How to Read a Metering Pump Selection Table and Lock the Right Model Fast

A metering pump selection table looks simple until someone circles the first row whose flow is close enough. The pump arrives and the pressure is short, the head material is wrong, or the motor voltage does not match the site. The chart was fine. The reading method was not. Here is how we walk customers through a metering pump selection table in practice.

What Columns Sit in a Metering Pump Selection Table

Open a NEWDOSE-style mechanical diaphragm chart and you usually see series, model, capacity (L/h), pressure (bar), stroke length (mm), diaphragm diameter (mm), speed (SPM), volume per stroke (ml/stroke) and motor power (W). Solenoid charts add control type, suction lift and power supply.

Those columns are not decoration. Capacity and pressure decide whether chemical reaches the injection point. Materials decide whether the head survives the chemical. Motor and power decide whether you can even wire it. Scan in that order and the page shrinks fast.

Write the Duty Down Before You Open the Chart

A metering pump selection table is a filter, not a guessing game. Before you touch a row, write four things: maximum flow in L/h, actual pressure at the injection point, chemical name with concentration and temperature, plus power and control. Miss any of them and the model you circle is guesswork.

Size flow on the peak dose with about 20% to 30% margin, and keep normal running between roughly 30% and 90% of rated capacity. Pressure is the pressure in the pipe or vessel you are injecting into, not a marketing “max” figure. Open basins look like low-pressure jobs on the chart, but they often still need a back pressure valve on the discharge.

Match Flow and Pressure Columns Together

Take the NDWS series as a concrete read: NDWS-18/1.6 is 18 L/h at 16 bar; NDWS-68/1.0 is 68 L/h at 10 bar; NDWS-213/0.5 is 213 L/h at 5 bar. Inside one series, higher flow often means lower pressure. That trade-off is normal for diaphragm designs, not a printing error.

When you use a metering pump selection table, strike out every row whose pressure is below the injection point first, then pick a flow that fits among what remains. Doing flow first and pressure second is how people end up with “enough liters, not enough bar.” Solenoid charts work the same way: DFD-02-07 is 2 L/h at 7 bar, DFD-12-07 is 12 L/h at 7 bar. Same pressure screen, different flow bins.

Unit Mix-Ups Are the First Trap

In the same manual, solenoid model codes often use bar while mechanical codes sometimes use MPa. 0.6 MPa is 6 bar. The number looks small and is not. Third-party summary sheets online mix kg, kgf/cm² and bar even more freely.

So on every metering pump selection table, confirm the unit on each column before you compare magnitudes. Cross-comparing numbers across brands or series without checking units is how wrong shortlists get made.

Do Not Skip Head Materials and the Motor Line

Once flow and pressure line up, open the liquid-end material page. PVC, PVDF, PTFE and SS316 each have their own chemical and temperature limits. Sodium hypochlorite and dilute acids often sit on PVC or PVDF. Concentrated sulfuric acid and solvents need a separate check. Hot duty can rule plastic heads out entirely. Reading only the main capacity table is the second common miss.

Motor power and supply matter too. NDWS motors are often 180 W, with three-phase 380 V, single-phase 220 V, and options for VFD or explosion-proof frames. If the plant only has single-phase power, circling a three-phase row wastes a shipment. Control is the same story: a 4–20 mA or pulse input needs the external-control or electric stroke option, not a plain manual stroke pump.

Online Summaries Versus the OEM Metering Pump Selection Table

Web “complete lists” are fine for range: they show roughly where a series sits in flow and pressure. Ordering still goes back to the OEM metering pump selection table, model by model. One mistyped letter on a third-party sheet and you have the wrong material or the wrong power.

A better habit is a small plant sheet of your own: nameplate model, chemical, dosing point and line pressure for each pump in service. When you replace a pump or order spares, you match against that record instead of climbing up to a corroded nameplate. No published parameter chart replaces site duty notes.

Accessories Are Missing From the Main Rows but Not From the Job

NEWDOSE mechanical manuals state plainly that pumps ship without accessories. Discharge side often needs a back pressure valve, pulsation dampener and relief valve. Suction side often needs a strainer or foot valve. A calibration column may belong in the package too. Absence from the main table does not mean you skip them.

When the differential pressure across the pump is under 1 bar, a back pressure valve is nearly standard. Long lines with many bends benefit from a dampener. If someone can close a discharge valve by mistake, fit relief. After you lock the host model on the metering pump selection table, list accessories on a separate line and confirm with the supplier what is included.

Conclusion

Treat the metering pump selection table as a screening tool. Write flow, pressure, chemical and power first. Cut rows that fail pressure, then pick a workable flow, then confirm materials, motor and accessories. Check units before you compare numbers. Use online summaries only for range, and order against the OEM chart. When the duty sheet is complete, reading the table is quick and the model you circle usually fits. If you want a line-by-line check against a specific manual, contact us.

FAQ

1. Is the flow on a metering pump selection table the normal operating flow?

Usually it is the rated maximum. Keep normal duty roughly between 30% and 90% of that rating. Running for long periods at a tiny stroke often hurts accuracy.

2. What if my flow sits between two rows?

Prefer the slightly larger capacity, as long as the pressure column still clears the injection point. Do not trade away pressure just to land on a smaller frame.

3. The chart has no exact flow I need. Now what?

Check the stroke and frequency turndown on neighboring models. Many pumps can run below rating. If coverage is still short, move to another series, a dual-head layout, or a duty/standby pair.

4. Can I match an old nameplate straight into the table?

It is a starting point only. Recheck flow, pressure and chemical. Duties change, and a corroded nameplate should lose to a fresh site measurement.

5. Can I compare solenoid and mechanical pumps on one metering pump selection table?

Do not cross-compare directly. Columns, units and control options differ. Choose the drive type first, then screen inside that family’s chart.