Hello, I am in the process of converting a project’s units from Imperial Inches to Metric.
I know the workflow for using Revit to make all the necessary conversions in each pipe fitting family, the whole project in general, and am very experienced in REVIT MEP.
I am interested in using Dynamo to make easier the process of changing a list of nominal pipe sizes - for example, converting a nominal 2" pipe gives me exactly 50.8 mm. To change that specific size I have to create a new segment size, and enter the nominal as “50mm” then copy over the exact measurements for ID, OD etc. I would like to use Dynamo to create a script that can take my SIZE CATALOG for existing Pipe Segments, and convert the exact mm conversion in the table to the nominal mm size without re-creating the pipe segments.
Example image from a Jing screenshot:
Problem is, while I have been able to find and adjust many of the parameters in the pipe segments with Dynamo, I cannot find where the SIZE CATALOG is buried in Revit.
If anyone can point me to a node that could read from or write sizes to the SIZE CATALOG in a given pipe segment I would appreciate it. It’s possible I will have to create a custom node - that sounds like a fun can of worms.
Just to clarify, do you want to duplicate your US imperial pipe segments and create equivalent US Metric pipe segments? If that is the case, I recently went through the same process without using Dynamo. Create the new pipe segment with a Metric name and use the associated Imperial segment as the basis for your sizes. Then, if you click on a pipe size and click “New Size”, it copies the pipe OD and ID dimensions. You then only have to type in the new size. With your example, click on the 2" pipe size, click New Size, and type 50 for the new size. No need to retype the ID and OD values. Repeat this process for each size and then go back and delete the imperial sizes. It didn’t take me very long to do and I have quite a few pipe types. Changing the pipe size units to mm helps during this process.
I also considered trying to use Dynamo to assist with this task, but found I could manually create the pipe types faster than I could figure out a Dynamo script (if it’s even possible). Also, this isn’t something I’m going to do on a regular basis. I know I didn’t answer your question, but at least offered a way to make your task easier to accomplish.
Thanks, I didn’t know about the specific behaviour when selecting one of the existing sizes before clicking “new size.” In spite of Dynamo appearing awesome, I always appreciate a non-Dynamo answer when there is one 
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