How Severe Is Cavitation Damage to Corrosion-Resistant Centrifugal Pumps?

I. Basic Definition of Cavitation

When a corrosion-resistant centrifugal pump conveys acid and alkaline media, if the liquid suction pressure is lower than the saturated vapor pressure of the medium, the liquid vaporizes to form bubbles. These bubbles collapse instantly when flowing into high-pressure zones, and this whole process is defined as cavitation. Though it appears to be a microscopic phenomenon, it causes comprehensive and persistent severe damage to pump equipment.

II. Six Core Hazards

1. Mechanical Damage to Flow-Passing Components

The collapse of bubbles generates microjet impact force equivalent to hundreds to thousands of atmospheric pressures, which repeatedly strikes the impeller and pump casing inner walls:

• Metal materials: Pitting spots first appear on the surface, which gradually develop into honeycomb cavities. In severe cases, blade penetration or impeller cracking occurs.
• Fluoroplastic / engineering plastic anti-corrosion pumps: No rust will form, yet surface roughening and material spalling will take place, directly leading to scrapping of flow-passing components.

2. Sharp Deterioration of Pump Hydraulic Performance

Massive bubbles occupy the flow passages and disrupt normal liquid delivery:

• The flow rate, head and operating efficiency drop drastically simultaneously, and the pump characteristic curve collapses discontinuously.
• Visible symptoms: Violent oscillation of the outlet pressure gauge, drastic fluctuation or even complete loss of flow rate, failing to meet production process conveying requirements.
• Extra energy consumption: Even mild cavitation will shift the pump away from its high-efficiency operating range, raising long-term electricity costs.

3. Severe Vibration and Noise Amplification

High-frequency shocks generated by bubble collapse trigger two major issues:

• Noise: Continuous sharp cracking sounds inside the pump, similar to the friction and impact of gravel, worsening the on-site operating environment.
• Vibration: Shock transfers to the entire pipeline system, loosening pipe joints and disabling field measuring instruments. Long-term alternating loads accelerate fatigue failure of bearings and mechanical seals.

4. Destruction of Precision Sealing and Bearing Components

• Mechanical seals: Vibration causes frequent separation of seal faces, breaking the liquid film and resulting in dry friction, which triggers medium leakage.
• Bearing assemblies: Vibration aggravates wear on raceways and rolling elements, enlarging bearing clearance and causing excessive temperature rise. In extreme cases, cage fracture or bearing seizure may happen.
• Exclusive risk for magnetic pumps: Vibration disrupts the alignment between magnetic steel and the isolation sleeve, causing magnetic steel to collide with and crack the sleeve, resulting in magnetic transmission failure.

5. Vicious Cycle of Equipment Failures

Cavitation and equipment wear aggravate each other:

When conveying high-temperature or easily vaporized media, cavitation can instantly empty the pump chamber, inflicting instantaneous heavy damage to seals and bearings.

6. Concealed Cumulative Wear & Surging Maintenance Costs

Cavitation is highly concealed: Mild cavitation will not cause immediate shutdown, yet it continuously wears down the impeller and pump casing over time. By the time obvious faults emerge, flow-passing components have sustained severe damage, leading to sharply higher costs for pump repair or replacement, as well as a dramatic reduction in overall service life of the equipment.

III. Key Operation Prevention & Control Guidelines

A core principle must be followed during design and daily operation: Required Net Positive Suction Head (NPSHr) of the pump < Available Net Positive Suction Head (NPSHa) of the system.

Four high-risk operating conditions shall be avoided:

• Partially closed inlet valve
• Air leakage in the suction pipeline
• Excessively low liquid level of the storage tank
• Excessively high conveying temperature of the medium