Much of my professional practice nowadays is as an expert witness in commercial disputes where there have been problems with process plants, mostly originating in the design process, though poor commissioning and operation can make even a well-designed plant work poorly.

I have been working as an expert witness since the mid-nineties. Though I can discuss the details of very few of my engagements due to confidentiality agreements, I think that it is safe to pass on a few lessons on how not to design process plants which this work has taught me.

The key lesson is to do with competence. Often the process design of even the largest plant comes down to the competence of a single individual. Theoretically, no plants get built based upon the work of one individual, as QA systems like the ISO9000 series require checking of calcs, design reviews and so on.

In practice, the real design of plants always happens under resource pressure, and even if suitably qualified engineers are available to check calcs, they will not check every box in the spreadsheet. I usually find errors when I come to do the same check without time pressure, and with a brief to mind mistakes. The original checker might have had a brief to just get the thing signed off.

Design reviews tend not to double up on disciplines. The process design will get checked against the requirement of other disciplines in a design review, rather than verified by a second process designer. Management oversight of the process will necessarily be at a superficial level.

It therefore really matters who does your process design. Some bad choices I have encountered in multi-million pound jobs are: experienced process designers from another sector, green grads with no previous process design experience, sandwich students, and most popular of all in the plants which don’t work- no one. They simply decided to dispense with process design entirely.

At least the experienced process designer from another sector will apply the tools of the chemical engineer. They will do a mass balance, process and hydraulic calculations, and produce PFDs, P+IDs, layout drawings and so on. They will have some ability to anticipate the needs of other disciplines, and know how to communicate with them clearly. They will have the professional’s dislike of novelty, but they will be hampered by a lack of knowledge of how things are normally done, and why: they lack know-how. This has made the difference between a working plant and one which is beyond economic repair on a number of occasions in my experience.

The undergrads and green grads without expert mentors do not apply the professional’s tools, instead they naively apply what they were taught at university. They love novelty, rather than avoiding it, and specify things based on sales pitches and lab scale work. They attempt to design process control systems from scratch using what is called “HAZOP” in academia, despite having no understanding of the control characteristics and failure modes of equipment. They lack attention to detail, especially in respect to balancing the cost, safety and robustness implications of their choices. They lack knowledge of how to communicate with other disciplines, and the implications of their communications. They assume that someone is going to make sure that the plant really works, especially if they are working for a big blue-chip company.

These green grads are sometime worse than my last category, the jobs where there is no process designer at all. These are informative in telling us what chemical engineers actually do, and which bits is the most important. Of greatest important is undoubtedly the mass balance. In its absence, process plants which are designed without input from chemical engineers simply do not work as an integrated whole, and are missing important things which a rigorous mass balance would have identified. The second most import thing is also to do with producing an integrated system, but from a software rather than a hardware point of view. Process control systems without chemical engineering input do not in my experience produce a cost effective, safe and robust plant. In fact the plants I have seen of this type do not really work at all.

The issue of working and not working is another area where there are commonly problems. If you buy a plant without specifying a performance test against set criteria before handover, you are making an investment in some lawyer’s pension fund. All too often I ask a client I the plant which is mot working very worked, and when we get right down to it, they simply don’t know, because they accepted it without a trial. Here’s some free legal advice – don’t be that guy.

So what is competence? The courts have some ideas on that in respect of offering credible expert witnesses. Competence in the opinion of the courts is acquired through relevant professional experience. Despite the fact that I have taught many other things in an academic setting, I almost exclusively work as an expert witness in the field of the design and commissioning of water and effluent treatment plants.

I have personally designed dozens of such plants, and carried out troubleshooting exercises on hundreds, which makes me familiar with the normal professional methodology which so many of these cases are to do with from a legal point of view. Knowledge of such methodology is as the cases I have offered above show, absolutely crucial to producing a working process plant. Real engineers innovate as little as possible.

Read more posts from Sean Moran, The Voice of Chemical Engineering

About the author

Professor Moran is a Chartered Chemical Engineer with over twenty years’ experience in process design, commissioning and troubleshooting and is regarded as the ‘voice of chemical engineering’. He started his career with international process engineering contractors and worked worldwide on water treatment projects before setting up his own consultancy in 1996, specializing in process and hydraulic design, commissioning and troubleshooting of industrial effluent and water treatment plants.

Whilst Associate Professor at the University of Nottingham, he co-ordinated the design teaching program for chemical engineering students. Professor Moran’s university work focused on increasing industrial relevance in teaching, with a particular emphasis on process design, safety and employability.

Connect with Sean on LinkedIn here, check out his Facebook page here and stay up-to-date on his thoughts, research and practice at his personal blog here.

Connect with Sean on LinkedIn here, check out his Facebook page here and stay up-to-date on his thoughts, research and practice at his personal blog here.

An Applied Guide to Process and Plant Design

Process Plant Layout

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