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Biggest 3 Causes of why your impeller can fail

An integral component to a centrifugal pump’s functionality is its impeller. Without an impeller, centrifugal force cannot be generated upon the entering liquid. Thus, without an impeller, a centrifugal pump cannot function at all whatsoever. For this reason, proper care is necessary for a pump’s impeller so as to prevent pump downtimes and ensure maximum length of a pump’s continual operation. Damaged impellers can also lead to low flow in pumps. The top 3 most common causes for impeller failures are due to cavitation, erosion and corrosion.

Cavitation

Cavitation is a great danger for any centrifugal pump is cavitation. “Commonly seen on the pump impeller, cavitation is caused by a pressure difference, either on the pump body or the impeller. A sudden pressure drop in the fluid causes the liquid to flash to vapor when the local pressure falls below the saturation pressure for the fluid being pumped.”1 Cavitation can quickly cause an impeller to practically disintegrate rapidly if not remedied as soon as possible. Similar to disintegration, erosion is also a cause for impellers to fail.

Erosion

Erosion of an impeller is usually due to small, hard particles (such as sand) coming into contact with the impeller, resulting over time in a gradual wearing down of the entire impeller. Erosion of a pump’s parts can be difficult to totally prevent, yet there are two major ways to minimize erosion of an impeller: Firstly, by “Reducing the flow velocities in every part of the pump”1 and secondly by “Design the pump in such a way that the flow velocities through the close-running clearances are low.”1 Besides erosion, which is due to solids, corrosion is just as dangerous, if not more so, for a pump’s impeller.

Corrosion

Corrosion usually occurs due to an excessively low pH, usually around 2.0-3.0, which is very acidic. Over time, corrosion essentially eats away at parts within a pump. This is why appropriate materials of an impeller are crucial: For if a pump’s impeller is made of cast iron and caustic fluids will be pumped through it, then the impeller will quickly deteriorate and will also likely result in other corrosive damages to the pump. Besides frequent monitoring of a pump’s status when pumping caustic fluids, other solutions to preventing pump failures include “adopting suitable design parameters during the design stage and selecting suitable materials for components like impellers, valves and pipefittings. Anti-corrosion coatings reduce corrosion damage and improve pump efficiency and the economic life of the pumping system.”4

Summary

Time after time, the best solutions to critical problems plaguing centrifugal pumps begin in the design and planning stage of a pump. It is crucial to choose the most appropriate parts for a pump in order to prevent catastrophic failures in the long-term: Even if this means spending more on an impeller of a higher-standard material or anti-corrosive coatings. For these measures are surely able to increase the durability and long-term efficiency of a centrifugal pump, reducing downtimes and thereby continually generating the same amount of flow over time.

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1 https://empoweringpumps.com/sulzer-maximizing-pump-efficiency-through-reduced-corrosion-erosion/

2 https://www.corrosionpedia.com/corrosion-prevention-for-water-pumps-valves-impellers-and-fittings/2/6512

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