How Do Different Flow Adjustment Methods Affect Metering Pump Accuracy?

 How Do Different Flow Adjustment Methods Affect Metering Pump Accuracy?

In dosing and chemical injection systems, the key value of a metering pump is accuracy, not simply capacity or speed.

In practice, many dosing deviations are not caused by the pump itself, but by how the flow rate is adjusted.

Different adjustment methods can lead to very different long-term accuracy results.

1. What Determines Metering Pump Accuracy?

In principle, the output flow of a metering pump depends on two factors:

Displacement per stroke

Number of strokes per unit time

Flow adjustment methods work by controlling one or both of these variables. The way this control is applied has a direct impact on dosing stability and repeatability.

2. Stroke Length Adjustment: More Stable at Low Flow

Stroke length adjustment changes the effective displacement of each stroke.

Main characteristics:

Predictable volume per stroke

Good repeatability

Better performance at low dosing rates

For applications with long-term, steady dosing requirements, stroke adjustment often provides better accuracy consistency.

3. Stroke Frequency Adjustment: Flexible but Sensitive at Low Speed

Adjusting the stroke frequency (via electronic control or variable speed) changes how often dosing occurs.

Advantages:

Wide adjustment range

Easy integration with automated control systems

Limitations:

At very low frequencies, fewer dosing events occur per minute

Short-term fluctuations can have a larger impact on total volume

As a result, accuracy may become less stable in low-flow operation.

4. Combined Stroke and Frequency Adjustment: Powerful but Operator-Dependent

Using both stroke length and frequency allows a wide flow range, but it also increases complexity.

If not properly managed, this can lead to:

Excessively short strokes

Frequent parameter changes without recalibration

Gradual deviation between set and actual dosing volumes

This method requires clearer adjustment logic and periodic verification.

5. Other Factors That Influence Accuracy

Beyond adjustment methods, accuracy is also affected by:

Fluid viscosity and temperature changes

Suction conditions and air entrainment

Wear of check valves and internal components

Improper flow adjustment tends to amplify these effects over time.

Conclusion

Metering pump accuracy is not defined by specifications alone.

Choosing the right flow adjustment method — and using it correctly — is essential for maintaining reliable dosing performance over time.

Treating the metering pump as part of the overall system, rather than an isolated device, is the most effective way to ensure long-term accuracy.