In industrial batch/continuous production environments, production scheduling is concerned with allocating resources such as tanks, reactors and other processing equipment to production tasks. Scheduling determines what product is to be made, how much is to be made and when it is to be made. Detailed scheduling optimizes the production schedule through describe the production process with a heuristic model to find the best way of allocating the available tasks and resources. Detailed scheduling is a centerpiece of production and closely interlinks with production control, order processing, material and energy control and maintenance.
In order to be able to provide all the necessary information for making logic decisions, it is in some cases necessary to implement data transfers that are not supported by the ISA-95 standard for enterprise to plant integration. One example of production parameters that are not included in the standard are release dates and due dates of products. The release date is the exact time from which on a product can be produced. The due date is equally important and refers to the date that the product has to be available, usually due to a customer requested time.
The integration of a scheduling solution for a steel plant using the ISA-95 standard is described. The application shows one way of benefiting from the already existing elements and expanding the B2MML files using the means provided. The resulting input data contains much more information than ISA-95 was originally designed for because the optimization takes place as a separate module on an MOM level. All input/output information must thus be provided through ISA-95. On the other hand, the output file fits completely to the ISA-95 landscape. This case study also shows that many practical applications only need to implement a small part of provided elements and there are always several options to make this happen.
MESA White Paper #33 was produced as part of the MESA/ISA-95 Best Practices Working Group through an international peer review process involving 5 or more subject matter reviewers. This MESA White Paper will also be published in one of two methodology best practices collection, Book 2.0, When Worlds Collide in Manufacturing Operations (Collections published by ISA, 1/1/11).
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