Flexible Impeller Replacement Troubleshooting Guide

This guide will cover various issues experienced with flexible impellers based on symptoms, what causes the issue, and the remedy for each scenario. 

Troubleshooting 1

Symptoms

• End faces hard and either polished or cracked, like carbon
• Some or all blades completely missing

Cause

• Dry running; lack of water in pump
• Temporary suction blockage
• Leaking suction plumbing

Remedy

• Do not run pump for more than 20 seconds without liquid
• Install a liquid sensor/temperature alarm
• Check suction plumbing, strainers, and through hull fittings for blockages and leakage
• Arrange discharge plumbing to trap liquid in the pump

Troubleshooting 2

Symptoms

• Pieces missing from the middle of blade tips
• Blade edges are hollowed out
• Pitting is evident on cam and the inside of pump ports, and on ends of impeller

Cause

• Cavitation, i.e., too much vacuum on inlet is causing water to boil inside pump

Remedy

• Reduce pump speed
• Increase inlet plumbing diameter
• Reduce inlet plumbing length and remove unnecessary restrictions
• Reduce cam thickness

Troubleshooting 3

Symptoms

• Worn blade tips, cam imprint on edges
• Worn end faces
• Worn impeller drive and shaft wear

Cause

• Abrasive wear from fluid in pump
• Heat exchanger/cooler blockage
• High discharge pressure

Remedy

• Check discharge plumbing for partial blockages
• Increase discharge pipe diameter

Troubleshooting 4

Symptoms

• Impeller appears to have swollen
• Blades appear wider than impeller hub
• Rubber may feel sticky

Cause

• Chemical attack, more common with oily bilge water or diesel transfer

Remedy

• Ensure impeller is rinsed after use
• Remove impeller when not in use
• Remove impeller for long-term storage

Troubleshooting 5

Symptoms

• Blades have some or severe permanent set

Cause

• Normal use of impeller
• Long-term storage in pump
• Normal end of impeller life

Remedy

• Refit impeller to rotate in opposite direction
• Remove impeller for long-term storage
• Replace impeller

Troubleshooting 6

Symptoms

• Blades cracked about halfway up the length
• Some blades missing
• Reduced flow

Cause

• Normal end of impeller life
• High discharge pressure

Remedy

• Replace impeller; check for impeller pieces in discharge plumbing
• Reduce outlet restrictions or increase outlet plumbing diameter