NEWDOSE Mechanical Diaphragm Pump: NDJ vs ND2000 Flow and Pressure

A NEWDOSE mechanical diaphragm pump from the NDJ series covers 40 to 150 L/h, while the ND2000 series covers 500 to 2000 L/h. Both use the same eccentric drive and spring return principle, but the ND2000 adds a cast aluminium housing, a damping slide rod and spring-loaded plate check valves to handle much larger stroke volumes. If your duty sits below 150 L/h, look at NDJ; above 500 L/h, look at ND2000.

This comparison is for engineers and buyers who already have flow and pressure figures. The 150 to 500 L/h band is served by the NDW and ND1000 series, which our NEWDOSE mechanical diaphragm pump selection guide covers. Here we stay with NDJ and ND2000.

How a NEWDOSE mechanical diaphragm pump works

Both series share one operating manual, and the working principle is the same. A motor turns an eccentric shaft. The eccentric offset becomes the straight-line travel of a push rod, and a return spring brings the rod back. When the rod pulls back, the pump head volume grows, pressure drops and the suction check valve opens. When it pushes forward, head pressure rises above line pressure and the discharge valve opens. One full cycle is a stroke, and the travel distance is the stroke length.

Flow is set by turning the stroke adjustment knob, which changes how far the push rod travels. The scale shows stroke length as a percentage of full stroke, and you can read it as a rough percentage of full flow at the current pressure. The manual quotes a steady-state accuracy within ±1% and stepless adjustment from 0 to 100%. Both series use PTFE diaphragms and a grease-lubricated gearbox. Never add grease while the pump is running. For a closer look at the eccentric and push rod, see how a mechanical diaphragm metering pump works.

Where the two series differ in construction

Housing and shaft support

The NDJ eccentric shaft is supported by bearings on both ends rather than overhung, so the geared motor transmits torque without carrying axial load. The pump is compact enough to sit directly on a chemical tank.

The ND2000 uses a high-strength cast aluminium housing that keeps weight down. Its spec sheet describes a motor that drives the eccentric shaft directly with spring return. It also adds a damping slide rod that reduces the pipe shock, vibration and noise caused by idle eccentric travel, which improves flow linearity. With strokes of 8 to 16 mm, that feature earns its place.

Check valves

This difference is easy to miss when comparing NEWDOSE mechanical diaphragm pump quotes. The NDJ uses ball check valves built from a sleeve, body, ball and seat. Do not overtighten them into the head, especially on plastic heads, or the head can crack. The ND2000 uses plate valves with a spring and guide plate, so the valve closes promptly at high flow. Both seal on a face O-ring, so skip PTFE tape.

Stroke control and options

On the NDJ you adjust stroke by hand, even while running. The ND2000 is the NEWDOSE mechanical diaphragm pump to pick for automation: it can be ordered with a 4–20 mA electric stroke actuator, a variable-frequency motor or an explosion-proof motor, which suits DCS or PLC control. The manual does not list these options for NDJ, so confirm with the factory if a small-flow point needs them.

Head materials

NDJ heads come in PVC, PVDF, PTFE and SS316. The ND2000 sheet lists PVC, PTFE and SS316. If a high-flow chemical calls for PVDF, raise it before ordering.

NEWDOSE mechanical diaphragm pump flow and pressure ranges

The NDJ line splits into NDJS and NDJL. NDJS offers 40, 60, 75, 100, 130 and 150 L/h, with rated pressure falling from 10 bar to 3 bar, on a 60 W motor. NDJL offers 70, 80, 105 and 150 L/h at 5 to 10 bar, on a 90 W motor. At 150 L/h, NDJL still gives 5 bar where NDJS gives 3 bar.

The ND2000 offers 500, 700, 1000, 1300, 1600 and 2000 L/h on a 750 W motor. Rated pressure runs 10, 9, 6, 4, 3 and 3 bar respectively.

The pattern holds across every NEWDOSE mechanical diaphragm pump: bigger flow steps carry lower pressure ratings. Line pressure plus a safety margin has to fit inside the rating of the step you choose. Say you need about 1000 L/h into a 5 bar line. The 1000 L/h step is rated 6 bar, which leaves a thin margin, so two 700 L/h pumps in parallel or a higher-pressure pump type is usually the safer call.

Choosing a NEWDOSE mechanical diaphragm pump for your duty

1. Up to 150 L/h: NDJ. Pick NDJL when pressure is on the high side.
2. 500 L/h and above: ND2000, stepping down the table until pressure fits.
3. 150 to 500 L/h: neither; look at NDW or ND1000.
4. Remote stroke control, VFD or explosion-proof motor needed: ND2000 first.
5. Tight space, pump sitting on the tank: NDJ.

A common rule is to size at about 1.3 times maximum demand so normal running sits mid-scale on the stroke dial. Our note on stroke and back pressure margin explains why.

Site issues for any NEWDOSE mechanical diaphragm pump

Nameplate flow is measured on clean water at room temperature, so viscous chemicals typically deliver a little less. The manual suggests calibrating after the first 12 hours at 100%, 50% and 20% stroke. Keep suction lift within 2 m. If the pressure difference between inlet and outlet is under 1 bar, fit a back pressure valve to stop siphoning. The ND2000 moves a large volume per stroke, so long discharge lines generally need a pulsation dampener, with the back pressure valve installed after it.

Service intervals are the same for every NEWDOSE mechanical diaphragm pump in this manual: check grease after the first 2000 running hours, then every 3000 hours or six months, and replace the diaphragm every 5000 hours or yearly. Always isolate power, release line pressure and close both valves before opening the head, and wear gloves and eye protection with corrosive chemicals.

Conclusion

Choosing a NEWDOSE mechanical diaphragm pump between these two series comes down to the flow band first and pressure second. NDJ handles up to 150 L/h with simple manual control; ND2000 handles 500 to 2000 L/h and adds automation and motor options. Check that line pressure plus margin fits the rated step. Browse our mechanical diaphragm pump range or the NEWDOSE brand page, then send us the chemical, maximum dose rate and line pressure and contact our engineers to confirm the model.

FAQ

Can an NDJ pump deliver 200 L/h?

No. The largest NDJ step is 150 L/h. Above that, look at NDW or ND1000 per the selection manual.

What is the highest pressure on the ND2000?

10 bar on the 500 L/h step. The 1600 and 2000 L/h steps are rated 3 bar.

Are NDJ and ND2000 diaphragms interchangeable?

No. NDJ diaphragms are 90 or 105 mm across, ND2000 diaphragms are 155 or 160 mm.

What happens if a NEWDOSE mechanical diaphragm pump return spring weakens?

Flow usually drops and output turns unsteady, because the push rod no longer returns fully. Inspect the spring whenever you change the diaphragm or oil seal.

Is a NEWDOSE mechanical diaphragm pump suitable for replacing an imported pump?

Often, if flow and pressure match a rated step. Our Milton Roy vs NEWDOSE replacement comparison walks through it duty by duty.