The Danfoss iSave 21 Plus (code 180F7015) is a seawater reverse-osmosis energy recovery device supplied as a bare unit without an electric motor, combining a rotary pressure exchanger and a booster pump in one assembly. Specify your own motor, coupling and base frame, or ask us for the matching motorised build.
Documentation & Drawings
Technical Specifications
| This Configuration | |
| Code number | 180F7015 |
| Model | iSave 21 Plus |
| Motor | Not included — bare device |
| 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 | — |
| Weight & Footprint | |
| Weight (dry) | 47 kg (103 lb) |
| Identification | |
| Manufacturer | Danfoss High Pressure Pumps |
| Data sheet reference | Danfoss AI243586503158en-000404, §8.1 |
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. 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?
What else do I need to order with this?
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.
