The process of defining the various modules in an S88 based application is critical - if done well the resulting application should make recipes easy to develop and the systems should be easy to program.
The generally accepted process of modularising starts with the Piping and Instrument Diagram and involves identifying the Units, Equipment modules, Common Resources and Control modules.
Many of the Control Modules can be directly associated with instruments on the P&ID, but it is also possible that you will find higher level Control Modules, see Control Module Types
Often when analysing a process people start by dividing the process into Units and Equipment modules, but without thinking where are the Batches?
It greatly helps if you start by looking for the batches. And Everything can have a batch, even storage tanks.
Once everything has a batch, you can use S88 terms through all your application without confusing the recipe with the equipment.
An important thing about the batches in a plant is that they are not often one for one. For example a pallette of chocolate bars, a tanker full of milk, a delivery of hazel nuts can all be seen as batches, but one tanker full of milk for example may be used to make dozens of batches of milkshake, which in turn makes hundreds of bottles.
Drawing a Batch relationship diagram is a good way to crystallise your ideas.
Once that is done you can find the units and the recipes, and decompose them.
Then you can match the procedures to your elemental basic control. Which you can get straight from the equipment for example a P&ID.
Adding higher levels level control modules in Basic Control can makes this far easier.
Step by Step
Find Control Modules on the P&ID
Identify Units and Common Resources
Identify Equipment modules
Decide on the Phases that the Units and Equipment modules can run.
Units Must have phases, for example Receive, Empty, Mix and Heat etc.
If you find equipment modules that do not really need phases, because they can simply do what the unit needs then fine. Do not make them for the sake of it. Examples of this include Agitators and Temperature Controls.
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