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The Why, What, How and Who of Plant Layout
The Why Of Plant Layout
A study by Kidam and Hurme (2012) showed that 79% of process plant accidents involved a design error, and the most common type of design error leading to accidents was poor layout, as shown in their illustration above. A good layout is a safe layout.
The What Of Plant Layout
The discipline of layout design is concerned with the spatial arrangement of process equipment and its interconnections, such as piping. Good layout practice achieves a balance between the requirements of safety, economics, the protection of the public and the environment, construction, maintenance, operation, space for future expansion and process needs. It will also consider weather conditions, country specific legislation and regulations, as well as aesthetics and public perception.
The How and Who Of Plant Layout
There are three main approaches to layout design. These are the Chemical Engineer’s approach, the Piping Engineer’s approach, and the Process Architect’s approach. The table below illustrates where such approaches are likely to be followed, and the characteristics of the approaches.
Each of these disciplines may lead the layout design process, or provide the primary model used for the process. Other disciplines will be involved, but one of these three disciplines will tend to set the approach to layout design. Since not all the possible lead disciplines are engineers, I have used the term “layout designer” throughout the book as the designation of the engineer or architect responsible for layout design.
Chemical or Process engineers will always be involved in layout, as they are required in all cases to size the unit operations (process equipment) and, to some extent, to set out their mutual interrelationships in space. They may do little more than this, they may lead the process, or they may do all of it themselves on smaller plants in certain sectors.
Piping engineers are often used where there is a lot of complicated and expensive pipework, for example in the traditional bulk chemical or oil and gas industries.
Architects are often used where there are significant numbers of buildings, or where the plant must be integrated within a building. In recent years, architects have become increasingly responsible for on the layout of indoor process plants as part of the building design.
Whilst there is a certain amount of disagreement about where to draw the imaginary lines between its stages, plant design is nominally a five-stage process:
- Conceptual: before design sanction
- FEED: after design sanction
- Detailed: before project sanction
- “For Construction”: after project sanction
- “Post Construction”: after project handover
These five stages are used almost universally because the adverse consequences of not having accurate cost and hazard assessments will increase considerably at each successive project stage.
The preliminary stages of layout involve conception, evaluation, and modification, with the last two being repeated until a satisfactory solution is achieved. Detailed layout involves developing the minutiae of the preliminary layout. Process and project experience remains the best basis for layout conception and modification, even though computers and their software applications have come a long way since the first edition of this book.
The designer assigned to detailed layout is also involved with project planning, especially so since the introduction of computers for planning control.
Hazard assessment of prospective layout designs is now very much a multi-disciplinary partnership including layout designers and chemical engineers, amongst others. The training, skills and experience of the chemical engineer are applied to the plant hazard identification, assessment and mitigation techniques which have become an essential part of preliminary layout.
In my new book, I explain the how of plant layout in detail. My next post will be about how we split the task of plant layout into nested areas of equipment, plot and site layout. Until then I’m delighted to offer you a free chapter from this new book – Enjoy!
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.
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