🔍 Key Concepts

• Water column on a boiler shows the same water level as in the drum when the upper and lower connections are clear. • Each tri-cock is at a fixed height; what comes out (steam vs water) tells you whether that point is above or below the actual water level. • At normal operating water level (NOWL), the gauge glass shows where the steam-water interface is relative to the three tri-cocks.

💭 Think About

• Look carefully at the illustration: is the NOWL shown above, below, or between any of the three tri-cocks on the water column? • For each tri-cock, ask: is its port located above the water line (so it would open to steam space) or below the water line (so it would open to water)? • Which answer choice best matches the pattern of steam vs water you would expect at those three vertical positions when the boiler is at NOWL?

✅ Before You Answer

• Be sure which tri-cock is uppermost, middle, and lowermost in the illustration before matching to the choices. • Confirm in your mind that steam will issue from any tri-cock that opens into the steam space and water from any tri-cock that opens into the water space at NOWL. • Verify that your chosen option is consistent for all three tri-cocks at the same, single water level—no contradictions.