Doseuro FM Pump: Where the Economy Diaphragm Metering Pump Fits

For small dosing duties, most people reach for a solenoid pump first. Some sites, though, want a motor-driven mechanical diaphragm pump because it's simple and tough. Browse the Doseuro range with that in mind and you'll find a small model called FM. The data sheet is direct about it: the Doseuro FM pump is the most economical mechanical diaphragm metering pump in the line.

What Kind of Pump the Doseuro FM Pump Is

FM is a spring return mechanical diaphragm pump with a vertically mounted motor, built as a compact monoblock. It differs from the Type D in two main ways:

• The gearbox casing is reinforced PP, and the literature notes the all-plastic casing suits acid environments.
• The worm gear reducer is grease-lubricated for life, so there's no periodic oil change as on oil-bath pumps.

The diaphragm is PTFE, the standard motor is a 0.09 kW 4-pole unit, and connections are ½" BSP male. Versions with a PP or PVC head ship with an installation kit, so the pump is ready to pipe up out of the box. The literature calls it plug and play.

Flow and Pressure of the Two Doseuro FM Pump Models

There are only two models, and flow is selected by reducer ratio. Figures at 50 Hz:

1. FM050N-30: ratios H, F, D and B give 41, 58, 82 and 116 strokes per minute, for about 4.5, 7, 9.5 and 14 L/h, with 10 bar maximum.
2. FM050N-50: the same four ratios give about 17, 23, 34 and 47 L/h, with 5 bar maximum.

Flow is somewhat higher at 60 Hz. For example, the FM050N-30 on ratio D gives 11.4 L/h. The B ratio is listed only with a 50 Hz figure.

The Doseuro FM pump weighs only 5–5.5 kg, so mounting it next to a tank or on a small bracket is easy.

Low-Flow Duties Where the Doseuro FM Pump Fits

The data sheet lists four applications: fertigation, water treatment, food industry and cooling towers, dosing coagulant, fertilizer, acid and polymer. From our own low-flow dosing work, these are the duties where it makes sense.

Cooling towers and small circulating systems

Antiscalant or biocide dosing up to a dozen or so liters per hour into a low-pressure point sits right in the FM050N-30 range. The plastic casing copes well in damp pump rooms with acid fumes.

Fertigation

Fertilizer and acid dosing that changes with the season can be handled with manual stroke adjustment. The pump is small and easy to move, so one per irrigation zone is practical.

Small water treatment units

Coagulant dosing on packaged water plants or small wastewater stations, at twenty or thirty liters per hour and a few bar, points to the FM050N-50.

Food plant utility systems

Wash water and cooling water systems often need a few liters to a dozen or so liters per hour. These sites are sensitive to leaks. A mechanical diaphragm keeps the liquid separate from the drive, and the literature lists "no leakage allowed" as one of the FM's intended conditions.

Reading a Doseuro FM Pump Code

The FM model code follows the Type D pattern. Take FM050N-50-B-12-DV-TD: FM is the pump type, 050N the size tied to stroke length, 50 the diaphragm diameter code, B the reducer ratio, 12 the material code, and the rest covers valve type and extra information.

The longer order code has a few positions worth noting. Valve type offers double ball only. The installation kit has its own position, either without a kit or with a 20LT or 50LT option. The motor can be single-phase, three-phase or omitted. Break down someone else's model or order code in that order and you'll see the flow range and materials right away.

Installation and Routine Care

Small as it is, the Doseuro FM pump installs like a bigger pump. Keep the tank level above the pump head, keep suction lines short, and fit an inlet strainer so sludge from the tank bottom doesn't jam the check valves. When the injection point has very little pressure, add a back pressure valve on the discharge, or siphoning will push flow well above the dial setting.

Routine care focuses on the diaphragm and check valves. The gearbox is greased for life, so that's one less service task. With chemicals that crystallize, flush the head with clean water before shutdown. It beats taking the valves apart later.

Choosing Materials

The FM data sheet gives four standard wetted materials: 316L stainless, PVC, PP and PVDF. Plastic heads use Pyrex glass balls, PVDF seats and FPM gaskets. The stainless version uses 316L balls and seats. Match them to the chemical and temperature.

One caution. The FM data sheet shows the material codes differently on two pages, 41, 43, 20 and 38 on one and 11, 12, 13, 16 and 23 on another. When ordering, write the material names along with the code and have the factory confirm.

Doseuro FM Pump vs D050N

Both use the 050N size, so they get mixed up. A short comparison:

• Pressure: D050N-30 reaches 14 bar with a metal head; FM050N-30 is 10 bar.
• Lubrication: Type D runs in an oil bath, FM is greased for life.
• Adjustment: Type D can take a 4-20mA, fieldbus or pneumatic actuator. The FM order code lists manual adjustment only.
• Casing: FM uses reinforced PP, better suited to acid fume environments.

So if you need instrument-driven control or more pressure, take the D050N. For fixed manual dosing in a corrosive environment where a simpler build is welcome, the Doseuro FM pump is the better fit.

Limits to Know Before You Buy

The Doseuro FM pump isn't a do-everything pump. It is also meant for duties where high pressure isn't needed, and the FM050N-50 tops out at 5 bar. Adjustment is manual only. You can change stroke running or stopped, but there's no signal input. For proportional dosing or flowmeter pacing, either move to a Type D with an actuator or look at the Doseuro SDP solenoid pump.

Conclusion

Within the Doseuro range, the Doseuro FM pump is the economy option for low flow, low pressure and manual adjustment, with two models covering about 4.5–47 L/h. A plastic casing, grease lubrication and an included installation kit make it a good fit for cooling towers, fertigation and small water treatment duties. For automatic control or more pressure, step up to the D050N or another model.

FAQ

What's the lowest flow on an FM?

At 50 Hz, the FM050N-30 on its lowest ratio gives about 4.5 L/h. Below that, reduce the stroke.

Can a Doseuro FM pump take a 4-20mA signal?

No, adjustment is manual only. For signal control, look at a Type D with an actuator or an SDP solenoid pump.

Does it need oil changes?

No. The FM gearbox is grease-lubricated for life. Routine checks focus on the diaphragm and check valves.

Can it go in a pump room with acid fumes?

Yes. The literature specifically says the all-plastic casing suits acid environments. Keep the motor protected from moisture.

Does it come with installation parts?

FM pumps with PP or PVC heads include an installation kit. Ask separately for stainless and PVDF versions.

If you're weighing a Doseuro FM pump against a Chinese-made solenoid pump for a small dosing job, send flow, pressure and chemical through our contact page.