Thursday, 14 February 2008

Save the Batch

Or how to be an S88 Purist and how it will improve your controls, be it batch, discrete or continuous.
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.
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.
I will try to extend this in time, but for the present take a look at "Is a storage tank a Unit?" which shows how to run a control recipe in a storage tank just like any other batch control recipe .

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