Question 432Steam Plants - Assistant Engineer

The correct answer is D) A malfunctioning auxiliary exhaust make-up steam regulating valve. The lifting of the DC heater relief valve indicates that there is excessive pressure buildup in the DC heater, which is typically caused by a malfunctioning auxiliary exhaust make-up steam regulating valve. This valve is responsible for controlling the flow of steam into the DC heater, and if it is not functioning properly, it can lead to an excessive buildup of pressure, causing the relief valve to lift. The other answer choices are incorrect because they do not directly relate to the lifting of the DC heater relief valve. Excessive deaeration of the feed water (A) or low back pressure in the auxiliary exhaust line (B) would not cause the relief valve to lift. A low water level continually maintained in the DC heater (C) would not lead to the relief valve lifting either, as the relief valve is designed to prevent excessive pressure buildup, not to address water level issues.