The Danfoss iSave 21 Plus (code 180F7017) is a complete seawater reverse-osmosis energy recovery unit supplied on a horizontal or vertical base frame with a IEC 132 M 7.5 kW (10 HP), 4-pole motor. It combines a rotary pressure exchanger and a booster pump in one assembly, recovering pressure energy from the membrane reject stream and returning it to the feed — typically cutting SWRO energy consumption by around 60% against a system with no energy recovery.
Documentation & Drawings
Technical Specifications
| This Configuration | |
| Code number | 180F7017 |
| Model | iSave 21 Plus — horizontal or vertical base frame |
| Motor | IEC 132 M, 7.5 kW (10 HP), 4-pole |
| Performance | |
| Geometric displacement | 273 cm³/rev (16.7 in³/rev) |
| HP outlet flow range at max. differential pressure | 6 – 22 m³/h (26 – 96 gpm) |
| LP inlet max. flow | 33 m³/h (145 gpm) |
| Lubrication flow at 60 barg (871 psig), max. | 0.4 m³/h (1.8 gpm) |
| Speed range | 500 – 1500 rpm |
| HP max. outlet pressure | 83 barg (1200 psig) |
| HP min. inlet pressure | 15 barg (217 psig) |
| HP max. inlet pressure | 83 barg (1200 psig) |
| HP inlet min. pressure, intermittent | 3 barg (44 psig) |
| Max. differential pressure (HP in − HP out) | 5 bar (72.5 psi) |
| LP inlet max. pressure | 5 barg (72 psig) |
| LP inlet max. pressure, intermittent | 10 barg (145 psig) |
| LP outlet min. pressure | 1 barg (14.5 psig) |
| LP differential (in − out) at HP max. flow | 0.9 bar (13 psi) |
| Torque at max. differential pressure | 49 Nm (36 lbf-ft) |
| Max. starting torque (stick/slip) | 50 Nm (37 lbf-ft) |
| Operating Conditions | |
| Media temperature | 2 – 40°C (36 – 122°F) |
| Ambient temperature | 0 – 50°C (32 – 104°F) |
| Filtration requirement (nominal) | 5 micron melt-blown, 85% efficient |
| Salinity increase at membrane (40% recovery) | 2 – 3% |
| Sound pressure level LPA at 1 m | 79 dB(A) |
| Motor | |
| Motor size | 7.5 kW (10 HP) |
| Frame size | IEC 132 M |
| Poles | 4 |
| Nominal speed | 1450 rpm |
| Speed range | 500 – 1500 rpm |
| Rated current | 15.2 A at 400 V |
| Rated motor torque at nominal speed | 49 Nm (36 lbf-ft) |
| Motor torque at min. speed | 36 Nm (27 lbf-ft) |
| Motor ambient temperature, max. | 40°C (104°F) |
| Motor insulation class | B |
| Motor degrees of protection | IP 55 |
| Weight & Footprint | |
| Weight (dry) | 116 kg (255 lb) |
| Footprint (horizontal or vertical) | 0.32 m² (3.45 ft²) |
| Identification | |
| Manufacturer | Danfoss High Pressure Pumps |
| Data sheet reference | Danfoss AI243586503158en-000404, §8.2 |
Videos
Optimizing SWRO energy use with Danfoss pumps and iSave ERD selection tools
Understanding SWRO energy use — how to cut it with Danfoss pumps and ERDs
Videos courtesy of Danfoss High Pressure Pumps.
Case Studies
Real installations using Danfoss pumps and iSave energy recovery:
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How the iSave Works
The iSave combines a rotary pressure exchanger, which transfers pressure energy directly from the high-pressure reject brine to the incoming low-pressure feed, with a booster pump that makes up the small pressure differential across the exchanger, both driven by the motor on a common shaft. Because the energy transfer is direct hydraulic displacement rather than a mechanical conversion, the high-pressure feed pump only has to supply the permeate flow.
The iSave 21 Plus delivers up to 22 m³/h (96 gpm) at the high-pressure outlet. All wetted parts are made of high corrosion-resistant materials including Super Duplex stainless steel, and there is no high-pressure mechanical seal and no need for high-pressure flow meters.
Frequently Asked Questions
How do I size the iSave 21 Plus for my plant?
What pre-filtration does it need?
Does it need a separate booster pump?
Does it need a VFD?
How is it shipped?
Specifications reproduced from Danfoss data sheet AI243586503158en-000404. iSave® is a registered trademark of Danfoss A/S. Danfoss reserves the right to alter specifications without notice; confirm critical values against the current data sheet before purchase.
