Beginners at process plant design tend to see the Health Safety and Environmental (HSE) features of a design as something to be sprinkled over the design after it is finished. This is not however the way that professionals treat it.

“Why is HSE the number one concern? Process engineering (especially water process engineering) saves far more lives than the best medical practitioners ever will, but we can do harm on an industrial scale as well. The worst doctor who ever lived might have killed a few hundred people over a long period of time. Bad engineering could kill tens of thousands of people in a day.

The most pressing argument for the prime importance of safety issues is the more or less universal ethical one that people should not die or be injured so that we can make money. The argument for avoidance of environmental degradation is weaker.

Many societies are willing to put up with a degree of environmental degradation in order to industrialize and develop, just as we did. The IChemE metrics reflect the engineer’s view on this, which is a fair bit more rational than the views of some environmental pressure groups and anti-capitalist protesters.

Engineers make decisions on the basis of more or less formal cost benefit analyses. We know that as we try to move toward perfect safety and sustainability, each incremental improvement becomes progressively more expensive.

This fact is accommodated by UK and European law by the terms “as low as reasonably practicable” (ALARP) and the even uglier acronym SFAIRP (so far as is reasonably practicable), which define the required standards of safety. These terms set a limit on how far we have to go. We are not required to make plants any safer if the cost of an incremental increase in safety is grossly disproportionate to the benefit gained.

So society tells us at least how safe they would like our plants to be through legislation. There may, however, be conceivable situations in which our interpretation of our moral obligations as professional engineers requires us to set a higher standard.

In the UK and Europe in general, there is legislation which requires higher levels of scrutiny of Health, Safety and Environmental aspects of a design under specified circumstances. For UK designers, the Environment Agency’s “netregs” website and the HSE’s are very good places to start looking at the requirement s in more detail. The most important aspects for process plant designers are as follows:

Control of Major Accident Hazards (COMAH) legislation requires that businesses holding more than threshold quantities of named dangerous substances “Take all necessary measures to prevent major accidents involving dangerous substances…Limit the consequences to people and the environment of any major accidents which do occur”. There are tiers within the legislation which impose higher duties on companies holding greater quantities of these materials. Plant designers need to consider whether their proposed plant will be covered by this legislation at the earliest stages.

Control of Substances Hazardous to Health (COSHH) legislation requires risk assessment and control of hazards associated with all chemicals used in a business which have potentially hazardous properties. Consideration of the properties of chemicals used as feedstock, intermediates and products is a basic part of plant design. Inherently safe design requires us to consider these issues at the earliest stage.

There is a lot of similar legislation worldwide, and I would recommend the US Center for Chemical Process Safety’s publications intended to assist process plant designers in addressing safety issues

Plants which are more safe or sustainable than society requires are unlikely to be built in the normal run of things. I have seen a few cases where this has been done for marketing purposes by companies with enough spare cash not to worry too much about the costs, but mostly plants are built to make stuff in a cost effective, safe and robust manner.”

Read more from Sean on SciTech Connect

An Applied Guide to Process and Plant Design is available for purchase on the Elsevier Store.

Use discount code “STC215” at checkout and save up to 30% on your very own copy!

About the Author

Professor Moran is a Chartered Chemical Engineer with over twenty years’ experience in process design, commissioning and troubleshooting. 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.

In his role as Associate Professor at the University of Nottingham, he co-ordinates the design teaching program for chemical engineering students. Professor Moran’s university work focuses 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.