Question 400Steam Plants - Assistant Engineer

70% to pass

Which of the following statements describes the effects that dissolved oxygen has on boiler internal surfaces with changes in temperature and pressure?

AIt increases the corrosive effect with lowered pressure and increases its corrosive effect with increased temperature.
BIt decreases the corrosive effect when both pressure and temperature are increased.
CIt increases the corrosive effect with increased pressure and decreases its corrosive effect with increased temperature.
DTemperature and pressure have no effect on the corrosive effect of dissolved oxygen.
AI Explanation

The correct answer is C: It increases the corrosive effect with increased pressure and decreases its corrosive effect with increased temperature. This is because dissolved oxygen becomes more corrosive at higher pressures, as the increased pressure forces more oxygen to dissolve in the water. However, at higher temperatures, the solubility of oxygen decreases, reducing the corrosive effect. The other options are incorrect because: A) The statement about the effects of pressure and temperature is reversed. B) Increased pressure and temperature both increase the corrosive effect of dissolved oxygen. D) Temperature and pressure do have an effect on the corrosive nature of dissolved oxygen.

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Official Resources
46 CFR Machinery & Electrical 46 CFR Engineering USCG National Maritime Center
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