Question 46General Subjects - Assistant Engineer

The correct answer is A) Insufficiently tensioned drive belts. When a belt-driven reciprocating air compressor is operating at a lower than design displacement capacity, one of the common causes is insufficient tension in the drive belts. If the belts are not tensioned properly, they can slip on the pulleys, reducing the effective power transmission from the driver to the compressor. This results in the compressor operating at a lower capacity than its designed specifications. The other options are not the primary causes for lower than design displacement capacity. Misalignment (B) and improper lubrication (C) can contribute to other issues, but do not directly affect the compressor's displacement. Excessive belt tension (D) would actually increase the power transmission and potentially increase the displacement capacity.