Question 233Steam Plants - 1st Asst/Chief

The correct answer is B) improper operation of the DC heater. Excess free oxygen in the boiler feed water is typically caused by improper operation of the deaerating feed water heater (DC heater). The DC heater is designed to remove dissolved oxygen from the feed water by heating it, which causes the oxygen to be released. If the DC heater is not functioning properly, it will not effectively remove the dissolved oxygen, leading to excess free oxygen in the boiler feed water. The other options are incorrect because they do not directly contribute to excess free oxygen in the boiler feed water. Improper operation of the gland exhauster, steam leaks through the turbine glands, and vapor lock in the boiler feed pump may have other impacts on the boiler system, but they do not specifically result in excess free oxygen in the feed water.