Exam Question
(a) What causes cavitation in a Centrifugal pump operation? (6)
(b) If the Engine room Bilge pump not taking suction, explore the probable reasons? (6)
(c) Why is a centrifugal pump started with its discharge valve shut? (4)
Class 4 (4th Engineer)
MEP
📅 Apr 2025
Reference Answer
### (a) What causes cavitation in a Centrifugal pump operation?
Cavitation in a centrifugal pump is a phenomenon characterized by the formation of vapor bubbles (cavities) in the liquid being pumped, followed by their rapid collapse, typically within the high-pressure regions of the pump. This process is highly detrimental to pump performance and longevity. The fundamental cause of cavitation is the local static pressure of the liquid falling below its vapor pressure at the prevailing temperature.
Key factors contributing to cavitation include:
* **Insufficient Net Positive Suction Head Available (NPSHa):** This is the most common cause. NPSHa is the absolute pressure at the suction side of the pump, expressed in meters of liquid head, less the vapor pressure of the liquid. If the NPSHa is less than the Net Positive Suction Head Required (NPSHr) by the pump, cavitation will occur.
Cavitation in a centrifugal pump is a phenomenon characterized by the formation of vapor bubbles (cavities) in the liquid being pumped, followed by their rapid collapse, typically within the high-pressure regions of the pump. This process is highly detrimental to pump performance and longevity. The fundamental cause of cavitation is the local static pressure of the liquid falling below its vapor pressure at the prevailing temperature.
Key factors contributing to cavitation include:
* **Insufficient Net Positive Suction Head Available (NPSHa):** This is the most common cause. NPSHa is the absolute pressure at the suction side of the pump, expressed in meters of liquid head, less the vapor pressure of the liquid. If the NPSHa is less than the Net Positive Suction Head Required (NPSHr) by the pump, cavitation will occur.
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