🔍 Key Concepts

• How a multi-electrode water level control on a fire-tube boiler uses different electrodes for pump on/off, low-water alarm, and low-low-water burner trip • Which electrode in the illustration (B, C, D, E) would most logically be the reference for the normal operating water level (NOWL) versus just safety cutouts • The shaded boiler shell and the relative height of the electrodes compared to what must always stay covered to protect the boiler tubes and furnace crown

💭 Think About

• Look at the vertical positions of electrodes B, C, D, and E. Which one sits roughly at the "mid‑range" where you would want the water level to cycle during normal steaming, rather than way high or way low? • Which electrodes are likely intended only as protection (alarm or burner/pump trip) rather than as the day‑to‑day control band? How does that help you narrow the band that would represent NOWL? • If the water level dropped to just above the lowest electrode, would that really be considered normal operation, or would you already be in a warning or shutdown condition?

✅ Before You Answer

• Identify which electrode is most likely the pump start and which is the pump stop; the NOWL will be between those two points. • Confirm that your chosen range would keep enough water above the area where heat is applied, not allowing the furnace or tubes to be exposed at any point in the cycle (safety margin). • Make sure the option you select describes a band, not a single point, that matches a realistic operating swing of boiler water level.