What is the role of the pressure governor in a fire service pump?

The role of the pressure governor in a fire service pump is to control engine speed when it detects excess pressure. This function is crucial in maintaining optimal performance and safety during firefighting operations. When a fire pump is operating, the pressure within the pump and discharge lines can vary due to flow changes. The pressure governor monitors these variations and adjusts the engine speed accordingly. If it senses that the pressure is exceeding set limits, it will decrease the engine speed to reduce the pressure. This automatic adjustment helps prevent damage to equipment and ensures a consistent flow of water under various operational conditions.

In contrast, the other options do not accurately describe the function of the pressure governor. Raising the pressure of the water line is not its primary purpose; the pressure governor acts to maintain a balance rather than increase pressure. Additionally, it does not regulate water temperature or directly monitor flow rates—these functions are served by other components and systems within fire apparatus. Thus, the pressure governor's main responsibility is to protect the integrity of the firefighting system by modulating the engine speed based on pressure readings.