To enable the fixed-length pipe routing features in the 3D model, the piping spec must include pipe with Use Fixed Length selected (true) and a Fixed Length value specified.
AutoCAD Plant 3D 2014 Extension 2 adds a new property: Minimum Cut Length. When routing pipe in the 3D model, the minimum pipe segment length created is the Minimum Cut Length.
To better support Iso drawings, you can set Content Iso Symbol definition to include TYPE=PIPE-FIXED and specify an SKEY that represents the end type.
You can also set these values in the catalog and create or update the piping spec.
Note: Minimum Cut Length applies to all piping (not only to fixed-length). When piping is cut-back while routing, the pipe segment is not cut back shorter than the minimum length.