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Cavitation Damage will manifest itself on the impeller in the form of pitting. There are 5 basic types of Cavitation damage:
- Suction Cavitation: Caused by low NPSH. This type of cavitation usually shows up at the leading edges of the impeller vanes on the trailing edge.
- Air Entrainment: Not classified as cavitation, air bubbles in the pumpage will collapse as they become pressurized when the enter the impeller vanes. The damage done by the collapsing air bubbles looks like cavitation damage and shows up at the leading edges of the impeller vanes. Damage due to air entrainment can easily be mistaken for Suction Cavitation.
- Suction Recirculation: Caused by operating the pump at too low of a flow rate. Damage from this type of cavitation usually shows up in the form of pitting on the low pressure side of the impeller vane (trailing edge), about 1/2 of the distance along the vane.
- Discharge Recirculation: Caused by operating the pump at low flow rates. Usually shows up at the impeller discharge vane tips in the form of pitting or errosion.
- Discharge Cavitation: Caused by operating a pump at too high of flow rate. This type of cavitation can be severe and will exhibit itself at the OD of the impeller at both the impeller vane tips and on the shrouds of the impeller. Discharge cavitation may even tend to bow out the shrouds of the impeller between the impeller vanes.
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