Size a chemical dosing pump from the active mass required per hour, then verify solution strength, density, backpressure, and turndown. A stroke setting is not proof of delivered dose: measure actual output with a calibration column before commissioning and whenever the process or chemical solution changes.
Chemical dosing pump sizing equation
Start with the required dose, not the pump size on the shelf. For continuous flow:
active mass (g/h) = dose (mg/L) × flow (m³/h)
solution volume (L/h) = active mass (kg/h) ÷ [active fraction × solution density (kg/L)]
Example: 100 m³/h at 2 mg/L needs 200 g/h, or 0.20 kg/h, of active chemical. With a 10% active solution at 1.10 kg/L, the solution demand is 0.20 ÷ (0.10 × 1.10) = 1.82 L/h. Add design allowance only after the process team has agreed peak-flow and water-quality cases; a pump margin is never a substitute for a jar test or residual verification.
Inputs that determine capacity, materials, and pressure
| Vendor input | Why it matters | Risk if omitted |
|---|---|---|
| Minimum, normal, and maximum dose; minimum and peak flow | Establishes the usable pump range | A pump that is stable at only one condition |
| Chemical name, concentration, SDS, and temperature | Selects wetted materials and ventilation needs | Corrosion, seal swelling, or exposure risk |
| Injection pressure, pipe run, elevation, valves, and pulsation dampener | Establishes actual differential pressure | Output falls as backpressure increases |
| Injection point and mixing requirement | Determines injection quill/check valve and contact time | Chemical enters the line but does not disperse |
| Control signal, flow interlock, and duty/standby requirement | Defines operating integration | Chemical feeds while process flow has stopped |
Differential pressure must include process pressure at injection, pipe/valve loss, and static head. A catalogue duty stated at one pressure is not the installed duty without checking the curve. The Betaqua Dosing Pump page, for example, lists model output at different pressures; match that curve to measured site data rather than a nominal flow alone.
Calibration-column procedure
EPA identifies calibration columns as a way to verify chemical feed and recommends routine accuracy checks for chemical-feed systems (EPA, LT1ESWTR Turbidity Provisions Technical Guidance Manual).
- Fill the calibration column and stabilise stroke/speed, backpressure, and suction conditions as they will operate.
- Record the starting volume and run the pump for a measured period, such as 60 or 120 seconds.
- Calculate
L/h = volume used (L) ÷ elapsed time (h). Repeat at least three times and use a consistent result. - Compare actual output with the target, adjust the setting, and repeat the measurement.
- Log the date, chemical, density where available, setting, pressure, operator, and result. Re-test after diaphragm/valve work, a solution change, or a process-pressure change.
Do not calibrate by discharging into an unsafe drain. Follow the chemical SDS, use the required PPE, and return test solution only to a tank permitted by the facility procedure.
Interlocks and pre-injection checks
- Interlock the pump to a flow signal or process permissive so it cannot overdose a stopped stream.
- Confirm the foot valve is submerged, the suction line is air-tight, and the injection check valve opens at the intended pressure.
- Verify flow direction, electrical protection, tank ventilation, secondary containment, and relief routing against the site design.
- For critical chemicals, provide low-level alarming and a tested duty/standby changeover procedure.
- Confirm the process result—such as residual, pH, conductivity, or a jar-test parameter—after changing pump output.
Buyer data sheet for a defensible selection
Send PT Beta Pramesti Asia the chemical and SDS, active dose, concentration/density, minimum-normal-maximum flow, injection pressure, piping sketch, temperature, control requirement, and duty/standby target. This lets us review a chemical metering pump, injection point, and accessories without guessing.
Where a project separately sources water-treatment accessories, Watermart dosing pumps are a useful complementary reference. Final selection must still follow measured process conditions and chemical compatibility.