Which tank is responsible for lowering the temperature and pressure of incoming boiler water?

The correct choice is the blowoff tank, which is designed to handle the discharge of water and sediment from the boiler during blowdown operations. When boiler water is blown off, it often contains both heat and pressure, and this tank allows for the safe release and cooling of this water before it is discharged into the environment or further processed.

While other tanks serve important functions in a boiler system, they do not specifically focus on lowering the temperature and pressure of incoming boiler water. The expansion tank is used to accommodate the expansion of water as it heats and to maintain pressure in the system, rather than directly lowering temperatures or pressures. The feedwater tank stores water to be fed into the boiler and may be heated or treated before use but does not primarily function to reduce temperature or pressure. Similarly, the return tank collects water returning from the heating system but does not serve to cool or depressurize incoming boiler water.

This highlights the specialized role of the blowoff tank in managing the thermal and pressure conditions of water expelled from the boiler, making it the correct answer to the question.