Question 138Steam Plants - Assistant Engineer

The correct answer is C) Taking on makeup feed. When the vessel takes on makeup feed, it introduces additional dissolved oxygen into the boiler feedwater system. This dissolved oxygen is then carried over to the main condenser, where it can contribute to corrosion and scale formation in the condenser tubes. The other options are not directly related to the introduction of dissolved oxygen into the condenser. Priming in the boiler, dumping auxiliary exhaust steam, and excessive DC heater temperature do not necessarily result in dissolved oxygen being carried over to the main condenser.