Danfoss iSave 40, Руководство по эксплуатации

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Operation guide | iSave 40
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180R9239 | AQ299555093252en-001601 | iSave 40 | 09.2022
Also see instruction “Membrane cleaning of RO
system with iSave unit” in appendix 10.3.
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.
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.
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.
5.12 CIP or membrane cleaning
The purpose of membrane cleaning is to reduce
scaling and fouling in the membranes. For
optimal performance specific chemicals are
required, depending on the cause of the
pollution. After chemical treatment the system
must be flushed with fresh water.
The flush water coming out of the
membranes may consist of a large
amount of suspended 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
final pre-flush is pre-filtered to a level
described in chapter 5.8.
The iSave should not be exposed to
chemicals that will damage the RO
membranes.
Always check the pressure in the
high-pressure lines before doing service
on the HP lines or pressurised equipment.
To prevent such over-pressurisation,
appropriate relief valves should be used
and procedures should be implemented
to assure that the HP of the iSave is
protected against excess pressure.
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 3 bar. At
this low pressure the iSave may only run
for a maximum of 10 minutes.
Failing to flush the iSave with fresh water
before extended shutdowns may result in
extensive biological growth and cause
corrosion in the iSave and other equip-
ment in the RO system.
To prevent such over-pressurisation,
appropriate relief valves should be used
and procedures should be implemented
to assure that the HP of the iSave is
depressurised prior to the isolation of the
LP side.
5.11 Flushing
RO membranes require periodic flushing to limit
biological fouling.
There are two types of flushing: feed water
(seawater) flush and freshwater (permeate) flush.
Regardless of the flush water used, the water
must be pre-filtered to the level described in
chapter 5.8. All parts of the iSave must be
flushed, i.e. LP- and HP flow channels.
Feed water flushing 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 conduc-
tivity measured at point (7) and (3) are satisfac-
tory. See also P&ID in chapter 5.16.
Fresh water flushing 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 flow cleaning connection. See also P&ID in
chapter 5.16. Permeate may be produced during
this flushing process.
To prevent such over-pressurisation,
appropriate relief valves should be used
and procedures should be implemented
to safeguard the HP and LP sides of the
iSave and/or the RO system.