PIPE (PIPE-FLO Data) is a format used for piping designs created with the PIPE-FLO software. This software has some ability to import other file types; you can run Python scripts to process various sorts of data such as CSV files, and DXF image files can be embedded in version 12 and above.
It appears the files have
ESI PIPE as an ASCII string starting at the second byte of the file.
- Tutorial Complete v12- US Units.pipe, found in the knowledge base where imports of data are discussed