What control will shut down a steam boiler if the pressure rises above the set operational limit?

The high limit switch is the control designed to shut down a steam boiler when the pressure exceeds a preset operational limit. This device protects the boiler from potential damage that can occur due to excessive pressure. When the pressure reached inside the boiler surpasses the set limit, the high limit switch automatically interrupts the power supply to the burner, stopping the combustion process and preventing further pressure increase.

Understanding that the high limit switch serves a specific safety function helps clarify its importance in boiler operation. It acts proactively, ensuring the boiler remains within safe operational parameters and avoids potentially hazardous conditions. Other devices like the automatic pressure relief valve and safety valve are intended for different functions, such as releasing excess pressure to ensure safe operating conditions, but they do not directly shut down the burner in response to high pressure. The manual reset pressuretrol requires human intervention to reset, making it less effective in automatically responding to an unsafe condition compared to the high limit switch.