Produces steam without the use of a fired boiler. Heated thermal fluid from a thermal fluid heater circulates through the tubes of the steam generator, heating water surrounding the tubes and converting it into steam. This has significant advantages over a boiler with a fire tube. Unlike a boiler, the heated tubes in the steam generator can never get hotter than the thermal fluid flowing through them. This eliminates the explosion hazards commonly associated with boilers. Moreover, it eliminates the need for a boiler tender, who must be present whenever a boiler is in operation.