Danfoss iSave 21 User manual

isave.danfoss.com
Installation, Operation and Maintenance Manual
iSave 21
521B1174 / DKCFN.PS.003.A1.02
User manual

User manual iSave 21
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180R9221 / 521B1174 / DKCFN.PS.003.A1.02
Document information
and copyright
Validity
Installation, Operation and Maintenance Manual.
Original operating manual document.
Danfoss can accept no responsibility for possible errors in the manual and instructions.
Danfoss reserves the right to alter its products without notice. This also applies to products
already on order provided that such alterations can be made without subsequential chan-
ges being necessary in specications already agreed.
All rights reserved. Contents provided herein must neither be distributed, copied, repro-
duced, edited or processed for any other purpose, nor otherwise translated or published
without Danfoss’express written consent.
This manual is valid for iSaves with:
1. Code no 180F7000
Serial no 2.
From week 145 year 2011
2. Code no 180F7001
Serial no 2.
From week 14 year 2011

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Table of contents 1 CE Declaration of conformity 5
2 Introduction 6
2.1 General 6
2.2 Target group 6
2.3 Symbols 6
2.4 Manufacturer and customer service adress 7
2.5 Additional technical documents 7
3 Safety 8
3.1 General 8
3.2 Intended use 9
3.3 Application range 9
3.4 Preferred system design 10
4 Arrival inspection, handling and storage 10
4.1 Arrival inspection 10
4.2 Return to the supplier 10
4.3 Handling 10
4.3.1 Centre of mass 11
4.4 Storage 12
4.5 Outdoor storage 12
5 Technical data and design review 13
5.1 Design details 13
5.2 Sound level of the iSave 13
5.3 Materials 14
5.4 Temperature and corrosion 14
5.5 Dimensions and weights 14
5.6 Electrical motor data 14
5.7 How does the iSave work? 15
5.7.1 Pressure excharger function 15
5.7.2 Booster pump 16
5.7.3 Lubrication ow 16
5.7.4 Mixing 16
5.7.5 How does the iSave work in an RO system? 16
5.8 Seawater quality 17
5.8.1 Pre-ltration 17
5.8.2 Air bubbles 18
5.8.3 Chemicals 18
5.9 Initial start up and ushing 18
5.10 Initial start up and settings of safety equipment 18
5.11 Flushing 19
5.12 CIP of Membrane cleaning 19
5.13 High pressure remains after shutdown 19
5.14 Over-pressurisation caused by low pressure isolation 20
5.15 Over-pressurisation caused by the high pressure pump 20
5.16 Preferred system design and P&ID 21

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6 On-site installation 22
6.1 General 22
6.2 Installation and alignment 22
6.3 Orientation 22
6.4 Piping and joints 23
6.5 Flexible couplings and exible hoses 24
6.6 Mounting of coupling 24
6.7 Mounting of bell housing on iSave 24
6.8 Accessibility 25
6.9 Drives 25
6.9.1 Electric motor 25
6.9.2 Speed control 25
6.9.3 Starting torque on the iSave/ramping the electric motor 25
6.9.4 Torque overloads protection on the iSave 25
7 Commissioning, start-up and shutdown 26
7.1 Safety regulations 26
7.2 Support 26
7.3 Commisioning 26
8 Service/Maintenance 27
8.1 Safety regulations 27
8.2 Support 27
8.3 Maintenance schedule 27
8.4 Tool used 28
9 Trouble-shooting 29
9.1 Safety regulations 29
10 Appendix 30
10.1 Start and stop procedures (180R9213) 31
10.2 Membrane cleaning of the RO system with iSave unit (180R9214) 37
10.3 Datasheet (521B1116) 43
10.4 iSave part list (180R9209) 59
10.5 iSave overload protection (180R9222) 71
10.6 Hose assembly and installation (180R9084) 81
10.7 Service instructions - assembly and disassembly (180R9219) 85
10.8 Operating- and maintenance instruction, electric motor (180R9163) 103

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1. CE Declaration of conformity

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2. Introduction
2.1 General
iSave is manufactured by Danfoss A/S, and is sold and marketed by a net of authorised
distributors world wide.
This manual contains the necessary instructions for the installation, operation and service of
the iSave.
All personnel who are responsible for the operation and maintenance of the iSave unit
must read and fully understand these instructions, especially the section “Safety” before:
• Transporting of the iSave unit.
• Lifting the unit.
• Installing the iSave unit on a frame.
• Connecting the iSave unit to the uid system.
• Connecting the electrical motor and instrumentation.
• Commissioning the unit.
• Servicing the iSave unit, mechanics and electrics.
• Decommissioning the iSave unit.
Ensure that these instructions are always readily available to all personnel concerned.
2.2 Target group
This manual is intended for use by personnel with qualied training and experience in the
operation and maintenance of a Sea Water Reverse Osmosis (SWRO) or Brackish Water
Reverse Osmosis (BWRO) system.
2.3 Symbols
NB! Indicates something to be noted by the reader
Indicates a situation which will or could result in damage to the iSave and its
function
Indicates a situation which will or could result in personal injury and/or damage
to the iSave
Electrical hazard. Indicates a high-voltage warning
Safety glasses required
Hearing protection required
Safety shoes required
Safety helmet required

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2.4 Manufacturer and customer service adress
Danfoss A/S
DK-6430 Nordborg,
Denmark
Telephone: [phone]
Email: [e-mail]
Home page: www.ro-solutions.com
2.5 Additional technical documents
See also appendix 10
Document name Content
Datasheet Description of the technical data and
dimensions of the iSave
iSave partlist Sectional drawings, parts list and spare part
numbers.
Instruction:
start and stop of the SWRO with iSave unit
Description of how to start and stop the
iSave in the preferred RO system set-up.
Instruction:
Membrane cleaning of RO system with
iSave unit
Description of how to clean the membranes
in the preferred RO system set-up.
Instruction:
iSave overload protection
Electrical wiring diagram on how to protect
the iSave against overload.
Mechanical overload protection of the iSave
Instruction:
Hose assembly and installation
Guideline for Hose assembly and
installation
Service instructions
Assembly and disassembly
Description of how to assembly and disas-
sembly the iSave
Operating and maintenance instructions,
electric motor
Operating and maintenance instructions for
the standard electric motor, delivered from
Danfoss.

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3. Safety
3.1 General
The iSave must not be used for other purposes than those recommended and specied
without rst consulting your local iSave distributor.
This manual must be read and completely understood by the responsible specialist person-
nel prior to installation and commissioning.
Use of this manual does not relieve operation and maintenance personnel of the responsi-
bility of applying normal good judgment in the operation and care of this product and its
components.
This manual must be available to all personnel concerned at the site at all time.
An iSave must always be installed and used in accordance with existing national and local
sanitary and safety regulations and laws. It is the responsibility of the safety ocer or the
chief operator to assure compliance with all local regulations that are not taken into account
in this manual.
The iSave is a rotating machine that typically operates at high pressure.
Always wear suitable safety and lifting equipment when handling the iSave.
• Bolt the iSave properly to the base before start-up to avoid personal injury and/or
damage to the iSave.
• The pipe connections to the iSave must be stress-free mounted, securely fastened to the
iSave and well supported. Improper installation will or could result in personal injury
and/or damage to the iSave.
• Proper installation and care of shutdown devices and over-pressure protection
equipment is essential.
• All electrical installation work must be carried out by authorised personnel in
accordance with EN60204-1 and/or local regulations.
• Install a lockable circuit breaker to avoid inadvertent starting. Protect the motor and
other electrical equipment from overloads with suitable equipment.
• The electric motors must be supplied with adequate cooling ventilation.
• Improper installation can cause fatal injuries.
• The iSave must not operate outside the application range.
• During the initial start-up, slowly raise the pressure of the system and adjust the over-
pressure protection equipment for proper limit settings.
• Make sure that the pressure is released from the iSave before the iSave is discon-
nected from any pipe or hose connections in the iSave.
• Make sure that the iSave can be drained without injuring anyone and without
contaminating nearby equipment or the environment.
• Before intervening in the iSave/system, the power must be shut o and the starting
device must be locked. When intervening in the iSave unit, follow the instructions for
Service/Maintenance, chapter 8.
• A failure to follow the instructions can result in personal injury and/or damage to the
iSave. It will also invalidate the warranty.
• The iSave must never run dry. Dry running produces heat and will cause damage to
internal parts.
• If the iSave does not function satisfactorily, contact your local iSave distributor.
Use of this manual does not relieve operation and maintenance personnel of the
responsibility of applying normal good judgment in the operation and care of this
product.
Electrical
hazard
NB!

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3.2 Intended use
The iSave is designed for use as energy recovery device in Sea Water Reverse Osmosis
(SWRO) or Brackish Water Reverse Osmosis (BWRO) system.
The iSave must not be used for other purposes than recommended and quoted for without
consulting your local iSave distributor.
3.3 Application range
The iSave should only be used within the following limits:
High-pressure inlet ow, maximum 21 m3/hr (92.4 gpm)
Low-pressure inlet ow, maximum 33 m3/hr (145 gpm)
High-pressure inlet pressure, maximum 83 Bar (1200 psig)
High-pressure inlet pressure, minimum 10 Bar (145 psig)
High-pressure inlet pressure, intermittent,
minimum
3 Bar (43.5 psig)
Low-pressure inlet pressure, maximum 10 Bar (145 psig)
Low-pressure outlet pressure, minimum 1 Bar (14.5 psig)
High-pressure outlet pressure, maximum 83 Bar (1200 psig)
Torque, maximum 36 Nm (26.5 lbf-ft)
Maximum speed 1500 rpm
Minimum speed 500 rpm
Filtration requirements (See section 5.8.1) 3 μm melt-blown
Maximum water temperature 50 C (122 F)
Asynchronous motor according to DIN-IEC and VDE 0530 standards.
Voltage and frequency according to IEC 38.
The motors are tted with a rating plate in multi-tension:
380-420 V / 660-720 V, 50 Hz or 440-480 V, 60 Hz
Tolerance ± 5% according to VDE 0530
Insulation according to DIN-IEC 34 Class F
Ambient temperature 40°C, 1000m above
sea level
Class B
Degrees of protection, minimum IP55
Specic application limits are provided in the datasheet of the iSave. Application limits vary
from model to model.
Applications not suitable for the iSave can cause damages to the iSave unit, with risk of
personal injury.

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3.4 Preferred system design
Danfoss recommends building systems with a high degree of safety. The PI&D in chapter
5.16 shows the Danfoss preferred system design.
• It is always the system builders’ responsibility that the system design does not cause any
form of hazard and are adapted to local regulations.
• Proper installation and care of shutdown devices and over-pressure protection equip-
ment is essential.
4.1 Arrival inspection
The iSave is packed in a wood container with plugs in the port connections to protect the
unit from damage during transport.
Remove all packing materials immediately after delivery. Immediately check the shipment
for damage on arrival and make sure that the name plate/type designation is in accordance
with the packing slip and your order.
In case of damage and/or missing parts, a report should be drawn up and presented to the
carrier at once.
The identication label on the iSave states the specic type, the serial number and the code
number of the iSave; see g. below.
The last three digits of the Serial No. indicate the week and year of production.
4.2 Return to the supplier
Flush the iSave with clean water. Drain the iSave and plug the port connections with a cap/cover.
Pack the iSave into a suitable container and make sure that it is suitably fastened to the
container.
Please contact your local authorised distributor or:
Danfoss A/S
DK-6430 Nordborg,
Denmark
Telephone: [phone]
Fax: [phone]
Email: [e-mail]
Homepage: www.ro-solutions.com
4.3 Handling
• Personnel involved in lifting and transportation of the equipment must be trained in
proper handling and safety procedures.
• Observe the local regulations regarding lifting.
• Use suitable, permitted lifting equipment.
• The iSave (set) could slip the lifting arrangement.
• Be aware of individuals located in the operation area while lifting the component.
4. Arrival inspection, handling and storage

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Check the mass (weight) of the iSave unit. All parts weighing more than 20 kg must be lifted
using lifting slings and suitable lifting devices, e.g. an overhead crane or industrial truck.
All iSave units weight more than 20 kg.
Secure lifting slings around the part of the
iSave and the back of the electric motor.
Make sure that the load is balanced before
attempting the lift.
Never lift the iSave unit with only one fas-
tening point.
Incorrect lifting can result in personally
injury and/or damage to the unit.
Never lift the iSave in the bell housing.
Incorrect lifting can result in personally
injury and/or damage to the unit.
4.3.1 Centre of mass

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4.4 Storage
Each iSave is tested before shipment and therefore holds water.
Storage temperature: 1°C to +70°C (33°F to 158°F) – provided that the pump is drained of
uid and stored “plugged”.
Frost protection is required at temperatures below 1°C. Danfoss recommends using DOW-
FROST from DOW Chemical Company or Chillsafe mono propylene glycol from Arco Chemi-
cal Company.
If the iSave is protected against frost, the storage temperature can be: -40°C to +70°C (-40°F
to 158°F)
• The iSave is NOT delivered frost-protected from the factory.
• Only remove caps from the openings of the iSave at the time of installation.
4.5 Outdoor Storage
For outdoor storage cover the iSave (set) with waterproof material.

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5.1 Design details
5 Technical data and design review
5.2 Sound level of the iSave
The noise level from the iSave including the electrical motor is 86 dB (A). Measurements ac-
cording to EN ISO 20361. The test is made under following conditions:
1. iSave and electrical motor mounted on Danfoss base plate.
2. Baseplate is isolated from concrete ground by rubber vibration dampers.
3. Flexible hoses are used on high pressure and low pressure sides of the iSave.
4. Rotation speed 1500 rpm
5. System pressure 60 bar and a booster pressure of 3 bar.
Inuences
Since the iSave is mounted on a base plate and connected to the electromotor by a bell
housing, the noise level can only be determined for the complete unit (system).
It is therefore important that the iSave unit is mounted correctly on a frame with dampers to
minimise vibrations and noise.
It is also strongly recommended to use high-pressure exible hoses between the hard pip-
ing in the RO plant and the iSave. See “hose assembly and installation” in appendix 10.6.
Alternative use multiple exible Victaulic® couplings on the hard piping.
The noise level is inuenced by:
• The speed of the iSave. High speed creates more noise than low speed.
• Rigid mounting of the iSave baseplate generates more noise than exible mounting
• Pipe mounting directly to the iSave increases the noise level compared to exible hoses.
1: 2” Victaulic connections
2: Shaft
3: Low pressure shaft seal
4: Port ange
5: Port plate
6: Valve plate
7: Cylinder drum
8: Port ange
9: Port plate
10: Pins
11: Vanes
12: Port plate
13: Coupling
14: Adapter ange
15: Rotor
16: Stator
17: Port ange
18: Outlet ange

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5.3 Materials
All critical parts of the iSave are made of super-duplex 1.4410/UN S32750 or the like.
Non-critical parts that are not in contact with sea water are made of AISI316.
The shaft to the electrical motor is sealed by a standardised mechanical seal.
For a detailed material/part overview see appendix
5.4 Temperature and corrosion
The chart below illustrates the corrosive resistance of dierent types of stainless steel re-
lated to NaCl concentration and temperature.
Depending on the NaCl concentration, the uid temperature must be between: +2°C to
+50°C (+35.6°F to 122°F).
In order to minimise the risk of crevice corrosion, always ush the iSave according to the
specied start/stop procedure.
5.5 Dimensions and weights
For dimensions and weights please refer to the iSave datasheet. See appendix 10.3.
5.6 Electrical motor data
See datasheet in appendix 10.3 and “Operating and Maintenance instructions, electric mo-
tor” in appendix 10.8.

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5.7 How does the iSave work?
Figure 5.1 shows a section view of the iSave
The iSave consists of a rotating isobaric pressure exchanger and a positive displacement
pump, also called booster pump. The rotation speed of the pressure exchanger and the
pump is exactly the same, as they are driven by the same electric motor.
Fig. 5.1.
5.7.1 Pressure exchanger function:
The pressure exchanger consists of two port plates, one at the concentrate side and one at
the seawater side. In between there is a rotor with several ducts that connect the concen-
trate side with the seawater side.
The pressure exchanger transfers pressure from the high-pressure (HP) concentrate (HP in)
to the low-pressure (LP) seawater coming from low-pressure feed pump (LP in).
To separate the HP side from the LP side there is a sealing zone on both port plates. A single
duct in the rotor is either on the HP side, or on the LP side or in the sealing zone. A single
duct is never in contact with more than one zone at the time. When the rotor rotates a duct
will go from the LP zone over the rst sealing zone into the HP zone, and hereafter from the
HP zone over the second sealing zone and back to the LP zone.
The ow through the HP side of the iSave is forced and controlled by the booster pump.
When the high-pressure concentrate is owing into the iSave it pressurizes the sea water in
the duct coming from “LP in”. The pressurized seawater is then pumped out of “HP out”. Just
before the HP concentrate in the duct comes to the seawater port plate, the duct goes into
the sealing zone and the ow in the duct stops. When the duct goes into the LP zone the
concentrate water is de-pressurized. The (LP) seawater coming from the LP feed pump (LP
in) forces the LP concentrate out of “LP out”.
This pressure exchange process is repeated for each duct with every rotation of the rotor,
and the ducts are thus continuously lling and discharging. The ow on the HP side and LP
side of the iSave is nearly constant over time.
There is no physical barrier in the ducts between the concentrate and seawater. This means
that there will be a small amount of mixing between the two liquids.
When the iSave is rotating the water always ows respectively from LP-in to HP-out, AND
from HP-in to LP-out. However, if the feed ow into LP-in is higher than the ow into HP-in,
some of the LP feed ow will ow directly to LP-out.
When the iSave is not rotating the seawater can only run directly from LP-in to LP-out.
NB!
HP-in
Concentrate
side
LP-out
LP-in
Seawater side
HP-out

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5.7.2 Booster pump
The booster pump is a positive displacement pump, which means that the ow is controlled
by the speed of the electric motor; e.g. if the rotation speed of the electric motor is raised by
10%, the ow will be 10% higher and vice versa. The required rpm can be calculated based
on the “rated ow” of the particular iSave. See datasheet in appendix 10.3.
At low speeds you may hear some minor clicking sounds from the pump. This is normal and
is caused by the pins in the vane pump.
5.7.3 Lubrication flow
To lubricate the moving parts in the pressure exchanger there is a well dened leak be-
tween the port plates and the rotor, as well as in the high pressure bearing between the
pressure exchanger and the booster pump. This leak is typically called “lubricating ow”.
The leaks go from the high pressure side to the low pressure side of the pressure exchanger,
and from the booster pump to the low pressure side of the pressure exchanger.
5.7.4 Mixing
There is no physical barrier in the ducts between the concentrate and seawater. This means
that there will be a small amount of mixing between the two liquids. Because the two liq-
uids are in contact for a short amount of time, the mixing is relatively low.
On the RO market the mixing rate is dened as “balanced ow” when HP-in is equal to LP-in.
Experience from the market shows that the corresponding increase in membrane operating
pressure is about 1 bar.
The customer can reduce mixing by over-ushing the LP feed with excess feed water. See
gure below. Over-ushing means energy loss. Optimal over-ushing is obtained when the
energy loss on LP feed is equal to or less than the energy loss caused by the excess pressure
at the membrane.
5.7.5 How does the iSave work in an RO system?
The gure below illustrates a typical Flow Path of an SWRO or BWRO with an iSave.

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The high-pressure (HP) concentrate (7) ows to the low-pressure (LP) concentrate outlet (3).
The LP sea water (2) ows to the HP sea water outlet (5).
The rotor, moving between the high-pressure and low-pressure streams, removes the high-
pressure concentrate (7) and replaces it with feed water (2).
The ow rate on the HP sea water outlet (5) is controlled by the iSave alone.
The ow rate on the LP concentrate outlet (3) is controlled by the sea water feed pump (1)
and the back pressure valve. This means that changing the LP feed ow (2) will not aect
HP outlet ow (5) and, vice versa, that changing the HP outlet ow (5) will not aect the LP
outlet ow (3).
As LP sea water (2) is ushing the LP concentrate to LP outlet (3), it is essential that the ow
on the LP inlet (2) is equal to or slightly higher than the HP inlet (7). Otherwise there will be
an “under-ush” and higher mixing will occur in the HP outlet (5). This higher mixing will
result in a slightly higher pressure at the membrane.
The booster pump integrated in the iSave must only overcome the pressure drop from the
high-pressure outlet (5) to the high-pressure inlet (7).
During the RO process operation, water is pumped into the HP-membrane feed (6) by the
HP pump (4) and the iSave (5). Almost all water coming from the HP pump (4) penetrates the
membranes (8). Only a slight amount of the water is used as lubrication ow in the iSave.
The lubrication ow is measured as the dierence between the HP pump ow rate (4) and
the permeate ow rate (8). The resistance to permeate in the membrane pressurises the HP
loop.
The isobaric pressure exchanger technology in an SWRO or BWRO change the HP con-
centrate into HP seawater that is feed into the HP membranes. The iSave energy recovery
technology thus signicantly reduces ow needed from the main HP pump (4).
Overall energy consumption of a SWRO or BWRO plant using the iSave depends on the
recovery rate.
The operator can change the recovery rate to optimise the RO system performance. Chang-
ing the recovery rate in an RO system equipped with iSave is easy. Using the VFD, change
the speed of the iSave and thereby the ow in the HP ow rate. Then change the LP feed (2)
ow to the iSave to minimise mixing and optimise energy consumption. Make sure that ow
and pressure are within the rated parameter of the iSave in question.
5.8 Seawater quality
5.8.1 Pre-filtration
It is important that the incoming water is ltered properly to assure optimum service life of
the iSave. A true graded density melt-blown depth lter cartridge rated at 3 μm is therefore
recommended. Poor pre-ltration of the feed water will result in reduced service life of the
iSave.
The iSave may request a dierent pre-lter of the seawater than the HP pump and other
components in the RO system.
As the various lters on the market dier greatly, Danfoss RO Solutions recommends us-
ing cartridges with consistent, reliable performance and high eciency, in which bres
are blown continuously onto a central support core.
Danfoss RO Solutions does not recommend cartridges requiring any type of binders or
resins.
NB! Filters can be purchased from Danfoss RO Solutions.
NB!

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For more information on the importance of proper ltration, please consult our publication
“Filtration”, which also will provide you with an explanation of ltration denitions and guid-
ance on how to select the right lter. See section 5.8.1 for lter installation instructions.
5.8.2 Air bubbles
Large bubbles in a pressurised RO system can result in damage to piping and equipment. All
air must be bleed from both the LP and HP before the RO system is pressurised.
Special consideration should also be given to air bubbles in feed ow, continuously fed into
the HP pump and iSave.
5.8.3 Chemicals
The iSave should not be exposed to chemicals that will damage the RO membranes.
5.9 Initial start up and ushing
Prior to the initial start-up, all piping associated with the iSave unit should be thoroughly
ushed to assure that no impurities enter the iSave. Inadequate pre-ushing will strongly
aect the life of the iSave and may lead to its eventual breakdown.
It is recommended to disconnect all connections to the iSave and to thoroughly ush the
piping before the iSave is connected to the inlet and outlet connections.
It is essential that the water used for the nal pre-ush is pre-ltered to a level described
in chapter 5.8
It is recommended to install temporary basket strainers at both inlets to the iSave during
the initial start-up and commissioning.
Also see “Instruction for start and stop of the SWRO with iSave unit” in appendix 10.1.
5.10 Initial start-up and settings of safety equipment
The high-pressure pump feed water into the high pressure line may be able to generate a
pressure higher than the maximum allowable pressure in the system. There is thus a risk of
personal injury and/or damage to the iSave.
Depending of the type and size of the feed pump of the RO system, this pump may be able
to generate a pressure higher than the maximum allowable pressure in the LP system. There
is thus a risk that the iSave or the LP equipment could be damaged by over-pressurisation.
To prevent such over-pressurisation, appropriate relief valves should be used and proce-
dures should be implemented to safeguard the HP and LP sides of the iSave and/or the RO
system.

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5.11 Flushing
RO membranes require periodic ushing to limit biological fouling.
There are two types of ushing: feed water (Seawater) ush and fresh water (Permeate)
ush.
Regardless of the ush water used, the water must be pre-ltered to the level described in
chapter 5.8. All parts of the iSave must be ushed, i.e. LP- and HP ow channels.
Feed water ushing is part of a normal shutdown sequence. After the HP pump has been
stopped, the permeate and concentrate production will continue until the high-pressure
drops below the osmotic pressure. Both the iSave and the LP seawater feed pump must run
until the conductivity measured at point (7) and (3) are satisfactory. See also P&ID in chapter
5.16.
Fresh water ushing is performed before every extended shutdown of the RO plant.
Permeate is simultaneously fed into the iSave at LP in (2), and either to the HP pump inlet
(1) or through some other injection point such as the CIP connections or full ow cleaning
connection. See also P&ID in chapter 5.16. Permeate may be produced during this ushing
process.
Special attention should be given to the pressure in the HP line (7) as the iSave may start to
cavitate when it runs at high speed and the pressure in the HP line (7) drops below 3 bars.
This can be avoided by reducing the speed of the iSave to about 750 rpm and keeping the
pressure in the HP line at the minimum of 1 bar. At this low pressure the iSave may only run
for a maximum of 10 minutes.
Failing to ush the iSave with fresh water before extended shutdowns may result in ex-
tensive biological growth and cause corrosion in the iSave and other equipment in the RO
system.
5.12 CIP or membrane cleaning
The purpose of membrane cleaning is to reduce scaling and fouling in the membranes. For
optimal performance specic chemicals are required, depending on the cause of the pollu-
tion. After chemical treatment the system must be ushed with fresh water.
The ush water coming out of the membranes may consist of a large amount of suspend-
ed inorganic particles. It is important to assure that these particles are not lead into the
iSave.
It is essential that the water used for the nal pre-ush is pre-ltered to a level described
in chapter 5.8.
The iSave should not be exposed to chemicals that will damage the RO membranes
Also see instruction “Membrane cleaning of RO system with iSave unit” in appendix 10.2.
5.13 High pressure remains after shutdown
The HP line of the RO system equipped with an iSave can remain pressurised for a long time
after shutdown. Pressure decreases as water slowly leaks through the iSave. If more rapid
system depressurisation is required, the system should be bled through a suitable valve on
the HP concentrate line.
Always check the pressure in the high-pressure lines before making service in the HP lines
or pressurised equipment.
NB!

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5.14 Over-pressurisation caused by low pressure isolation
If the low-pressure side of the iSave is blocked and the iSave is exposed to high-pressure,
there is a risk that the iSave or the LP piping could be damaged by over-pressurisation.
To prevent such over-pressurisation, appropriate relief valves should be used and proce-
dures should be implemented to assure that the HP of the iSave is depressurised prior to
the isolation of the LP side.
5.15 Over-pressurisation caused by the high pressure pump.
The HP pump may be able to generate a pressure higher than the maximum allowable
pressure for the iSave or the system – particularly if the HP pump is a positive displacement
pump, the pump will be able to generate extremely high levels of pressure.
To prevent such over-pressurisation, appropriate relief valves should be used and pro-
cedures should be implemented to assure that the HP of the iSave is protected against
excess pressure.