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S88 - Phases, Units and Equipment Modules

What is S88 for? The standard says

"Make recipe development straightforward enough to be accomplished without the services of a control systems engineer"

This paper presents some observations about how many actual systems have been structured and suggests why  many suppliers have mostly failed to achieve that objective. And it proposes better ways of structuring them to improve the ease of recipe development.
And it is not just about making recipe development easier for the end user, but also about improving the whole life - cycle, reducing the time taken to develop each batch application.

 

Lets look a typical phases, as found in many systems. The S88 model shows these as Either acting on a Unit or on an Equipment Module

"Process action: Minor processing activities that are combined to make up a process operation."

In many systems, entire phases are often dedicated to 

Starting or stopping an Agitator.
Jacket temperature control.
Prompting an operator. (Message phase)
Should these really be phases?

No - they do not Perform a Process action ie - “run a minor process activity”

Now, taking an agitator as an example, suppose it is not made as a Equipment module, but as a Control Module containing in a Unit
Is is easy to design an Agitator Control module that can by itself r

respond to changes in the level in the vessel,
slow down and stop as level drops
run energy saving algorithms (cycling on and off)

In the ‘classic' or Equipment Module Centric design, Equipment modules run phases
Seems to be the normal practise 
But when the EM’s are split up the operations must address each equipment module typically in parallel.