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Best practices for reliable canned motor pump operation
In chemical, petrochemical and refrigeration applications, pumps rarely fail without warning, but the early signals are often overlooked. Unplanned downtime is frequently caused not by a single defect, but by a combination of design decisions, operating conditions and process changes over time.
Industry experience shows many pump issues can be traced back to operating deviations rather than design flaws. This is especially true for sealless canned motor pumps, where reliability depends on consistent process conditions and a clear understanding of how the pump interacts with the system.
Reliability starts before commissioning
From the very beginning, reliable pump operation depends on accurate process data. Medium properties such as temperature, density, vapor pressure and viscosity determine not only material selection, but also bearing design, cooling concepts and hydraulic sizing.
Even small deviations, for example a change in density caused by temperature fluctuations, can significantly affect bearing loads or motor cooling. Over time, these deviations may lead to wear patterns that remain unnoticed until pump performance declines.
Best practice: Define operating parameters as precisely as possible and reassess them whenever process conditions change.
Avoiding the most common operational risks
Field data shows the majority of pump-related failures are linked to changing operating conditions. Typical risk factors include:
- Foreign particles introduced during maintenance or commissioning
- Pressure losses in the suction line caused by filters or pipe routing
- Insufficient consideration of NPSH margins
- Operation below minimum flow rates
- Temperature increases that affect motor cooling and bearing lubrication
These issues often develop gradually, making early detection difficult. Monitoring critical indicators such as temperature, fill level and pressure differentials can help identify unfavorable conditions before damage occurs.
Cavitation and dry running: Small causes, big impact
Cavitation remains one of the most frequent causes of damage in centrifugal pumps. It is often triggered by pressure drops on the suction side, insufficient NPSHa or unexpected changes in flow rate.
Dry running presents an even greater risk. In sealless pumps, the pumped liquid serves as both a lubricant and coolant. If that liquid is absent, even briefly, bearing damage and rotor contact can occur within seconds.
Best practice: Maintain adequate safety margins and ensure monitoring and protective systems are properly applied for the specific application.
Learning from proven application experience
Long-term studies and operating experience across multiple industries show stable pump operation is rarely the result of a single measure. Instead, reliability comes from understanding how design, operating parameters and monitoring systems work together.
Many of the most effective preventative measures are simple, but only when the underlying relationships are fully understood.
Want the full picture?
To support system planners and operators, HERMETIC has compiled proven application knowledge into a practical guide:
“10 Tips for Smooth Canned Motor Pump Operation”
The booklet explains the most common causes of pump faults, their technical background and proven methods to prevent them, from material selection and suction conditions to cavitation prevention and dry-running protection.
