Final answer:
The Pressuretrol is the unit in a steam boiler system that controls the burner, turning it on and off to maintain the required pressure of the steam.
Step-by-step explanation:
Within the context of a steam boiler system, it is the Pressuretrol that regulates the burner. This unit is responsible for switching the burner on and off in order to maintain the required steam pressure. Systems like the pressurized water reactor use mechanisms such as pressuretrol to ensure that criticality is reached but not exceeded and that safety measures like steam escape valves are in place. As for the other options, a safety valve also plays a pivotal role by releasing excess pressure when necessary, a fusible plug melts under extreme heat to allow steam escape, and a poppet valve manages the flow of liquids.
Learn more about Pressurtrol