PLCbatch
Batch Process Control Tool on a Standard PLC Equipment
PLCbatch complies with the requirements of the international standard ISA S88.01 standard, and on the other hand it is simple to use and therefore useful in processes where expensive and complex tools are not suitable. The guidance in the development of the PLCbatch solution was, beside the simplicity, also the elimination of the critical unreliable componentitem from the continuous real-time implementation of batch process control – PC computer with its basic function of a batch server. Its functions are transferred to the PLC controller, which is today the most standard and reliable automation element in automation industry. By transferring control functions from PC computer to industrial controller, the reliability of the entire control system has been significantly increased by transferring control functions from the computer to an industry controller. PLC itself becomes batch execution engine while still taking care of phase logic, and basic control of the process. The need for real-time communication loops and the need for an industrial PC is eliminated. The need for redundancy is drastically reduced. The new concept is simple, cost effective, reliable and understandable, yet sufficiently powerful for most cases of batch process control.
In the PLCbatch solution, the PC computer is in the PLCbatch solution used only in non-critical parts of control, that is in designing and arranging recipes, arranging the equipment and control over the implementation of management. These are all non-critical and indirect levels of control, which do not cause the termination of the production procedure in case of equipment failure.
Scheme of a typical PLCbatch system configuration:
An example of batch tracking on operator panel:
Characteristics of the complete batch control system or recipe level structure:
- Compliance with the S88.01 standard,
- Recipe management (creation, arranging, archiving in XML format) on PC computer,
- Batch management (creation and issuing -work orders) on PC computer,
- Execution of recipes is implemented on the PLC platform, without a PC computer in the control loop,
- Supervision of the execution can be performed via a PC computer (with the supervision still being subject to the consequences of unreliable PLC platform) or via an industrial operator panel (thus the entire control including supervision is performed on the PLC platform).
Characteristics of recipe management or execution and recipe behaviour:
- Simple understandable tabular presentation of recipes,
- Two-level recipe structure (phase level and procedure level of units or operations),
- Concurrent execution of more recipes (control of more lines), the only limitation being the capacity of the selected PLC,
- Support of parallel (AND) and selective (OR) recipe branches,
- Checking the consistency between a recipe and process physical model,
- Overview of exceptional situation (failure or holding causes) and start-up conditions.
Features of execution of individual phases:
- Phases are presented as state machines in compliance with the S88.01 standard,
- Division of phase actions to entry, loop and exit actions of individual states and transition actions,
- The tool fully executes state machines of phases, which means that the application program is composed of a great number of elementary sequences.
PLCbatch modules:
- Recipe editor,
- Batch server,
- Batch View - operator interface with functions:
- Batch list view,
- Procedure as table view,
- Phase Control,
- Phase logic interface.
Effects:
- Increased reliability,
- Simple implementation,
- Implementation in compliance with the S88.01 standard,
- Lower material consumption,
- Better traceability,
- Favourable price.
For more in-depth presentation of the innovative approach of PLCbatch solution:
A Batch Process Control Tool on the PLC platform Presented at the World Batch Forum, North American Conference, Philadelphia, PA, USA 24 - 26 March 2008
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