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Pump slip is the internal leakage that makes a pump deliver less fluid than its theoretical output. This short guide explains the causes, the effect on performance, a simple worked example, and practical steps you can take to reduce slip and keep systems efficient.
Pump slip is the difference between the theoretical flow a pump should produce and the actual flow it delivers in service. In simple terms, some fluid leaks internally from the discharge back to the suction side, so the pump does not achieve its nominal output.
All pumps can experience slip in one form or another, but it is most obvious in positive displacement pumps such as gear pumps, lobe pumps and progressive cavity pumps. Centrifugal pumps also suffer efficiency losses that are often described as slip in design texts, but the mechanisms differ from those in displacement pumps.
Excessive slip reduces delivered flow, wastes energy and generates heat. For abrasive fluids, leakage through clearances accelerates wear and can cause rapid performance decline. In metering and dosing applications even small amounts of slip will reduce accuracy.
Two practical approaches are common:
If slip increases suddenly or exceeds the acceptable tolerance for your application, inspect for wear, damage or contamination. For metering duties, replace or rebuild pumps when slip pushes accuracy out of specification. For general duties, plan rebuilds when measured slip reaches a threshold you set during commissioning, commonly 10 to 15 percent for many positive displacement applications.
Pump slip is normal to a degree but should be managed. Track actual flow against expected flow, control system pressure and viscosity where possible, and keep a planned maintenance regime to prevent clearances growing. If you would like a recommendation for replacement parts, get in touch.
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