The number of eductors a tank needs is the larger of two results: the quantity required for circulation and the quantity required to cover the tank geometry. A turnover calculation may say four units are enough, while the layout needs six to sweep around coils, baffles or a long rectangular footprint. Final quantity must therefore combine hydraulic performance with a plan-view and elevation layout.
Calculate quantity from circulation first
Start with the working volume and a preliminary circulation target. The tank mixing eductor sizing calculator uses Qrequired = V/T as a screening method. Then obtain total circulation per eductor from model-specific performance data at the pressure available at the inlet.
Nhydraulic = ceiling(Qrequired ÷ Qc)
Qc must be the verified total circulation for the selected configuration and operating pressure. Do not multiply pump flow by a universal induced-flow ratio. Manufacturer data shows that circulation and effective flow field change with model, size and pressure.
Check the motive-flow requirement
The pump must deliver approximately N × Qm at the required inlet pressure after header losses. If adding another eductor moves the pump to a lower-flow or lower-pressure operating point, recalculate every branch instead of assuming each unit keeps its original performance.
Calculate quantity from coverage and tank geometry
Draw the tank in plan and elevation. Add coils, columns, baffles, suction lines, level instruments and other internals that can interrupt the jet. Place preliminary eductors so their effective flow fields sweep the bulk liquid rather than collide immediately with a wall or another jet.
| Tank condition | Quantity implication |
|---|---|
| Tall, narrow vessel | May need units at more than one elevation or an upward component to prevent vertical stratification. |
| Wide or rectangular tank | Often needs multiple flow paths even when total circulation is modest. |
| Coils or dense internals | Can divide the tank into zones that require separate sweeping directions. |
| Minimum and maximum level vary widely | Placement must retain submergence and useful coverage through the operating range. |
| Fast-settling solids | May require more local bottom velocity and a solids-specific test rather than a turnover-only design. |
The coverage result is Ncoverage. Use Npreliminary = max(Nhydraulic, Ncoverage), then verify the pump and header again.
Check minimum, normal and maximum liquid levels
A layout that works at maximum volume can expose an eductor or create a short surface loop at minimum level. Conversely, a unit placed low enough for minimum level may not generate adequate upper-tank movement when the tank is full. Review all three levels and the transition between them.
Avoid short-circuiting
Do not aim discharge directly into the recirculation suction or allow every jet to circulate only around the tank perimeter. The objective is a useful bulk-flow path through the process volume. Separation between suction and return, jet direction and tank internals should be reviewed together.
Balance the header
Long or asymmetric headers may deliver different pressure to different eductors. Use branch loss calculations, suitable header sizing and pressure measurements during commissioning. Equal connection sizes do not prove equal flow.
Hypothetical quantity example
This example demonstrates the decision sequence; the values are not product performance claims.
- Hydraulic calculation: 96 m³/h required circulation
- Verified circulation for the candidate at design pressure: 24 m³/h per unit
- Nhydraulic = ceiling(96 ÷ 24) = 4
- Layout review: a long tank with a central coil requires three sweeping zones on each side
- Ncoverage = 6
- Preliminary selection = 6 units
The engineer must now confirm that the pump supplies the combined motive flow for six units at the required pressure. If it cannot, options include changing model size, revising the header, using another pump operating point or changing the mixing concept.
Quantity review checklist
- Working volume at each operating level is documented.
- The process acceptance condition is measurable.
- Total circulation per unit comes from verified model data.
- Plan and elevation drawings show every effective flow field.
- Tank internals and dead zones are included.
- The pump curve and system losses support all branches.
- Material, solids passage and maintenance access are acceptable.
- Commissioning measurements and observations are defined.
Next, review eductor placement and orientation and pump sizing for the complete header.
Review Mixing Eductor options or send a tank drawing and pump curve to Jeltecn.
Technical reference
For examples of model-specific circulation and effective flow-field data, see the Spraying Systems Co. 46550 product data. Use the selected supplier’s current performance documentation for the final calculation.