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Reciprocating Piston Ring Wear — Increased Blow-By and Oil Dilution

Likely causes

Piston ring wear — operation exceeds 40,000 hours, cylinder clearance exceeds 0.15 mm

Check: Hold hand near crankcase breather — stop immediately if hot air or oil mist detected. Measure oil viscosity (take sample) — if more than 20% below normal, refrigerant dilution confirmed. Check crankcase oil for foaming

What to do: Measure cylinder bore top/middle/bottom with bore gauge → rebore if taper exceeds 0.05 mm → replace piston ring set (ring end gap = bore diameter × 0.003~0.004) → full oil change + clean oil strainer → re-sample oil after 48 hours operation

Oil contamination or incompatible viscosity — oil film collapse

Check: Verify refrigerant-oil compatibility (R22 = MO 150SUS, R404A = POE 68, R410A = POE 32). Replace if ISO cleanliness class exceeds 16/14/11

What to do: Replace with manufacturer-specified oil → clean oil strainer → install suction line oil trap (separates refrigerant and oil, prevents crankcase dilution)

Field tip

Field check for blow-by: hand near crankcase breather → hot air + oil mist = stop immediately. Plan preventive replacement at 40,000 hours.

All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.

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