Question 55 on boiler foundations, October 8: (A certain score will be given to the top 40)
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If the boiler load increases suddenly, the water level drops immediately and rapidly ( ) (Wrong). Thank you for your support; correct answers earn +6 points, while incorrect answers result in a loss of 45 points plus +3 points
××××××Rise! ! ! ! !
The boiler load increases suddenly, and the water level drops rapidly immediately (incorrect)
The boiler load increases suddenly, and the water level drops rapidly immediately (incorrect)
The boiler load increases suddenly, and the water level drops rapidly immediately (X)
The boiler load increases suddenly, and the water level drops rapidly immediately (incorrect)
When the boiler load increases suddenly, the water level drops rapidly immediately (x). At a stable load, the volume of steam inside the water wall tubes remains constant; the water supply volume equals the evaporation volume, and thus the drum water level stays stable. There are two scenarios for a sudden increase in load: in one case, the amount of fuel entering the furnace remains unchanged, while the external load increases suddenly. Under such circumstances, the steam pressure must decrease. Due to the corresponding drop in saturation temperature, the heat stored in the metal and the boiler water is released primarily in the form of vaporization of the boiler water within the water wall. The vaporization of the boiler water increases the volume of steam inside the water wall tubes, while the excess boiler water is discharged into the drum. At this point, the water supply volume has not yet increased; the drop in water level caused by the material imbalance takes some time to become apparent, so macroscopically it appears as an immediate rise in water level. After some time, when the volume of steam inside the water wall tubes stops increasing and reaches equilibrium, and the material imbalance no longer has a significant effect on the water level, the water level gradually returns to normal. If the water supply is not increased in time, a negative water level will occur. Another scenario is an abrupt increase in the boiler’s evaporation rate due to too rapid an increase in the fuel supply to the boiler. In this case, the heat absorption by the water wall increases suddenly. The amount of steam generated inside the water wall tubes increases, and as the volume of steam rises, it rapidly pushes the water in those tubes toward the steam drum, causing the water level to rise instantly. It can be seen from this that, in any case, a sudden increase in load will inevitably cause the water level to rise instantly.
The boiler load increases suddenly, causing the water level to drop rapidly immediately (boiler tube rupture)
The boiler load increases suddenly, and the water level drops rapidly immediately (incorrect)