CAGI Compressed Air Specialist Practice Exam

A single-acting reciprocating compressor is designed such that the compression of the air only occurs on one side of the piston during its stroke. This means that as the piston moves in one direction, it compresses the air in the cylinder, while the return stroke does not contribute to compression. The single-acting design results in a simpler mechanism and fewer moving parts, making it easier to maintain and operate. In contrast, a double-acting reciprocating compressor compresses air on both sides of the piston, utilizing both the forward and backward strokes to increase efficiency. Rotary screw compressors rely on two rotors to create a continuous flow of compressed air rather than a reciprocating motion. Centrifugal compressors use high-speed rotating impellers to impart velocity to the air, converting that velocity into pressure, which differs fundamentally from the reciprocating design. Thus, the unique operation of the single-acting design specifically focuses on compression in one direction, making it the correct answer.