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The How of Layout

By: , Posted on: March 28, 2017

Layout designers must satisfy several key criteria in their designs:

  • Efficient, reliable and safe plant operation
  • Safe and convenient access for maintenance of process equipment by complete or partial removal or in situ repair
  • Acceptable levels of hazard and nuisance to the public and environment
  • Adequate levels of security to protect against the risk of crime, vandalism and, potentially, terrorism
  • Safe and efficient construction
  • Effective, economical and ergonomic use of space
  • Compliance with local planning regulations regarding aesthetics
  • Compliance with Environment Agency (or equivalent) requirements
  • Compliance with any other relevant codes and standards.

The supply of services to the plant and access to the periphery of the plant for maintenance, construction and emergency services is affected by the location and layout of the site.

The initial layout is usually based upon the process flow sequence shown on the process flow diagram (PFD), with the unit operations arranged in process order. Physically adjacent vessels and equipment are separated by distances that are sufficient to permit safe operation and maintenance without wasting space.

The layout of some plants may follow the process flow sequence closely through to the final stages but, in practice, there are features that commonly require the layout sequence to differ from this default case. These include: process requirements; economics; operability; control requirements; ease of maintenance, construction, commissioning, future expansion and extension, ease of escape and firefighting; operator safety; hazard containment; environmental impact; product protection; insurance and observation requirements; wind direction; equipment stacking; and the location of any off-site utilities.

Changes to the initial PFD-based layout may result in extra pipework or transportation costs, and increases in site or building area. Such changes must be economically justifiable. The cost, safety and robustness implications of each design decision should be borne in mind by the designer.

A detailed knowledge of the characteristics of process materials may be needed to ascertain the requirements of hazard containment, whose evaluation must in any case be carried out by suitably experienced process engineers. In some sectors, process engineers may not directly undertake design activities needing less process chemistry knowledge and training. However, all layout designers require the ability to identify and use relevant statutory and in-house regulations, design standards and codes of practice, and to appreciate the needs of operation, maintenance and construction. Most importantly, perhaps, they also need to be able to apply engineering experience and common sense.

Thus, this work may be carried out by designers and draftspersons supervised by process engineers or architects experienced in layout design. Exactly how this is done (and who it is done by) varies from sector to sector.

Nowadays, there are several types of players in the design process, most notably client/sponsor/operating company; consultant; process engineering procurement and construction (EPC) company; mechanical and electrical EPC company and process design houses.

As well as the various types of organizations involved in design, there are several disciplines within these organizations, most notably Process; Mechanical; Piping; Electrical; Instrument; Software; Civil and Structural engineering and Architects. The teams responsible for Installation, commissioning, and validation, Procurement and inspection should also be increasingly involved as design progresses.

Design work proceeds to some extent in parallel within the various disciplines and design offices. It is one of the tasks of the project manager to coordinate these activities, assisted by the layout designer and process engineer.

Good document control and model sharing between disciplines and organizations is vital, to avoid situations in which one discipline is working to a layout which has been already changed by another.

Liaison outside the design team is also important. The regulatory authorities responsible for planning; health and safety; and pollution as well as the emergency services; transport authorities and press.

In-house quality assurance staff, as well as insurers, equipment suppliers, raw material suppliers and product end users, utility suppliers, waste disposal facility suppliers, construction companies, commissioning team and future operating and maintenance personnel will all have opinions on the design. These opinions have to be considered, though with so many opinions to consider, a strong lead designer is essential.

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

About the book

process plant layoutThe second edition of Process Plant Layout explains the methodologies used by professional designers to layout process equipment and pipework, plots, plants, sites, and their corresponding environmental features in a safe, economical way. It is supported with tables of separation distances, rules of thumb, and codes of practice and standards. The book includes more than seventy-five case studies on what can go wrong when layout is not properly considered. Sean Moran has thoroughly rewritten and re-illustrated this book to reflect advances in technology and best practices, for example, changes in how designers balance layout density with cost, operability, and safety considerations

 

About the author

sean moranProfessor Sean 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.

Sean’s latest books are available to order on the Elsevier Store. Use discount code STC317 at checkout and save up to 30% on your very own copy!

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