ProMinent DUODOS Air-Operated Double Diaphragm Pump: Transfer Without Electricity

Say ProMinent and most people picture a compact solenoid metering pump clicking away beside a chemical tank. The German company also makes a pump with no wiring at all, driven only by compressed air: the ProMinent DUODOS air-operated double diaphragm pump. A customer recently asked whether it would work on a site with a ready air supply but no convenient power, so here is how we explain it.

What Is the ProMinent DUODOS?

The ProMinent DUODOS is a compressed-air double diaphragm pump, and the literature stresses that it has no electrical components. Two diaphragms are pushed by air pressure to draw in and discharge liquid in turn, and the valve balls seat by gravity.

It is self-priming and can run dry safely, so a short spell of running empty won't ruin it. Flow is set by adjusting the supply air pressure. The air control system is designed for oil-free operation, and the air valve must not be lubricated. One more trait: if line back pressure exceeds the air pressure inside the pump, it simply stops, rather than forcing against a closed line the way a motor pump would.

ProMinent DUODOS Models and Specs

The range comes in four sizes, 20, 50, 100 and 200, each in two material versions:

• PPS: PP housing with a Santoprene diaphragm, fluid temperature 10 to 80 ℃;
• PVT: PVDF housing with a PTFE diaphragm, fluid temperature −13 to 93 ℃.

At a 2 bar differential, the four sizes deliver up to roughly 1200, 3000, 6000 and 12000 L/h. Maximum air pressure is 7 bar, fluid viscosity up to 200 mPas, and solids must be smaller than 2 mm.

Take the ProMinent DUODOS 20 from the manual: air supply 1.5 to 7 bar, maximum discharge pressure 7 bar, maximum free flow 20 L/min, dry suction lift about 2 m, wet suction lift up to 7 m once the pump is primed, and a weight of just 1.2 kg. The PPS version uses EPDM seals and a stainless steel pushrod; the PVT version uses PTFE seals and a Hastelloy pushrod.

Not the Same Job as a ProMinent Metering Pump

This distinction matters. A ProMinent metering pump is built for precise dosing, with a steady volume per stroke and signal-based adjustment. ProMinent DUODOS output depends heavily on back pressure, and the manual tells you to read it against the performance curve. It excels at transfer, not dosing measured to the milliliter.

So our usual advice:

1. Unloading drums, emptying totes, and filling a make-up tank with concentrate are good jobs for the ProMinent DUODOS;
2. Proportional dosing into a pipeline still calls for a metering pump, ProMinent or otherwise;
3. The two working together is the most common setup: the air pump refills, the metering pump doses.

The manual lists the maker as ProMinent GmbH of Heidelberg, Germany. The ProMinent DUODOS and the company's metering pumps come from the same company; they simply do different jobs.

Where the ProMinent DUODOS Fits

No electrical parts means less wiring on site, and fewer worries in damp areas that get washed down. If the plant already has a compressed-air network, you just connect an air line.

It's handy for temporary transfers too. Emptying an old drum when changing chemicals or draining a cleaning tank takes an air hose and a few minutes, then you put the pump away, with no electrician needed. Many dosing rooms that run a ProMinent metering pump handle the refill step exactly this way.

Be careful in hazardous areas. The literature only says the pump has no electrical components; it does not state an explosion-proof certification. Projects in classified zones must confirm this with the manufacturer.

Installation and Air Supply Traps

The ProMinent DUODOS must be mounted vertically. Tilt it and the balls won't seat, so nothing comes out. Keep suction lines short with few bends, and don't let fittings reduce the pipe bore. With rigid piping, put a short length of flexible hose between pump and pipe to absorb vibration and strain. A pulsation dampener on the outlet is recommended, plus a relief valve on the discharge line so a closed valve can't overload the pump.

The air supply causes most problems. Air must be oil-free and dry, with a regulator ahead of the pump and pressure no higher than 7 bar. Water in the air can freeze at the exhaust and make the pump misbehave, so fit a dryer. Other equipment switching on and off on the same air network causes big pressure swings, so size the supply generously.

Two more points people miss. If a diaphragm ruptures, chemical comes out of the air exhaust, so route the exhaust to a safe area when pumping toxic fluids. Noise can reach about 88 dB, so plan for it in staffed rooms.

Start-Up and Routine Care

To start, open the air valve 1/2 to 3/4 of a turn. If stroke rate goes up but flow doesn't, that's cavitation. Back the valve off a little, let the chamber fill with liquid, then open it gradually.

Before commissioning a ProMinent DUODOS, torque the 8 housing bolts to 5 Nm in sequence, and recheck once a year, since plastic creeps and the bolts slowly loosen. Flush after every use with fluids that settle or crystallize, and always drain the pump after use when temperatures drop below 0 ℃.

Conclusion

The ProMinent DUODOS sits next to the ProMinent metering pump line as a transfer pump: air driven, no electrical components, ideal where there's an air supply and liquid to move. Choose PPS or PVT by fluid first, then pick a size from 20 to 200, and keep the air oil-free, dry and at no more than 7 bar. Leave precise dosing to a metering pump, and let each pump do its own job.

FAQ

Can the ProMinent DUODOS replace a metering pump for dosing?

We don't recommend it. Its flow shifts noticeably with back pressure, so it's suited to transfer, not accurate dosing. For proportional dosing, use a metering pump.

Which material should I use for sodium hypochlorite?

The literature has no chemical chart, so check the manufacturer's resistance list. PVT, with a PVDF housing and PTFE diaphragm, generally covers more chemicals, but still verify concentration and temperature.

The pump is cycling but nothing comes out. What first?

Check that the suction valve is open, then whether the suction lift is too high or the line and strainer are blocked. Finally, open it up and inspect the balls and seats for wear.

Liquid is coming out of the air exhaust. Why?

On a ProMinent DUODOS that almost always means a ruptured diaphragm. Stop the pump and replace it. With hazardous fluids, the exhaust should already be piped to a safe area.

Can it be installed outdoors?

The manual asks for indoor installation where possible. If it must go outside, protect it from sun, rain and frost, and keep the ambient temperature between −10 and 40 ℃.

If you need to pair an air pump with a metering pump, or want to compare NEWDOSE metering pumps, contact us.