Danfoss APP axial piston pumps and iSave energy recovery devices are the standard pairing in small and medium seawater RO plants: containerised units, marine and offshore systems, resorts and industrial sites. Meliora sources complete APP pumps, iSave units and their service parts for plants across the Gulf.
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In short: Danfoss APP pumps are water-lubricated axial piston pumps covering 0.6 to 92 m³/h at up to 80 bar, and the iSave is a combined pressure exchanger, booster pump and motor covering 6 to 70 m³/h. Meliora sources both, and their spare parts, for SWRO plants. Send the code number and serial number from the nameplate.
A Danfoss APP pump is an axial piston pump: a positive displacement design, where most large desalination pumps are centrifugal. It delivers a constant flow that depends on speed and not on pressure, which makes it efficient at the small flows where a centrifugal pump struggles. The pumped seawater lubricates the pump, so there is no oil system. Danfoss builds the wetted parts from duplex and super duplex stainless steel with carbon-reinforced PEEK.
Danfoss describes the APP range as covering 0.6 to 86 m³/h for small and medium SWRO plants, and its data sheet for the largest frame extends to the APP 92. The figures below are from the Danfoss data sheet for the large-frame pumps.
| Model | Flow at maximum speed | Maximum outlet pressure |
|---|---|---|
| APP 53 | 53 m³/h (235 gpm) | 80 barg |
| APP 65 | 68 m³/h (299 gpm) | 80 barg |
| APP 78 | 78 m³/h (345 gpm) | 80 barg |
| APP 86 | 88 m³/h (387 gpm) at 1,700 rpm | 70 barg |
| APP 92 | 92 m³/h (405 gpm) at 1,780 rpm | 70 barg |
Source: Danfoss data sheet, APP 53–92. Smaller frames cover the lower flows down to 0.6 m³/h. Always confirm limits against the data sheet for your model.
Two figures from the same data sheet matter for anyone maintaining these pumps. The inlet water must be filtered to 10 micron absolute, and Danfoss gives a service interval of 8,000 operating hours before inspection. The filtration figure matters because the pump relies on a film of the pumped water between its moving parts, and particles in that water wear them.
The iSave combines three things in one unit: a rotary isobaric pressure exchanger, a high-pressure booster pump and an electric motor. In a plant with a separate pressure exchanger these are three pieces of equipment. Danfoss states an efficiency of up to 92% and a service interval of at least two years within the specified operating limits.
| Model | Flow range | Maximum outlet pressure | Speed range |
|---|---|---|---|
| iSave 21 Plus | 6–22 m³/h (26–96 gpm) | 83 barg | 500–1,500 rpm |
| iSave 40 | 21–41 m³/h (92–181 gpm) | 83 barg | 600–1,200 rpm |
| iSave 50 | 42–52 m³/h (184–228 gpm) | 83 barg | 525–650 rpm |
| iSave 70 | 50–70 m³/h (220–308 gpm) | 70 barg | 625–875 rpm |
Source: Danfoss SWRO product overview. Maximum differential pressure across the iSave is 5 barg for all four models.
For some repairs Danfoss supplies the part, and for others it supplies only a complete pump or a factory repair. We ask Danfoss which applies to your model and serial number, and quote what they confirm.
APP pumps and iSaves are sized for plants that produce from a few cubic metres to a few thousand cubic metres of water a day. In the Gulf that means resort and hotel plants, labour camps, offshore platforms and vessels, industrial process water plants and containerised units that can be moved between sites. Larger plants use several pumps in parallel, which gives them built-in redundancy: one pump can be taken out for service while the others run.
Plants at this scale often have no spare pump on the shelf, so a failed high-pressure pump stops water production the same day.
APP pump or iSave out of service? Send the nameplate details. Plant-down enquiries get a reply within 4 hours, standard quotations within 48 hours.
Page reviewed October 2026 · Meliora FZCO, Dubai Silicon Oasis, UAE
A Danfoss APP pump is a high-pressure axial piston pump designed for seawater reverse osmosis. It is a positive displacement pump lubricated by the water it pumps, built from duplex and super duplex stainless steel and carbon-reinforced PEEK, with a range of 0.6 to 92 cubic metres per hour.
The Danfoss data sheet for the APP 53 to APP 92 gives a service interval of 8,000 operating hours before inspection, provided the pump runs within its specified limits and the inlet water is filtered to 10 micron absolute.
An iSave combines a rotary isobaric pressure exchanger with a booster pump and an electric motor in one unit. A stand-alone pressure exchanger, such as an Energy Recovery PX, needs a separate booster pump. The iSave covers 6 to 70 cubic metres per hour, which suits small and medium plants.
Danfoss lists four: iSave 21 Plus for 6 to 22 cubic metres per hour, iSave 40 for 21 to 41, iSave 50 for 42 to 52 and iSave 70 for 50 to 70. The first three are rated to 83 barg outlet pressure and the iSave 70 to 70 barg.
The model, code number and serial number from the nameplate, the part required and the quantity. A photo of the nameplate is enough if the numbers are unclear.