The terms "show boiler" and "historical boiler" are often interchangeable and mean a boiler that is used only for display and demonstration purposes.
In recognition of the historical significance of show boilers in maintaining a working reminder of Minnesota's agricultural, transportation and lumber industries, show boilers and engines are considered to be historical artifacts.
Requirements for piping of historical boilers
The minimum requirements for all traction engines, historical boilers and stationary show boilers:
Boiler proper piping
All piping under pressure shall be seamless and schedule 80. Recommended piping: SA-53 Grade A or B, SA-106 Grades A, B, or C.
All replacement fittings and valves must be steam rated for the appropriate pressure. Note: Ball valves may not be used for main steam shut-off, blow-down or blow-off.
Galvanized piping is not allowed on any steam, feed water, condensate return, or blow-off piping.
Blow-down valves must be of the slow opening type, and the blow-down line must be plugged or capped during the time the boiler is operating on display.
Piping at the point of entry to the boiler must be fitted with a cross to allow inspection of piping. Examples: feedwater, gauge glass, pressure gauge, etc.
Boiler external piping on stationary boilers
On all stationary boilers, all new steam, feed water, condensate and blow-off piping after the first stop valve must be installed by a contractor with the appropriate permit in accordance with the High Pressure Piping Code 5230.0250 – 5230.1060.