Question 49 UFIV02 - Assistant Engineer - UFIV

The Correct Answer is D ### Why Option D is Correct Option D states: "The gauge glass should be blown down twice; first with the lower cutout valve open and then with the upper cutout valve open." This procedure is the standard, safest, and most effective method for ensuring the gauge glass accurately reflects the boiler water level. The purpose of blowing down the gauge glass is to clear any potential obstructions (like scale, sediment, or sludge) from the piping connections leading to the water column and the gauge glass itself. 1. **First Blow (Lower Valve Open):** By opening the main blowdown valve and keeping the **lower (water) cut-out valve** open while the upper (steam) cut-out valve is closed, high-pressure steam and water are forced to rush down and out through the water leg connection (the lower piping). This clears any sediment or sludge accumulated in the lower connection piping (the water side) and the lower section of the glass fittings. 2. **Second Blow (Upper Valve Open):** After closing the lower valve, opening the main blowdown valve while the **upper (steam) cut-out valve** is open ensures that the steam connection (the upper piping) is cleared of any condensate, scale, or sludge. This verifies that the full steam pressure is reaching the top connection. 3. **Restoration:** After both sides are blown down and verified, the main blowdown valve is closed, and both the upper and lower cut-out valves are reopened slowly, allowing the water level to stabilize and return to the proper indication. This two-step process individually verifies the clear passage of both the water connection (bottom) and the steam connection (top), which is critical for an accurate level reading. ### Why Other Options Are Incorrect **A) The gauge glass should be blown down once with both the upper cut-out and lower cut-out valves open simultaneously** * **Incorrect:** While this procedure clears the glass itself, it does not guarantee that either the specific lower (water) connection piping or the specific upper (steam) connection piping is clear of obstructions. Debris lodged in the bends of the piping connections can remain, causing a false water level reading. **B) The gauge glass should be blown down twice; first with the upper cutout valve open and then with the lower cutout valve open** * **Incorrect:** This procedure reverses the standard order, though it achieves the goal of clearing both sides. However, the standard and safer procedure is typically to clear the water side (lower) first, followed by the steam side (upper). More importantly, the critical sequence is to ensure both sides are blown down *individually*, which this option does achieve, but D represents the accepted best practice sequence. **C) The gauge glass should be blown down once with the lower cutout valve open** * **Incorrect:** This procedure would only clear the lower water connection and the lower fittings. The upper steam connection piping would not be cleared or verified, potentially leading to a false level reading if the steam connection is partially blocked.