Mechanical Diaphragm Pump Selection: Choosing Between NEWDOSE NDJ, NDW, ND1000 and ND2000
Once the dose passes a few tens of liters per hour, a solenoid pump starts to struggle and you are usually looking at a mechanical diaphragm pump. The catch is that NEWDOSE has five standard mechanical series, and their flow ranges overlap. At 500 L/h, both the NDWL and the ND2000 can do the job. So at this stage you can't select on the flow column alone. Pressure, motor, lubrication and materials all count.
Split the Five Series by Flow First
We usually break the NEWDOSE mechanical diaphragm pump data sheet into three rough bands:
- Up to 150 L/h: the NDJ series. NDJS covers 40–150 L/h at 3–10 bar with a 60 W motor. NDJL covers 70–150 L/h at 5–10 bar with a 90 W motor.
- 8–530 L/h: the NDW series. NDWS covers 8–386 L/h at up to 16 bar with a 180 W motor. NDWL covers 275–530 L/h at 4.5–7 bar with a 370 W motor.
- 500–2000 L/h: ND1000 runs 660–1200 L/h at 3–5 bar. ND2000 runs 500–2000 L/h at 3–10 bar. Both use 750 W motors.
The largest single mechanical diaphragm pump in the range is the ND2000-2000/0.3, at 2000 L/h and 3 bar. Above 2000 L/h one pump is not enough, so plan several in parallel or ask the factory to size it.
Overlap between bands is normal, and pressure settles it. Say you need 500 L/h at 8 bar. NDWL tops out at 7 bar and ND1000 is lower still, which leaves only the ND2000-500/1.0. Plenty of people get stuck here. Rule out by pressure first and very few options remain.
Structural Differences in Each Mechanical Diaphragm Pump Series
NDJ: sits right on the tank
This compact mechanical diaphragm pump has an eccentric shaft with bearings front and back, so the gear motor only transmits torque and carries no axial load. The gearbox is grease-lubricated and light enough to mount straight on a dosing tank, which saves a pump stand. It is a natural fit for compact packaged dosing skids.
NDWS and NDWL: aluminum housing with worm gear
Both use a die-cast aluminum housing and a worm gear drive. The factory says this lets them run a smaller motor for the same flow and pressure. The low-flow NDWS models reach 16 bar, the highest pressure among these series. These two run on oil: change it after the first 800 operating hours, then every 3000 hours or six months.
ND1000 and ND2000: the choice above 1000 L/h
The ND2000 has a cast aluminum housing with the motor driving the eccentric shaft directly, plus a damped slide rod for smoother running, at 200 SPM. Pressure falls as flow rises: 10 bar at 500 L/h, 6 bar at 1000 L/h, and only 3–4 bar from 1300 L/h up. The ND1000 runs at 118 to 177 SPM and 3–5 bar.
If you need a mechanical diaphragm pump for more than 1000 L/h and above 5 bar, only the ND2000-1000/0.6 qualifies. Any higher and you split the duty across two pumps.
Don't Pick One Pump Head Material for Everything
NDJ, NDWS and NDWL offer PVC, PVDF, PTFE and SS316 heads. The ND1000 and ND2000 literature lists only PVC, PTFE and SS316, with no PVDF. On a high-flow project where you planned on PVDF, confirm with the factory early or switch to PTFE.
Every series uses a modified PTFE diaphragm, so that part needs no debate. The real work in choosing a mechanical diaphragm pump is the head and valve set. Put the chemical name, concentration and temperature on the inquiry together.
Don't Size Too Tight or Too Loose
Flow on a mechanical diaphragm pump is set by stroke length. The scale on the adjuster shows stroke as a percentage of full stroke, which you can treat as roughly a percentage of flow. A pump running for long periods at very short stroke loses accuracy and stability, so we aim for the normal duty to sit in the middle to upper part of the range and add about 20% headroom on the maximum dose.
After installation, calibrate at full stroke, half stroke and 20% stroke, as the manual recommends. Write down the measured flows, draw them as a line and post it next to the pump. Operators then have something to go by instead of turning the handwheel by feel.
Filling In the Mechanical Diaphragm Pump Selection Code
The NEWDOSE selection code has six blocks: series, flow, pressure (in MPa), pump head materials, power supply and adjustment method. The manual's example is NDWL-410-0.6-PVT-A-I: NDWL series, 410 L/h, 0.6 MPa, PVC head, 380 V three-phase standard motor, electric stroke adjustment.
Don't skip the supply block. A is a 380 V three-phase standard motor, AVF a variable-frequency motor, AEX an explosion-proof motor and B is 220 V. For adjustment, H is manual and I is an electric stroke actuator that accepts 4–20 mA. If the site is a chemical or fuel area that needs explosion protection, specify AEX from the start. Swapping the motor later is a headache.
Quote the Accessories With the Mechanical Diaphragm Pump
In the manual's installation drawing, the discharge side carries a safety valve, pulsation dampener, back-pressure valve and diaphragm pressure gauge, in that order. The suction side has a Y-strainer, with a calibration column alongside. The manual also states that a back-pressure valve is required when the pressure difference between suction and discharge is under 1 bar, or the dosing won't be accurate.
On a high-flow mechanical diaphragm pump with long, narrow discharge lines, put the back-pressure valve near the injection point, and downstream of the dampener if there is one.
Place a drip tray under the pump head. If chemical drips from the head's leak detection port, the diaphragm has failed. If it's oil, the oil seal has gone. Replace oil seals yearly per the manual, and buy spares with the pump to keep downtime short.
Conclusion
Selecting a NEWDOSE mechanical diaphragm pump comes down to four steps: band it by flow, rule out series by pressure, check that your head material is offered for that series, then write the supply and adjustment method into the code. Under 150 L/h, start with NDJ and NDWS. For a few hundred liters, look at NDWL and ND2000. Above 1000 L/h, it's ND1000 and ND2000, and past 2000 L/h, run pumps in parallel. Order the accessories per the installation drawing and commissioning gets much easier.
FAQ
NDJ or NDWS at 120 L/h?
It depends on pressure and mounting. The NDWS-120/0.7 is rated 7 bar. The NDJ models that reach 120 L/h are all 5 bar. If 5 bar is enough and you want it on the tank, NDJ is more convenient.
Can I adjust a mechanical diaphragm pump with a VFD?
A variable-frequency motor is available. The factory literature, though, prefers the electric stroke actuator, which changes stroke length directly and includes error compensation, avoiding some of the drawbacks of relying on speed alone.
Can oil and grease be mixed?
No. NDJ and ND2000 use grease, while NDW and ND1000 use oil. Stick with the lubricant supplied by the factory. Anything else lowers drive efficiency and can affect the warranty.
What should I do on a cold start in winter?
Set stroke to 0% and run unloaded for about 5 minutes so the lubricant warms up, then bring the stroke up gradually. Below 0 ℃, oil-lubricated series need winter-grade oil.
Can one mechanical diaphragm pump feed two dosing points?
We don't recommend it. The manual notes that even a small pressure difference between points sends the chemical toward the lowest-pressure point, so the split is hard to keep even.
To match a specific model to your flow and pressure, put your duty data together and send it through our contact page. We'll check it against the data sheet with you.