Washington DC 3rd Class Boiler Practice Test

In a three-element feedwater regulator, three signals are used to determine how much feedwater to add. The boiler drum water level is monitored to keep the level at a safe, set point. The amount of steam being drawn off (steam flow) represents the load or demand on the boiler, so it acts as a forward signal to increase feedwater when more steam is produced. The actual feedwater flow (how much water is being fed in) provides feedback to calibrate the response and prevent overreacting to changes in steam flow.

Together, these three measurements let the regulator respond to changing steam demand while maintaining the correct water level. Boiler pressure or draft aren’t part of this three-element loop, as they relate to different control objectives rather than the direct level-maintaining feedwater regulation.