Minnesota's high-pressure-piping code is contained in Minnesota Rules Chapter 5230 and Minnesota Statutes Chapter 326B (PDF).
Renew a high-pressure-piping license online
E-Licensing surcharge is in effect (PDF)
Verify a personal or contractor license in DLI's searchable database.
The High-Pressure-Piping Laws and Rules (Chapter 5230 plus selected statutes) are available at Minnesota's Bookstore.