TABLE OF CONTENTS As discussed in Chapter 1, the ISA SP88 standard classifies the process based on the number of products it manufactures and physical connections as follows.
In a process with single-path structure, the batch passes sequentially in a predefined path from one unit to another unit.
In a process with multi-path structure, there may be several batches active at a time and the equipment may be of different physical characteristics.
In a process with network structure, the sequence of the units may be pre-assigned, determined prior to execution of the batch or even during the execution of the batch. In network structure process, an appropriate path is determined at the time of execution, depending on constraints like recipe requirements and equipment capabilities. Control of network process is complex due to the need for allocation of equipment and the arbitration of requests for the equipment.
For a batch process, ISA S88 describes the following models:
Physical model: To explain physical assets of the enterprise.
Process model: For sub-division of a batch process.
Procedural control model: For sub-division of procedural elements of batch process.
Procedural equipment mapping model: For defining links between the above three models in order to achieve the batch process functionality.
Recipe-type model: To define the recipe types and relation between different types of recipes.
Control activity model: To deal with functional activities of a batch system.
In this chapter we will learn...
