Question 178General Subjects - 1st Asst/Chief
70% to passAfter a disassembly of a single stage centrifugal pump, one finds the outer circumference of the impeller badly pitted and worn. Not having a spare impeller on board, it is decided to turn down the impeller to eliminate the wear/pitting. What will be the pump capacity, in GPM, after the reduction of impeller diameter by 0.5 inches? GIVEN: Original pump capacity = 30 GPM Original impeller diameter = 8 in.
A24.78 GPM
B26.37 GPM
C28.12 GPM
DCapacity would not change.
AI Explanation
The correct answer is C) 28.12 GPM. The reasoning is as follows: The capacity of a centrifugal pump is directly proportional to the square of the impeller diameter. When the impeller diameter is reduced by 0.5 inches, from 8 inches to 7.5 inches, the new capacity can be calculated as: (7.5/8)^2 * 30 GPM = 28.12 GPM. This is because the pump capacity is reduced in proportion to the square of the impeller diameter reduction. The other options are incorrect because they do not accurately reflect the impact of the 0.5-inch impeller diameter reduction on the pump capacity.
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