Question 58 OSE01 - Chief Engineer - OSV

The Correct Answer is D **Explanation of why option D is correct:** A boiler water column is designed to display the water level within the boiler drum. The water column typically includes three tricocks (test cocks) used to verify the operational state of the level gauge glass and confirm the actual water level independently. 1. **Uppermost Tricock (Steam Space):** The uppermost tricock is mounted above the Normal Operating Water Level (NOWL) connection point. Since the water level is at the NOWL, this tricock is located in the steam space of the boiler drum. When opened, high-pressure steam will issue from it. 2. **Lowermost Tricock (Water Space):** The lowermost tricock is mounted below the Lowest Permissible Water Level (LPWL) connection point (and well below the NOWL). This tricock is always submerged in the boiler water/liquid space during normal operation. When opened, water (and sometimes a mixture of water and flash steam) will issue from it. 3. **Middle Tricock (NOWL Reference):** The middle tricock is typically positioned close to, or exactly at, the Normal Operating Water Level (NOWL). Since the actual water level is precisely at the NOWL, the interface between the steam and water phases is occurring at or very near this point. Due to normal boiler turbulence, drum motion (on a vessel), and slight fluctuations inherent in operation, the middle tricock could be momentarily in the steam space or momentarily in the water space. Therefore, when opened, **either** steam **or** water could issue from the middle tricock. Therefore, option D correctly identifies the outcome for each tricock position based on the water level being at the NOWL. **Explanation of why the other options are incorrect:** * **A) Steam should issue from the uppermost tricock, and water should issue from both the middle and lowermost tricocks.** * This is incorrect because if water were issuing consistently from the middle tricock, the water level would be definitively above the NOWL. When the level is precisely at the NOWL, the middle tricock's output is ambiguous (steam or water). * **B) Water should issue from each of the uppermost, middle, and lowermost tricocks.** * This is definitively incorrect. If water issued from the uppermost tricock, the boiler would be grossly overfilled (priming risk), meaning the level is far above the NOWL and likely entering the steam outlet pipes. The uppermost tricock must issue steam at the NOWL. * **C) Steam should issue from both the uppermost and middle tricocks, and water should issue from the lowermost tricock.** * This is incorrect because if steam were issuing consistently from the middle tricock, the water level would be definitively below the NOWL (low water condition). At the NOWL, the middle tricock's output is uncertain/variable.