Full definition
Undesired fluid escape past a seal. Primary causes: worn sealing lip, shaft damage or corrosion (Ra >0.8 μm), incorrect installation (inverted or damaged seal), operating beyond pressure or temperature rating, vibration or shaft misalignment. All leakage requires corrective action. Acceptable leakage for mechanical seals: <1 drop per 5 min per ISO 21049 / API 682.