A very useful too, for us in plant 3D is Centre of gravity (COG) on our piping,
If the pipe is a nice straight and equal section, this normally isn’t an issue
But the more complex spool sections can give people a headache.

To use this functionality,
We need to set the items weights or else Plant will not be able to give an accurate COG
Open the Spec editor and go to the Catalog Editor tab,
Find the object you want, in this case a pipe,
Set the Weight unit and Linear weight,
Then select the Sizes tab.

Select the size of the pipe,
As this is a pipe, we set the Linear Weight, so in this case it is kg per meter,
If it was an item like an elbow, you would use the Weight field.
Click Save to to Catalog.

Jump to the Spec editor tab,
Right click any component and select Check for updates from Catalogs,

An update should be found, select Update specs parts to match catalog parts.
Once updated, Save and head back to Plant 3D.

Right click the Pipe Specs and select Check for Spec Updates.

Select Update pipe specs,
Check all updated parts boxes and select the Update Parts.

If you go to the Analysis Tab,
Turn on Live COG,
Then select a pipe run,
You may get the following issue,
This is because something in the selection has not had its weight defined in this case the elbows.

If you go back to the spec and add the missing values,
It should then display correctly.