Sunday, 22 June 2008

Equipment Procedural Entity

There have been discussions in the S88.01 Update meetings about Equipment Procedural Entiies (EPE's)

This is how I view EPE's -

They are objects such as Phases that can be executed under the command of a Recipe - for example an SOP, or a Production batch, a Batch manager Control or MES Recipe - but which are contained in - and controlled by - the equipment controllers.

The Equipment Controller might be an Operator who runs the equipment manually or if the equipment is automated, the Process Controller - PLC/DCS, Relays or whatever - that is connected to the physical equipment. (Most times it is a mix of the two)

EPE's are part of equipment control.

In Object oriented terms they are like the Methods of Objects
The Equipment that contains the EPE is a Unit or an Equipment module depending whether the Recipe-Equipment Interface is at the Unit or EM level.
Note, the S88 standard says that Control modules cannot have EPE's. But this is no problem - if you must control one CM from the recipe, create an EM to contain it. There is no law against it.

The EPE's can be Phases, Operations or Unit Procedures.

Now, the standard does not say this, but what follows is I think consistent with the models. It is also a configurable aspect of ControlDraw.
Equipment that contains EPE's must also be Acquirable, which mean that the Control Recipe takes control of the Equipment when it needs to carry out some processing in it. And to take control of it means preventing others from controlling it. Which to me implies Acquiring the equipment.

There is a direct correlation between the Equipment Requirements of the Master Recipe and the Equipment that contains EPE's .

That means that the Recipe Equipment Requirement maps to the physical equipment.

This can be one for one in cases where the recipe must use specific equipment or one to many in cases where the Recipe can use different (but similar) equipment.
For example a Recipes' Equipment Requirements might have a Reactor and a Filter but the plant has several Reactors and Filters. The Acquire process involves reserving the equipment for the current batch.

The last draft has a diagram, "Figure 18 – Referencing equipment entities at different levels within a control recipe procedure."

See also
Think of batch standard as design philosophy
Much more to come !

Wednesday, 18 June 2008

S88 Control System Designs

I think that it is a very good idea to use the S88 part 1 models as a framework for a batch (and indeed other) control systems. If you have a reasonable Control System design then it should be possible to use S88.01 Models and Terms to write a fairly precise description of the design.
That does not mean that S88.01 is a design for a control system. And that is clearly stated in the original standard.
Part 5 as it stands appears to be attempting to go into areas (such as a generic model for equipment and control modules) that are explicitly excluded in the introduction to Part 1.
Most worryingly the Part 5 fans are now trying to change Part 1 by introducing their models into Part 1. It is bad idea that would undermine the beauty of Part 1.
Now, Part 5 fans, please understand that I do realise that you may have some very good Control System designs (tho mine may be better) but that is not the point, Part 1 is not at all about designs for Control Systems.
If the objective is have a standard design for re-usable Control System Objects, then it should have a major input from the suppliers just as the development of FieldBus and the like has had.
They are notable by their absense from the Part 5 - where are ABB, Emerson, Yokagawa, Siemens etc. Mostly they are lurking - they are on the mailing lists but rarely take part.

Tuesday, 17 June 2008

Equipment for Making the Tea

The Turks do it another way

But that is for a completely different type of Tea.
So let us look at the Boil Water step in our English Tea Recipe.
Disregarding for the moment that this is probably control in a Common Resource, the typical English Kettle has a switch that once you have put water in it will boil the water and then stop.
The Recipe to make tea hands over to the kettle for that process action.
While the kettle is boiling it is executing the Boil Water part of the Control Recipe for your cup of tea.
Of course you do not Have to have an Electric kettle, you could use a pan on a gas ring, or a camp fire, just for example.

Friday, 13 June 2008

A Batch Recipe

Name : A cup of tea:
Version: Typical English
Equipment Requirements
Process Inputs:
Dried Tea Leaves (optionally in 'Bags')
Energy for Heating
2g of leaves per cup
Pre-heat teapot by using a short flush with nearly boiling water.
Put tea in Hot Teapot, then Add boiling water to a teapot.
Stir (optional).
Wait 3* minutes for tea to brew. (*time is a operational/user choice)
Put Milk in Cup - This can be done while the tea is brewing.
Please note - the milk Must be added to the cup Before the Tea!, (This is a Critical Recipe Parameter).
Pour tea into cup.

Slurp it up

Good things found in Vista:
Windows Key the type the name of the application - :

Wednesday, 11 June 2008

Sequences are not Recipes

I completely disagree with a heck of a lot of what you say part 5 blog.
The latest is
Is that a Sequence or is that a Recipe? The answer is - You say Yes
I say no, in fact I say do not even compare them. To do so undermines the great concept that S88 provides, - separation of Recipes and Equipment.
S88. 01 is not actually about Control, it is about how to describe recipes and the physical equipment they have to run with. The cookbook and the kitchen.
Chop with knife number 42, turn on the power for the cooker, rotate knob 3 to set the temperature on the oven, etc is in the equipment sequence.
Chop the carrots, put in preheated oven is in the recipe.
These are not the same, they interface but are not equivalent.
The formula in a packing machine, just like the temperature of the oven in the recipe and the set point for the mixing tank are local copies of the recipe formula - part of the control recipe and derived from the master recipe.
Your statements on this blog are potentially damaging to the value of S88 Part 1.
Part 1 by the way should be left unchanged, if I had a vote I would vote against the update and for the original.

MS Vista

I make and sell software for Control Engineers to design their systems with. Of course it is Microsoft based, sorry you open source people out there, but MS is so much more productive for me.
I have wondered whether, or even when, it will be feasible to convert ControlDraw to a web served application, like those that Google does. Maybe I could stuff it full of adverts and retire on the revenue, but that is not my intention yet.
My customers, at least those who work sometimes from their new gleaming home PC's are buying Vista machines these days, and I found that some of them could not run CD
So, ControlDraw Ltd bought me a new Laptop with Vista, and in a day the problem was fixed.
However, I have just had 3 black screens in succession, after installing Vista SP1 and Visual Studio 2008. It took a Safe Start then another reboot to get the machine running properly again.
I thought Vista was not supposed to to that. I guess Vista is still Beta- but in reality so is all software. And Standards. They have flaws that get fixed over time. (unlike S88, but that is not fair as S88 is not like that, it does not need fixing)
Vista is nice, but another big flaw is that I cannot get VB6 Service packs to install.
That looks to me like MS forcing up their revenues, I cannot find an excuse for it. I should be able to use my existing development setup, that I have paid them for.
Notwithstanding, I am now playing with the latest and greatest development tools from MS

Friday, 6 June 2008

Recipe Control

I see that Dave has blogged about Recipe Control

"No where that I can find does the ISA88 standard deal with “Recipe Control” as it does with “Equipment Control.” it says. My jaw dropped when I read this so I posted a fairly mocking response, but as usual it takes days before comments on that 'blog' appears if at all.

I think that the post indicates that the most fundamental purpose and meaning of Part 1 is not understood by the poster. Let me explain why I say that.

The entire Original Part 1 is all about Recipes and how to make stuff according to a Recipe.
And keeping the Recipes independent from the equipment and yet being able to run the recipes in the available equipment. The Equipment gets Controlled Yes. The Recipe provides the Set Points and the Procedural Sequence, but the Equipment Does the Control!

Part 1 quite rightly strictly excludes defining how to program either recipes or the control of equipment. Part 1 as it is does a very valuable job of providing a framework in terms of the words that can be used, and models that can provide a structure where those words can be used to describe the required Recipes and the Equipment Control.

Recipe Control is a meaningless term - unless we are talking about how to manage the Recipes themselves. Such as making sure that they are kept safely, version management, ensuring that a Recipe is up to date and approved for use etc.

When thinking about Recipes, it always helps to use the cooking analogy. So what do the cook books say about Controlling a Recipe. Try Searching for Cooking Control. Did that help?

By the way, Dave's 'blog' is not really a blog, but never mind. If you comment on this one it will appear - immediately, please feel free.