I am integrating reviewer comments into my radical rewrite of Mecklenburgh's Process Plant Layout, and soliciting new comments via social media.

It is very apparent from this conversation that layout aspects of plant design have undergone what biologists call speciation. There are now a number of species of plant design, with very limited interaction, or even awareness of each other (and don't even get me started on the pointless, fruitless attempts by mathematicians in academia to treat plant layout as if it were a mathematical problem)
Those responsible for plant layout are usually process engineers, piping engineers or process architects. We might view the approaches of these disciplines as the parents of the various species of plant layout methodologies, but they have cross-bred and evolved into a number of hybrid approaches / designers in the environment of various industries. Older designers can still be following one of the pure-bred parent approaches, which still exist alongside the newer ones, as they still work (unlike those academic approaches I mentioned).

For example, how layout is done in the Oil and Gas industry, (where piping engineers are key to plant layout) now differs radically from how they are done in the pharmaceutical industry, where process architects are taking a lead far more often. How it is done (and who does it)  on small plant designs differs radically from how it is done on larger ones.
Even the language used to describe key documents and parts of the plant differs in complex ways.  The meaning of "plot", "site", "plot plan" and "general arrangement drawing" not only differs between designers, but they differ in ways which are not simple substitutions of terminology.
What's the difference between a pipe rack, pipe bridge, pipe track and pipe bent? To me, pipe -rack and -track are synonyms, pipe bridges are -racks which go at height over roads, and pipe bents are the steelwork which holds up a pipe rack. People however use these terms to mean all kinds of things.

This seems to be why when I ask people to critique the draft of the book, I often get quite strong responses (such as "NO!!!!!!!") to the approach and terminology followed by other species of layout designer (the term I am using in the book to encompass the process engineers, piping engineers and process architects who lay out plant).

To avoid becoming hopelessly confused, it is necessary that I read these responses in the context of the age, industry experience and original discipline of the reviewer, and I have laid out many plants.

How I cut through the confusion to offer readers a number of easy to follow approaches, whilst capturing the speciation which has taken place is my key writing challenge at present.