Question 411General Subjects - Assistant Engineer

The correct answer is D) the discharge valve is closed off and there is no change in the discharge pressure. When the discharge valve is slowly closed on a centrifugal fire pump, the discharge pressure should remain unchanged until the valve is nearly closed. This is because the pump is designed to maintain a constant discharge pressure by increasing the pump's rotational speed as the discharge resistance increases. Only when the discharge valve is nearly closed will the relief valve lift to prevent excessive pressure buildup. The other options are incorrect because they do not accurately describe the expected behavior of the system under the given condition of slowly closing the discharge valve.