The reciprocating compressor may be damaged if energized when which valve is closed?

• A. Discharge service valve
• B. Suction service valve
• C. Isolation valve in the discharge line
• D. Pressure relief valve

Answer: (A)

If the discharge path is blocked, energizing a reciprocating compressor traps the compressed gas in the cylinder and discharge line. Each compression stroke tries to push gas out, but with nowhere to go the pressure in the cylinder rises rapidly, loading the discharge valves and piping and causing excessive motor torque and heat. This overpressure can damage valves, seals, and components or lead to a mechanical failure. The other valve closures don’t create the same immediate overpressure scenario: closing the suction valve prevents any gas from entering, so the unit would run under no-load conditions; isolating the discharge line still leaves some path for pressure relief, and closing a relief valve would remove safety relief, which is dangerous but doesn’t reproduce the same direct risk as a completely blocked discharge path. Therefore, closing the discharge service valve is the scenario that can most readily cause damage.