Pennsylvania Statutes Title 53 P.S. Municipal and Quasi-Municipal Corporations § 25311. License required;  exception

It shall be unlawful for any person or persons to have charge of or to operate a steam-boiler or steam-engine over ten-horsepower, in cities of the second and third class of this Commonwealth, except locomotive boilers, used in transportation, and steam-engines and steam-boilers, carrying less than fifteen pounds pressure per square inch, unless said person or persons are upwards of eighteen years of age, and holds a license, as hereinafter provided for;  and it shall be unlawful for any owner or owners, user or users, of any steam-boiler or steam-engine over ten-horsepower, other than those excepted above, to operate or cause to be operated a steam-boiler or steam-engine without a duly licensed engineer.