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Plant Engineering Calculator

Updated Sep 18, 2026

Pump Minimum Flow Recirculation Calculator — Bypass Flow, kW & Heat

Calculate required bypass flow when process demand falls below a pump minimum-flow limit and estimate recirculation hydraulic power.

Live calculationWorking shownPrivate in browser

Inputs

Results

Required bypass 15.00 L/s
Hydraulic recirculation 7.35 kW
Input equivalent 9.81 kW
Process share 62.5 % of minimum
More actions

Shared links reopen these inputs. Recent and saved calculations stay in this browser unless you clear site data.

Formula

Qbypass=max(0,Qmin−Qprocess); Phyd=ρgQbypassH.

Your calculation, step by step

These steps use the values currently entered above so the result can be checked independently.

  1. 1.Bypass = max(0, 40.000 − 25.000) = 15.000 L/s.
  2. 2.Convert bypass = 15.000 ÷ 1000 = 0.015000 m³/s.
  3. 3.Hydraulic recirculation power = 1000.00 × 9.80665 × 0.015000 × 50.00 ÷ 1000 = 7.3550 kW.
  4. 4.Input-equivalent screen = 7.3550 ÷ (75.00% ÷ 100) = 9.8066 kW.
  5. 5.Process flow ÷ OEM minimum = 25.000 ÷ 40.000 × 100 = 62.50%.

How to use this calculator

  1. Enter measured or design values using the units shown beside each field.
  2. Review the live results and the substituted calculation steps before using the estimate.
  3. Check the assumptions below, then continue to a related calculator when the next engineering decision needs another model.

Worked example

A pump requiring 40 L/s minimum with 25 L/s process demand needs 15 L/s recirculation.

Assumptions and limits

  • Minimum stable/thermal flow must come from the pump OEM or validated engineering basis.
  • A bypass protects the pump but can waste energy and heat the fluid.
  • The input-equivalent kW is a screening conversion using the entered efficiency, not a full pump/system-curve model.

How to interpret the result

Treat the primary result as an engineering screening value, then use the secondary outputs to understand scale, energy or operating impact. Confirm site measurements, equipment limits and applicable standards before making a design or control change.

Questions engineers ask

Where should minimum continuous pump flow come from?

Use the pump OEM or a validated engineering basis such as minimum continuous stable or thermal flow. It is not safely inferred from rated flow by one universal percentage.

What happens when process flow already exceeds the minimum?

Required recirculation is zero because Qbypass = max(0, Qmin − Qprocess). The owner still shows the process share of minimum flow so the operating margin is visible.

Is all bypass hydraulic power necessarily wasted as heat?

A recirculation loop does not deliver useful process flow and its hydraulic energy ultimately appears as pressure/thermal loss somewhere in the loop, but actual fluid heating and motor input depend on pump efficiency, valve/orifice behavior and where the bypass returns.

Continue the calculation

Use the next calculator in the same engineering workflow instead of restarting from search.

pump bypass recirculation losspump powerpump system curve
Methodology. MAXScanner shows the governing formula, entered values and calculation outputs so the estimate is auditable. The calculator is a screening aid; assumptions and equipment-specific limits remain part of the engineering review.