Saturday, 6 September 2008

More on ISA S.5.06 Functional Requirements

I have spent some time delving into this standard, and the examples it provides.
Further than that, I have now created a ControlDraw model that captures basically everything that the standard shows. This is for me the best way of understanding a process.

One thing that amused me about the batch reactor example is that it has nowhere to send the batch it makes apart from down the drain! It calls dumping the product down the drain the Dump Phase, part of the Transfer operation, I suppose dump is appropriate, but Transfer? Maybe I missed something - here is the P&ID

S5.6 has this thing called a Sequence matrix. This is a condensed overview of the example process, but I suspect that it really would not be workable when scaled up to a real, and more complex process. Furthermore it conflates too much into too little, and if you are trying to do in in Excel demands lots of formatting. ( And the example manages to avoid the most complex issue, the transfer.)

So my model does not use that method - it is optional, you can also use Sequence charts - and instead uses those, in the form of SFC's and PFC's
Maybe a complex query could generate the matrix from the combination of the sequences and the equipment - it is possible but it would be a huge table compared to the example sequence matrix. Even without adding a real transfer!

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