A two-element boiler feedwater regulator is controlled by which two signals?

A two-element boiler feedwater regulator is controlled by which two signals?

• A. Steam Flow and Drum Water Level
• B. Steam Flow and Boiler Pressure
• C. Drum Water Level and Feedwater Temperature
• D. Boiler Pressure and Water Level

Answer: (A)

The two-element boiler feedwater regulator uses two process signals that directly govern how much water to add: the rate of steam being produced (steam load) and the water level in the steam drum. Steam flow tells the system how much water must be supplied to replace what’s turned into steam, so the regulator increases feedwater when steam demand rises. Drum water level provides feedback on the actual water inventory; it keeps the level within safe limits by adjusting feedwater up or down to counteract level drift.

This pairing is effective because it ties feedwater input to both the immediate load change (steam flow) and the resulting level in the drum (level signal). Other signals, like boiler pressure or feedwater temperature, don’t directly represent how much water is needed to satisfy steam demand or to maintain safe drum level, so they’re not used as the two signals in this regulator.