S88 Working Draft 5 Version 4

This seems to be an incredibly complicated document with no explanation of the reasons for it, or the rationale behind the various concepts that it tries to present.
Why do Automation objects need to contain Functional Manager or a Resource Manager?
A PID controller (a good example of an automation object) is something that has been in existence for around about a century, and it never needed such things, what is the reasoning behind making it so complicated?

Some internet travelling experiences

I know this blog has been silent for too long, I have been travelling, in fact I still am, this comes from New Zealand, where the connection is excellent. I thought I would share some internet travelling experiences:
The Motel in Brisbane that advertises Free internet.
On arrival the person in reception asks for your laptop and then types in the password, taking care to prevent the password being saved. When you close your laptop lid and it shuts down or hibernates the password is required again when you restart.
Reception closes at 8pm (I immediately cancelled my reservation and moved out when I found this, fortunately before 8pm)
The Hotel in Sydney that charges $30 (AU) per day
The hotel that has a third party that provides WIFI. The signal is strong, but the performance is unusable, the third party, (Jimojo.com), said that there was no problem with their systems. Ha !
And finally using the internet with a mobile phone connected to a laptop via Bluetooth. I can tell you that at least with VodafoneAustralia it works well. But can you believe £10 per Megabyte. That means it can cost about £1000 per hour. At the same time you can get 5Gbyte per month for about £20 if you have a local account. Legalised robbery

The Next WBF topic

I see that the next WBF is dedicated to “Expanding the horizons of manufacturing”.
That leaves plenty of scope in North Carolina I guess. I was going to suggest "Manufacturing models for a Sustainable future", maybe for the the next one. Or perhaps it fits in with expanding out horizons, so I hope those who are currently working on their presentations for the North Carolina conference will consider the issues in their papers.
I know that we are in a global economic crisis, for maybe a few years. Economic models have long process lags. But the process I am talking about when I refer to the future is much slower moving. And it is one of the areas where those involved in manufacturing can help, from minimising energy consumption to using sustainable resources. Even a control module, such as an agitator or pump can be controlled in ways that save energy, higher up the levels more can be done. I am sure that the forum can find many people with great things to say on the topic.

WBF Barcelona

The Barcelona WBF was good, it was well organised and of course in a lovely city and even the weather was fine. There were people from 23 countries there. I met many people that I have known for years from previous conferences and working with some of them and also made new friends.

And I was presented with the Guido Carlo-Stella Award, which I am very pleased about, thank you all. I remember Guido from the early years of the EBF.

Much of the conference was oriented toward the S95 domain and Manufacturing Excecution Systems. It is challenging to absorb so much information- 25 papers - in 2 days, so I am reviewing the papers again in my own time, and refreshing my knowledge of S95.

PLC is 40 years old!

The PLC is 40 years old, time flies, I first saw one when they were maybe 5. In fact I learned much of my Batch control by programming PLC's. That is where control happens, in the controllers, surprisingly enough. 

While I may have complained that the WBF does not have enough about Control I had not looked though all the papers presented at this years USA Conference. (It is worth joining the WBF for this alone by the way, some are gems) and found one on implementing recipes in a PLC, by Igor Steiner, Janez Tancek, Marko Svetina at INEA d.o.o.

I hope they won’t mind me quoting a bit from their paper

This is about PC based recipe managers versus writing your own in a PLC

Pros:

High level of abstraction for complexity management

High flexibility&reusability

Rich functionality

Cons:

Unsatisfactory reliability of the PC platform

Poor adjustment to small and medium projects

Unsatisfactory time behaviour of the PC platform

Too low expressive power of phase behaviour mode

An interesting comparison, I generally agree. The Too low expressive power point is one that I think might be based on an over optimistic view of what a Recipe Phase has to do, for me there is very little it has to do apart from starting and monitoring the execution of an equipment phase, via a phase logic interface. I don’t even believe the ****ing states (such as Pausing!) should exist in the PLI, why does a recipe care about that?

The programming of the equipment phase itself of course can be done in the process controller, PLC in this case, and there you can do what you want using the power of PLC instruction sets, which have high expressive power.

The paper also describes the Concept of Tabular Recipes on a PLC, nothing new, to my knowledge something similar was done in Wigan in the mid 80’s using Siemens S5 PLC’s, but worthy all the same. There is by the way a popular misconception that S88.01 revolutionised batch control, I think that makes the point that it did not. It helped to specify it though, I agree with that, and it raised understanding of the issues.

PS - in fact Tabular recipes have existed in ControlDraw for many years 

WBF Barcelona

I case you are wondering, I shall indeed be going to this event, I am looking forward to it.

See you there I hope.

Alarms and Equipment States

How many reports on hazardous incidents have you read about where the alarms presented to the operators were excessive and the resulting confusion contributed to the incident.

I was reminded by this article

Why Is Safety so HARD?

The problem has been known and understood for decades, and now we all know that alarms should be suppressed when they are not relevant, and that when they are they should be prioritised.

But engineering a solution is time consuming and expensive.

The solution has to be specified, reviewed and approved, and maintained as operating experience is gained and the solution is modified, via an approved change process of course.

Typically these are described by text, cause and effect matrices and logic diagrams.  

Mostly the cause and effect matrices describe the responses to potential hazardous events, such as process upsets. The matrices do not often cover the alarms, although some do mention them typically in notes. Some control system actually support Cause and Effect matrix based design, and can translate them into control logic. For example Siemens has one

These are much more constrained than the typical excel version that people produce.

 

Using a state model provides a highly efficient way to define the enabling of alarms. The safety system, as a complete entity is defined in terms of possible states, a method that vastly reduces the number of states that have to be considered.

Then each possible alarm can be considered for it relevance in each state, producing an Alarm State Matrix.