Q&A – CAD Layers and Productivity


CAD Layers

Is there some type of standard CAD layering for process piping.  I can find standards for electrical and architectural but nothing for piping.  Do you know where I can find them if they exist?

This question has come up many, many times over the years.  In the 70’s, 80’s and 90’s when the available layers started at 16 and grew to many hundreds (depending on the system) people tried to standardize all the layers.  It was just unsolvable problem.  There were too many systems, too many different companies and too many “I’m in charge” CAD Coordinators.   I think at the present time each company tries to have a standard but now the Client tends to come in with their own system and imposes it on to the project.

My solution has always been to establish a “Project” layering standard (with multiple discipline compatibility and Client approval) and then publish it to all pipers on that project.  This is only one of the items I normally published in a document I call a “PDI Book” (Piping Design Instructions).

CAD Productivity, Manual, 2D & 3D

Your question is a hard one to answer. There are too many variables. These include the years of experience of both persons, the type of drawing to be produced, the type of CAD system that is available, the potential for and the type of any changes plus the possible need for any downstream activities.

That being said, if you have two people with the same years and type of experience. and you sit them in separate rooms and assign them to make the same type of drawing with the understanding that there would be no changes then I think it would take about the same amount of time.

The time savings and productive benefit of CAD comes into play when changes are required.

You could also have a time savings for downstream activities such as automated MTO if you had smart symbols in CAD. If you don’t have smart symbols for your CAD and must populate each and every symbol with data so you can do MTO then I don’t think it would be a savings. This would also be prone to a high degree of error.

All that being said I have been frustrated on jobs where I was the supervisor and I assigned a designer to produce a Plot Plan for a process plant proposal. This person had twenty years of experience and was (allegedly) CAD proficient. This was a job that I know I could have done manually in less than a week. More than three weeks later the CAD version was still not done.

The bottom line here I think is that we in the business have a lot of “tools” but we have not learned when to use which “tool”.

Take the roofer, he/she has a hammer and he/she has a pneumatic nail gun. He/she seems to be smart enough to be able to choose when to use the hammer and when to use the nail gun.


This text is an extract from questions gathered from numerous queries of anonymous people in the Piping Engineering and Design profession. The answers or discussion of the topics were provided by James O. Pennock.