications, or other documents. When required or specified, complete traceability of material or product shall be maintained by issuing unique or batch control numbers and/or markings. The identification and trace-ability procedure shall be fully documented to provide objective evidence of compliance with this Code in accordance with this requirement. 

Key operating parameters that may change (or be optimized) throughout a product s development and approval cycle are dissolution sampling time points and dissolution limits or specifications by which the dissolution results should be evaluated. The results generated from the dissolution test need to be evaluated and interpreted based on the intended purpose of the test. If the test is used for batch-to-batch control, the results should be evaluated in regard to the established limits or specification value. If the test is being utilized as a characterization test (i.e., biopharmaceutical evaluations, formulation development studies, etc.) the results are usually evaluated by profile comparisons. 

Area 200 control uses a batch controller. Each reactor is monitored and controlled separately. Level sensors and control valves meter the agent, energetics, or propellant along with sodium hydroxide into the empty reactor vessel. Fluid density is used to monitor and control the caustic concentration in the reactor vessel. 

It may be necessary to retain samples of intermediate products in suiScient quantities, and under appropriate storage conditions, to allow the repetition or confirmation of a batch control. 

Ghosh [2] also lists the requirements for batch process controllers. Batch control methods must include the abilities to ... 

Agitators capable of level 2 will Blend miscible fluids to uniformity, if specific gravity differences are less than 0.1 and if the viscosity of the most viscous is less than 100 times the viscosity of the other Establish complete fluid batch control Produce a flat, but moving fluid-batch surface. 

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