Reciprocating compressors have which components?

• A. A rotor and a stator
• B. A turbine and a shaft
• C. A valve and a receiver
• D. A piston and a cylinder

Answer: (D)

Reciprocating compressors rely on a piston moving inside a cylinder to trap and compress gas. The piston’s back-and-forth motion—driven by a crankshaft—creates alternating low and high pressure inside the cylinder, drawing gas in on the suction stroke and pushing it out on the discharge stroke. The essential mechanical parts that define this type of compressor are the piston and the cylinder, which together provide the positive displacement that accomplishes compression. Other options point to components found in different machines or systems—electric machines use a rotor and stator, a turbine employs a turbine and shaft, and valves or receivers are ancillary parts rather than the defining moving-mechanism pair.