Friday, 22 November 2013

Now Booking for 2014

We had another enquiry for some real engineering work this week, another confidential design development job. With all of the work on the books at the moment, we will have to start this in the new year.

I have two expert witness instructions, and three proper engineering jobs on the go now. I'm delivering a couple of training courses in the Middle East at the end of the year, and going to China on University business.

I've also got to get my first book chapter in in January, so it's a busy time.Better get on with it...

Friday, 8 November 2013

Systematic Process Plant Design: state of the literature

As part of preparation for writing my plant design book, I've been reading previous attempts to set out a process plant design methodology for beginners- "Total Design" was just one of many.

Here are my comments on a few more:

Billy Vaughn Coen: "Discussion of the Method" - deep, dense and philosophical, but he does know what design is about - his koan is "all is heuristic". Worth reading.

William D Baasel: "Preliminary Chemical Engineering Plant Design" - written by an academic who did a placement in industry, who came to understand that process design is really plant design, and the importance of what is glossed over in academia. Pity it's so old, but still worth reading.

Backhurst and Harker: "Process Plant Design" - its heart is in the right place, as it understands that what engineers do differs from what uni teaches them, but the authors' academic background makes them emphasise a few areas which they themselves describe as arbitrarily chosen rather than system level design. Don't bother with it - too old, and partial.

William L Luyben: "Principles and Case Studies of Simultaneous Design" - "simultaneous design" considers both steady state economics and dynamic controllability aspects of the process, reminding me of the bar in the Blues Brothers which has both kinds of music. Design for controllability is strongly emphasised in this approach, supported by computer modelling.

The problem is that in achieving his stated aim of producing something smaller and less encyclopaedic than Perry's, he has chosen only two elements. These are without a doubt important partial design elements, but optimising only two variables will not produce an optimal solution- this is process design, not plant design, partial rather than total design, and substitutes modelling for design.

Sandler and Luckiewicz: "Practical Process Engineering, a Working Approach to Plant Design" - Old, but an academic and a practitioner get together get together to try to remedy the shortcomings of academic engineering courses. Has  great deal to say about drawing, and practical hydraulics, but very sketchy and partial indeed when it comes to unit op design - "vessels" covers everything from reactors to storage tanks. Has useful stuff about trace heating lagging and electrical power and motors. Though partial and old, it has useful stuff that none of the others cover. I'm going to expand upon and update some of this unique content in my book.

Peters, Timmerhaus and West: " Plant Design and Economics for Chemical Engineers" - As the title suggest, has a lot to say about economics - also has stuff on technical report writing and delivery. A textbook on partial design for undergraduate teaching written by academics.

Wells and Rose: " The Art of Chemical Process Design"- great title, but unfortunately written by an academic and a software company rep. who think that design starts in the lab and proceeds via simulation and modelling. At least recognises the iterative nature of design, but there is no art here. This looks to be the precursor to the misguided recent books by academics on "Process Design/ Intensification/ Synthesis" which I shall not mention further.

Van Koolen: "Design of Simple and Robust Process Plants" - Simplicity and robustness are indeed  heuristics in plant design, and has some useful summaries of the implications of ten approaches to process or process plant design. Quantifies complexity, which is an interesting and potentially fruitful approach, but then loses itself in combinations of partial approaches, and academia's pointless attempts to substitute modelling and simulation for design. Worth a cautious read.

Pahl and Beitz: "Engineering Design  A Systematic Approach" - Once again, a general text captures the essence of  design in a way that so many chemical engineering texts do not. The Google books review says that " No other book in English provides so detailed and thorough an approach to engineering and design methodology", a claim I am quite willing to believe.

It includes quite a bit of stuff on systematic techniques to supposedly enhance creativity (which I'm not that convinced about) but I'd rather emphasise something which is genuinely a useful aspect of design than things which are not.

The book suggests both explicitly and implicitly that German design teaching is far more closely aligned with professional practice than in the English-speaking world. If true, might this to be to do with the high status of the engineer in Germany? Definitely worth a read, though it's a bit old.

Thursday, 7 November 2013

Total Process Plant Design


 Pugh Elements of the PDS.jpg



















I recently read a book on product design which drew conclusions which I think apply equally to process plant design - Pugh's "Total Design".

He calls the "design" taught in universities "partial design", resulting from the necessary breaking down of a complex and holistic discipline into things which can be taught in an academic setting by non-practitioners.

He talks of the need to contextualise this necessary simplification as just a small part of the real-world total design activity, and to spell out that what is being taught is not really design itself.

The greatest problems with this approach occur when we mistake the bricks for the building - many universities unfortunately teach process design as if processes do not happen in process plants.

This may be elaborated in academia into approaches which ignore all of the real difficulties of total design in favour of an attempt to make design a sort of applied maths in which one or two elements of partial design are combined, to make what they mistakenly think is an integrated model.

In such approaches, the three most important measures of a design's quality (its cost, safety and robustness) are glossed over, in favour of optimisation of a small number of parameters in a greatly simplified model of just part of the plant.

Process plant design is an art, whose practitioners use science and maths, models and simulations, drawings and spreadsheets only to support their professional judgement. It cannot be supplanted by these things, as people are smarter than computers (and probably always will be).

Our imagination, mental imagery, intuition, analogies and metaphors, ability to negotiate and communicate with others, knowledge of custom and practice and of past disasters, personalities and experience are what designers bring to the table.

If more people in academia understood the total nature of design they would see the futility of attempts to replace skilled professional designers with technicians who punch numbers into computers. Any problem a computer can solve isn't really a problem at all - the problems of real-world design lie elsewhere.

In a related issue, on the latest TCE letters page, an article in the previous issue by a vendor of  modelling software which made claims for their software's abilities to co-optimise two unit operations comes in for incredulous criticism.

Setting aside the issue of whether it is worth modelling so precisely something which cannot be built precisely like the model, (because no real world artefact ever is) - If it is questionable whether we can optimise a simple system of a reactor and associated separation process together, it is ridiculous to think we can model a whole process well enough to substitute modelling for design.

Creating a dynamic integrated system level model of a whole process is exactly what process plant designers get paid to do, and they do it in their heads.

The research programme "towards zero prototyping" which inspires and funds that software vendor is a pipe dream. Designers are necessarily people, and any model which runs on a computer falls far short of a reliable description of the real world.

The letter to the TCE pointed out that extensive pilot plant work generated the data which was fed into the modelling software. As the pilot plant work was essential and the software was entirely optional, no progress towards zero prototyping seems to have been made.

Engineering deals with problems which it will almost certainly always be far quicker to ask an engineer to solve than to program a computer to, even if we had the data (which we can never have on a plant which hasn't yet been built), a computer smarter than a person (which we will probably never have), and a programme which codes real engineering knowledge, instead of a simplified mathematical model with no input from professional designers.

I wonder how doctors would feel if scientists and mathematicians suggested that they could produce an expert system which would exceed their competence without consulting any doctors?

This is a classic academic purist's mistake: The psychologist claims that sociology is just applied psychology, the biologist says that psychology is just applied biology, the chemist that biology is just chemistry with legs, the physicist that chemistry is just applied physics, and the mathematician that physics is just applied maths. Emergent properties are irrelevant to the theorist, but in practice they are everything.

To paraphrase XKCD: Engineering is to maths as sex is to masturbation.

Sunday, 3 November 2013

Expert Witness Water Engineering Cross Examination Training

I attended a Cross-examination for Expert Witnesses course on Friday last week with Paul Garlick QC. Great course, which confirmed that I'm unusually good at this already, but there's always more to learn.

Mr Garlick's course gave me an understanding of the strategy and structure behind the different stages of examination of evidence which will make it easier for me to prepare in depth for the two court cases which I have provisionally booked in the medium term.