HND High-Pressure Diaphragm Pump: Specs, Best Applications and Limits
When the injection point runs at well over ten bar, most engineers reach for a hydraulic diaphragm pump. That works, but the oil circuit, refill valve and diaphragm chamber all need looking after, and the price is noticeably higher. The NEWDOSE HND takes a different route: a mechanically actuated high-pressure diaphragm pump that reaches 30 bar. Here is what the data sheet says, which duties it suits, and where you shouldn't push it.
How the HND Differs From a Standard Mechanical Pump
Structurally this high-pressure diaphragm pump is still a mechanically driven diaphragm with spring return, the same principle as the NDW series. The difference is the diaphragm assembly. The HND pairs a modified PTFE diaphragm with a dedicated diaphragm support assembly, which lifts pressure from the usual few bar to 12–30 bar.
There is no hydraulic oil chamber, so none of the refilling and bleeding work that comes with hydraulic pumps. The drive has a damped slide rod, so it runs smoothly and quietly. The factory is clear about the intent: replace some low-pressure hydraulic diaphragm pumps and cut the upfront cost.
High-Pressure Diaphragm Pump Specs, Model by Model
The HND high-pressure diaphragm pump comes in five models, split into two groups.
High pressure, low flow: 47/3.0 and 70/2.0
The HND-47/3.0 delivers 47 L/h at 30 bar, with a 4 mm stroke, 118 strokes per minute and about 6.6 mL per stroke. The HND-70/2.0 delivers 70 L/h at 20 bar with the same stroke, running faster at 177 strokes. Both use a 90 mm diaphragm and a 370 W motor.
These two suit high pressure with modest volume. Note that their stroke volume is identical. The 70 delivers more only because it runs faster.
Medium pressure, more flow: 115, 135 and 160
The HND-115/1.8 delivers 115 L/h at 18 bar, the HND-135/1.6 gives 135 L/h at 16 bar, and the HND-160/1.2 gives 160 L/h at 12 bar. All three use a 105 mm diaphragm, run at 118 strokes per minute with a 550 W motor, and stroke length steps up from 6 mm to 8 mm.
The pattern in this group is plain: as flow goes up, pressure comes down. So with any high-pressure diaphragm pump, confirm the maximum injection pressure before you choose on flow.
A worked example. The injection point peaks at 14 bar and the maximum dose is about 100 L/h. Both the 18 bar HND-115/1.8 and the 16 bar HND-135/1.6 have enough pressure. The 115 leaves roughly 15% flow margin and more pressure margin, so we would normally start there. If the dose may grow later, look at the 135.
The stroke volume column is useful too. Multiply it by stroke rate and you get theoretical flow. If a calibration on site comes out far below that, a check valve not seating or an air leak on the suction line is the usual cause. Check those two first.
Where This High-Pressure Diaphragm Pump Fits
The manual lists petrochemical, natural gas production, refining, thermal power, industrial boilers and pharmaceutical. In practice, we see the best fit in these spots:
- Boiler feedwater or steam drum dosing where the injection point sits in the teens of bar;
- Injecting antiscalant or corrosion inhibitor into pressurized process lines;
- Retrofits of older systems running low-pressure hydraulic pumps that nobody has time to maintain.
Viscous chemicals are another case worth a look. The HND can take check valves with a PTFE elastic element that returns the valve without relying on gravity, which keeps output and linearity steadier with thicker fluids and adds a little back pressure at the discharge.
When Not to Use the HND High-Pressure Diaphragm Pump
The pump head is SS316 only. The literature lists stainless steel as the only wetted material. For anything that attacks stainless, including chloride-bearing chemicals like hydrochloric acid and sodium hypochlorite, it is generally not recommended.
Flow tops out at 160 L/h. Beyond that you need a different series or a hydraulic diaphragm pump.
Above 30 bar you are outside what a mechanical high-pressure diaphragm pump can do, so look at hydraulic diaphragm or plunger pumps.
Poor suction conditions will also defeat it. The manual's troubleshooting table says to keep suction lift within 2 m, and ideally mount the pump below the tank level so chemical floods the head. Discharge pressure is worthless if the suction side can't fill. Ambient temperature should stay between 0 and 45 ℃, and keep the pump and lines out of direct sun.
Installation and Maintenance Points
Every high-pressure diaphragm pump needs a safety valve on the discharge, placed between the pump and the nearest shutoff valve. Route the relief line back to the tank or to drain, and keep its outlet visible so a leaking relief valve gets noticed. Starting the pump with the discharge valve closed spikes the pressure instantly, and it is the most common cause of incidents on high-pressure systems.
Like the NDW series, this high-pressure diaphragm pump runs on oil. Change it after the first 800 hours, then every 3000 hours or six months, and replace the oil seal yearly. Below 0 ℃, switch to winter-grade oil and run the pump at zero stroke for about 5 minutes before loading it.
For remote flow control, fit the electric stroke actuator. In manual mode it shows the current stroke length, and in auto mode it follows a 4–20 mA signal.
Conclusion
The HND brings a mechanical high-pressure diaphragm pump into the 12–30 bar range, with 47–160 L/h of flow and an SS316 head. It suits boiler dosing, injection into pressurized lines and replacing some low-pressure hydraulic diaphragm pumps. Fix the maximum pressure first, then choose flow from the data sheet. Make sure the chemical is compatible with stainless steel and stay inside the published flow and pressure. Get the safety valve and lubrication right and it is an easy pump to live with.
FAQ
Can the HND fully replace a hydraulic diaphragm pump?
No. It covers low-pressure hydraulic duties within 30 bar and 160 L/h. Higher pressure or flow still calls for a hydraulic diaphragm pump.
Can I get a PVC or PTFE head on this high-pressure diaphragm pump?
The current literature lists only SS316 for the HND. If your chemical doesn't suit stainless, ask the factory whether a special build exists rather than modifying it yourself.
Is 30 bar a continuous rating for this high-pressure diaphragm pump?
30 bar is the rated pressure of the HND-47/3.0. In practice, keep working pressure below the rating to leave a margin, rather than running at the limit for long periods.
Can stroke length be adjusted while running?
Yes, by hand. With the electric stroke actuator it can also follow a 4–20 mA signal and display the current stroke length on its panel.
What should I watch when changing the diaphragm?
Isolate power, release discharge pressure, drain the pump head and flush with clean water if needed. Follow the manual for the disassembly order and head bolt tightening, and wear proper protection with toxic media.
If your injection point sits somewhere between the teens and 30 bar, send us the chemical, flow and pressure via our contact page and we'll work out together whether the HND fits.