Saturday, 29 March 2014

Expert Witness Training: Water Engineering Expertise

I attended one of Prosols Expert Witness Training sessions yesterday, on the Meeting of Expert Witnesses often ordered by the court.

There are a number of such courses offered by various providers. The Expert Witness Institute organised the first couple I went on, which were on writing Expert Witness Reports and  cross examination as an Expert Witness.These three courses covered the most difficult areas of the expert's role, though I discovered in doing them that my natural approach to these things is the correct one.

I am presently finishing the writing of a Part 35 compliant expert report for a UK government agency, and I hope that one of the two cases I have been offering expert opinion on will go to court later in the year so that I can have another opportunity to practice assisting the court in person.

One of the issues we covered yesterday was how to challenge the expertise of the other expert to offer an opinion on the matters under consideration. This is something I think it likely I will have an opportunity to practice in future, when there are so many non-engineers willing to offer advice on engineering matters.

Simply put, expert engineers are Chartered Engineers. Non chartered "engineers" are probably neither experts nor engineers, and Chartered Chemists may be expert chemists, but they are not engineers. If you are looking for an Expert Witness in Water Engineering, you want an expert engineer.

There are two engineering disciplines which understand how water and sewage/ wastewater treatment plants work- Environmental Engineers and Chemical Engineers. Chemical Engineers have the deeper understanding of how processes work, and are consequently traditionally a lot better paid (something I am trying to fix with Nottingham's Environmental Engineers). So a Chartered Chemical Engineer is likely to be far more expensive than the miscellaneous scientists and "engineers" who claim to offer expertise in our area, but if you choose wrongly, the court will be unlikely to allow you to change your "expert" once you have chosen one.

At best you get what you pay for, and Google seems full of people who will write you an "expert" report on anything, including my area of expertise. I guess they are gambling on the fact that 98% of cases never make it to court, so they will never be cross-examined on their partisan and ill-argued reports. Sooner or later I look forward to seeing one of them have to defend their dross to a barrister.

Thursday, 20 March 2014

Real Plant Design

I have a few confidential design jobs on the books at present, and they remind me that the problems of design of real plants are not mathematical in nature ( though we may use maths to help solve them)

All of these projects are development work, developing small integrated process plants which are to be sold as products, which means that they have to meet Van Koolen's test of being as simple and robust as a washing machine.

The problems are however exactly the same as on larger scale plants, (though the lower skill level of the operators makes the design if anything more challenging):

Collaboration with clients and designers from other disciplines uses a lot more of my time than higher mathematics or leading edge science.

Geometry is often a lot more important than calculus.

Cost, safety and robustness are a lot more important than genuine novelty.

Novelty is always constrained by practical considerations.

Process Plant Design and the Use and Abuse of Modelling and Simulation Software

I have a number of process plant design courseworks ready to mark, some for pharmaceutical plants, and some for groundwater treatment plants. I am always looking for new industrial visitors to set my students design challenges, and  have obtained agreement today from an industrial gas plant supplier to provide a design project for a plant including cryogenic distillation next year, which should stretch our second years a bit.

They tell me that they make a lot of use of simulation and modelling programmes to support their design process, as air is essentially the same everywhere, and their plant at smaller scales is made up of well characterised blocks of equipment, for which they have written well characterised blocks of code for Aspen, a simulation package.

It is starting to seem that this marks the dividing line between use and misuse of simulation and modelling programmes. If you have a great deal of applicable data on the exact plant you are designing, and are designing many similar plants, you can go to the effort required to fit a modelling programme to your plant, and writing accurate models of your unit operations. Plant design then becomes a question of linking these blocks into an integrated model, and optimisation of the model can be a valid proxy for optimising the plant.

If you are doing a one-off design, you do not have a great deal of information about the plant which will be built. Rather than using a validated model, you will be using the straight-out-of-the-box generic data and models, and optimisation of this unvalidated model makes no sense. The errors in the model are very likely to be greater than the resolution of the optimisation procedure.

Plant operators are the ones holding the information necessary to validate and tune modelling software. The contracting companies who design the majority of process plants do not have this information, and consequently make less use of modelling. This is presumably why the most commonly used modelling software is written to support the oil and gas companies who are best placed to put in the data, time and effort needed to validate modelling software.