Twin-Rotary Phase Synchronization Failure → Abnormal Vibration Increase

Question

Accepted Answer

Wear or loss of dowel pin maintaining 180° phase angle between upper and lower cylinders. Check: Measure compressor housing vibration with vibration meter — normal < 2.8 mm/s (RMS); stop immediately if > 4.5 mm/s. Disassemble and inspect dowel pin: verify diameter tolerance within ±0.01 mm What to do: Replace worn dowel pins with new → reassemble upper/lower cylinders with uniform torque 15–20 N·m using torque wrench → replace oil with specified grade (VG32–46) → re-measure vibration after repair (target ≤ 2.0 mm/s) Crankshaft eccentric journal wear → unequal stroke between upper and lower rotors. Check: Measure crankshaft eccentric journal roundness with micrometer — replace if deviation > 0.02 mm. In vibration frequency analysis, strong 2× rotational frequency component indicates stroke imbalance What to do: Replace crankshaft → verify new part eccentric journal roundness before assembly → measure vibration after reassembly: confirm ≤ 2.0 mm/s. If still elevated, inspect and adjust balance weights High-viscosity oil (VG68+) or assembly defect (uneven bolt torque). Check: Check oil viscosity: verify VG grade from label or viscometer — replace immediately if VG68 or higher. Review recent maintenance history: look up cylinder bolt torque records What to do: Replace all oil with specified viscosity (VG32–46) → verify cylinder bolt seating and re-torque to 15–20 N·m with torque wrench → re-measure vibration: target ≤ 2.8 mm/s

Twin-Rotary Phase Synchronization Failure → Abnormal Vibration Increase

Likely causes

Wear or loss of dowel pin maintaining 180° phase angle between upper and lower cylinders

Crankshaft eccentric journal wear → unequal stroke between upper and lower rotors

High-viscosity oil (VG68+) or assembly defect (uneven bolt torque)

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