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Energy Recovery Devices Type iSave

Energy Recovery Devices Type iSave

Danfoss has introduced two reverse osmosis energy recovery devices.

The iSave 21 with a brine flow of 7-21 m3/h and the iSave 40 with a brine flow of 22-40 m3/h are available now. More sizes are under development.

The Danfoss iSave consists of an isobaric pressure exchanger (PE), a high pressure positive displacement booster pump (BP) and an electric motor.
The isobaric pressure exchangers are based on the technology used in the Danfoss APP pumps, and the high-pressure booster pumps are based on the vane pump principle enabling a very light and compact design. The design of iSave 21-40 ensures lubrication of the moving parts by the fluid itself.
All parts included in the iSave 21-40 are designed to provide long service life with a constant high efficiency and minimum service required.
The vane pumps are fixed displacement pumps in which the flow is proportional to the number of revolutions of the driving shaft – enabling flow control.
The electric motor provides speed control of both the pressure exchanger and the high pressure booster pump on the same shaft – preventing over spin / over flushing.
The iSaves need a VFD that allows the motor to apply a constant torque from low speed to maximum speed.

For the complete range of Danfoss iSave Devices go to our dedicated website: High Pressure Water Equipment - iSave Devices


Operating Conditions    
 iSave 21iSave 40
Code number 180F7000 (US 180F7010) 180F7001 (US 180F7011)180F7003
Energy Recovery Device iSave 21 iSave 40
Rated flow  21 m3/hr 41.4 m3/hr *1
Geometric displacement 265.8 cm3/rpm(16.2 in3/rpm) 626 cm3/rpm(38.2 in3/rpm)
High-pressure inlet flow, maximum 21 m3/hr (92.4 gpm) 44 m3/hr (194 gpm)
Low-pressure inlet flow, maximum 33 m3/hr (145 gpm) 67 m3/hr (295 gpm)
High-pressure inlet pressure,maximum 83 bar (1200 psig) 83 bar (1200 psig)
High-pressure inlet pressure,minimum 10 bar (145 psig) 10 bar (145 psig)
High-pressure inlet pressure,intermittent, minimum *3 3 bar (43.5 psig) *2 3 bar (43.5 psig)
Low-pressure inlet pressure, maximum *3 10 bar (145 psig) 10 bar (145 psig)
Low-pressure outlet pressure,minimum 1 bar (14.5 psig) 1 bar (14.5 psig)
High-pressure outlet pressure,maximum 83 bar (1,200 psig) 83 bar (1,200 psig)
Filtration requirements (nominal) *4 3 ìm melt-blown 3 ìm melt-blown
Torque, maximum *5 36 Nm (26.5 lbf-ft) 119 Nm (87.8 lbf-ft)
Starting torque (slip/stick)  - 85 Nm (62.7 lbf)
Power req. at 60 bar, and booster pressure of 3 bar 5.5 kW (7.5 hp) 10 kW (15 hp)
Weight including electric motor 95 kg (209,5 lb) 254 kg (560 lb)
 iSave 21iSave 40
Peak eff. inc. high-pressure booster pump at 60 bar 93% 91%
Maximum pressure raise on iSave *7 3 bar (43.5 psig) 5 bar (72.5 psig)
Maximum low-pressure differential(LP In - LP Out) *7 0.9 bar (13 psi) at 21m3/hr(92.4 gpm) 1.2 bar (17.5 psi) at 40 m3/hr(176.1 gpm)
Maximum lubrication flow at 60 bar 0.42 m3/hr (1.8 gpm) 0.8 m3/hr (3.5 gpm)
Minimum speed 500 rpm 600 rpm
Maximum speed 1,500 rpm 1,200 rpm
Salinity increase at membrane at 40% recovery rate 2-3 % 2-3 %
Typical noise level *6 86 dB(A) 88 dB(A)
*1 Typical average flow at 60 bar
*2 Minimum inlet high pressure can be 1 bar, if speed of iSave is maximum 750 rpm
*3 Intermittent pressure is acceptable for less than 10 minutes within a period of 6 hours
*4 Please see section 7 of datasheet - Filtration
*5 Warning: A minimum of 10 seconds is required when ramping up the speed from zero to maximum. Otherwise, the torque will exceed the maximum limit and may be harmful to the isave.
*6 Noise level is depending on system design. The noise level can be obtained by “proper” design. Please contact M & M Controls.
*7 At speed above 50Hz and power supply lover than 400V the maximum pressure raise is 4 bar.
Electric Motor    
DescriptioniSave 21iSave 40
Motor size kW/HP 5.5/7.5 11/15
Frame size IEC 132S-4P IEC 160L-6P
Speed at 50/60 Hz 1440/1728 970/1165
Efficiency 89% 90%
Rated current (A) 10.7 22
Insulation according to DIN-IEC 34 Class F Class F
Ambient temperature 40oC, 1000m above sea level Class B Class B
Degrees of protection IP55 IP55
Standard coating according to IEC 60721-2-1 Yes Yes Yes
The iSave can also be delivered with a marine motor, an ATEX motor or any other special motor.
Please contact M & M Controls for further information.
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Please call +44 (0)1772 699 999 or email for current price.