Question 55 QMED04 - Boiler Technician-Watertender

The Correct Answer is B **Explanation for Option B (priming and carryover) being correct:** When a boiler is brought onto the main steam header (brought on the line) with its steam pressure significantly higher than the pressure of the boiler(s) already connected, a sudden and rapid equalization of pressure occurs. As the main stop valve is opened, the higher pressure steam rushes violently toward the lower pressure area (the header and the other boiler). This rapid flow and pressure drop within the higher-pressure boiler causes severe turbulence inside its steam drum. This turbulence violently lifts water droplets, foam, or impurities into the steam outlet, a phenomenon known as **priming** or **carryover**. This sends wet steam and potentially damaging chemicals downstream into the turbines, superheaters, or engine systems. **Explanation of why other options are incorrect:** * **A) an overloaded superheater:** While the steam flowing through the superheater will be very rapid initially, the primary danger of unequally pressuring boilers during paralleling is related to water movement in the drum (priming) and the shock to the system, not specifically overloading the heat absorption capacity of the superheater in a damaging way. The superheater damage is usually a secondary risk caused by carryover/priming, not the initial danger itself. * **C) thermal shock:** Thermal shock refers to rapid temperature changes, often seen when cold feedwater is introduced too quickly or during rapid cooling/heating of metal components. While there is a pressure shock, the rapid introduction of steam at a *higher* pressure (but usually similar saturation temperature) than the header does not typically cause the type of rapid metal contraction/expansion defined as thermal shock. The immediate danger is mechanical turbulence and resulting carryover. * **D) low water:** Low water is a critical condition caused by inadequate feeding or excessive blowdown, leading to the overheating of boiler tubes. Bringing a boiler onto the line, even incorrectly, does not directly or immediately cause a depletion of the water level that would lead to a low water condition.