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1
System Summary
Production Capability: Model T8- 0.33 m3/Hour (8 m
3/Day)
Model T12- 0.5 m3/Hour (12 m
3/Day)
Model T16- 0.66 m3/Hour (16 m
3/Day)
Electrical Load: 6.25 kW
Standard Voltage: 440V/3-Phase, 50 Hz/60 Hz
Alternative Voltages Available
Noise Level: 85 Db
System Design Parameters
Feed Water Flow: 2-2.3 m3/Hour
Feed water Pressure: 35 PSI (2.4 BAR)
Feed Water P.H. level: 2-11
Feed Water SDI: 5
Feed Water Salinity: 35,000ppm NaCl
Nominal Feed Water Temperature: 25oC
Feed Water Temperature Range: 5-350c
Salt Rejection: 99.4%
Working Pressure: 850PSI (58 BAR)
Product Flow/Membrane Rating: +/-15%
Product Water Quality: <450ppm
Weights (Including Primer Pump): Model T8- 190 kg
Model T12-220 kg
Model T16-250 kg
2
Principles of Reverse Osmosis
Reverse Osmosis (RO) is a low cost method of desalination, and is excellent for both marine and land
based applications.
Osmosis is a naturally occurring process and is defined that when two solutions of different
concentrations are separated by a semi-permeable membrane then the less concentrated (purer) water
will flow towards the saltier (more concentrated) side of the membrane. This will happen until the
pressures and concentrations are equalised.
The Cathelco Seafresh desalination plant reverses this process by pressurising salt water at double the
natural osmosis pressure against the membrane surface, resulting in potable water being produced.
The principal of operation is such that the feed water has passed through a strainer (or similar) to
ensure feed water is free of large debris before entering the system. Sea water is pumped by a priming
pump through a series of pre-filters to extract any free particles to a designed micron size according to
the operating conditions.
The filtered feed water then passes through the high pressure pump which increases the pressure to
800 – 900 PSI (55-62 BAR) prior to entering the membrane(s).
Each membrane is held in the centre of a high pressure casing. The pressurised feed water is fed
through the membranes and discharged through a pressure regulating valve to sea water discharge.
The product water which permeates through the membranes is piped through a salinity sensor to a
solenoid valve which diverts the fresh water either to store or to dump depending on the quality. This
operation is controlled by a temperature compensated controller set to reject water that is not well
within the WHO directive of a maximum 500ppm salinity for potable water.
Although the product water is suitable for potable storage directly from the Cathelco Seafresh plant, it
can be treated in various ways including ultra violet sterilisation, active carbon filtration, re-
mineralisation and chlorination. These are available as optional extras and are detailed later in the
document.
Product water without chlorine treatment tastes better but for long term storage chlorine dosing is
advisable.
Every unit is manufactured to Cathelco Seafresh exacting standards, and is comprehensively tested prior
to despatch to ensure safety and operational excellence.
3
Component Description
The standard system consists of the following components which are housed within one main control
frame. The frames are Aluminium, epoxy powder coated in white. Suitable shock mounts are supplied
with the plant. Only the Primer pump is supplied outside the frame to be installed on or below the
waterline. Other optional items such as Media Filter, Re-Mineralisation and Fresh Water Flush are
supplied separately.
1. PRIMER PUMP
This pump is installed on or below the waterline and forces water through the pre-filter units
and delivers it to the high pressure pump with a positive pressure. The pump also features a
maintenance inlet, used to introduce chemicals into the system.
Type: Single stage centrifugal
Materials: Bronze pump body, Bronze Impeller, 316 SS Shaft
Speed: 2900 RPM
Power: 0.75 kW, 2.3 A
2. PRE-FILTERS
This consists of two disposable cartridge filters mounted in series fitted with bleed buttons for
simple removal of air from the system. A 25 micron filter element followed by 5 micron element
ensures “clean” water passes into the high pressure pump and membranes. Clear filter
housings make it easy to see when the elements are in need of cleaning/replacing, this will be
dependent on the quality of the feed water. Polyester elements are used instead of cotton as
they are a poor host for bacteria and fouling. For systems fitted with a media filter, only a 5
micron element is required.
Size: 4.25” x 20”
3. HIGH PRESSURE (HP) PUMP
The high pressure pump delivers the pre-treated seawater to the membranes and pressurizes it
to working pressure (850 PSI / 58 BAR). The pump is fitted with a vibration dampener for
smoothing of outlet flow water. The pump is belt driven from a four pole T.E.F.C motor. The
assembly includes a mechanism for tightening a loosening of the drive belts.
Type: Triplex plunger
Materials: Nickel Aluminium Bronze pump body, die cast Aluminium crankcase, 316 SS valves
and seats
Speed: 1040 RPM
Power: 5.5 kW, 440v 3ph- 11 A
4
4. PRESSURE VESSELS AND MEMBRANES
The R.O. membranes are housed in GRP pressure vessels sealed with stainless steel reinforced
nylon end plugs. Depending on the model the system will have two, three or four membranes in
series. Interconnecting pipe work is made from super duplex stainless steel joined with Victaulic
couplings.
Membrane type: Dow Filmtec SW30 4040
Sodium Chloride Rejection: 99.4%
Max operating pressure: 1000 PSI (69 BAR)
Vessel Test Pressure: 1500 PSI (103 BAR)
5. CONTROL PANEL / SYSTEM CONTROLS
The system features simple electronic controls for ease of operation. These controls are housed
in an IP55 rated, powder coated steel enclosure. The features include:
• Membrane keypad for operation of system
• Fully automated Salinity Controller showing quality of product water in TDS
• Audible alarm with mute button in addition to LED’s to indicate fault states
• High pressure switch set to shut down system if the pressure exceeds 1000 PSI (69 BAR)
• Low pressure switch to protect HP Pump from cavitations in feed water create by low feed
pressure
• Hour meter
• Fresh water flush switch (optional)
6. WET CONTROLS
• Feed pressure gauge(s) to indicate clogging of pre-filters and media filter
• Restrict valve and high pressure gauge to regulate working pressure
• Inlet flow meter
• Product flow meter
• Product water sample tap
7. CONNECTIONS
Sea inlet: 1” BSP
Brine discharge: 1” BSP
Fresh water: 1/2” BSP
Both sea dump and fresh water lines are fitted with over pressure relief valves. The system also
features a 1” maintenance inlet connection mounted on the Primer pump, and a 1”
maintenance outlet connection within the main frame.
10
Optional Extras
Media Filter
Commonly referred to as a sand filter because the filter media is borosilicate grit which looks like beach
sand. This is an FRP housing containing specially calibrated filter media. Particles present in the feed
water get caught in the upper layers of the media. The flow through the housing can be reversed to
flush the “dirt” out through the discharge pipe. This unit significantly lowers the consumption of the
cartridge filter elements when the plant is operated in dirty water. For systems using a media filter, only
a 5 Micron pre-filter is supplied.
Oil/Water Separator Element
A pre-treatment option for use with feed water that may contain oil. The unit uses the same type
housing as the standard pre-filters for compatibility and ease of replacement.
UV Sterilizer
The unit sterilises the water to be completely free from bacteria, parasites and algae spores. This can be
used for pre-treatment of feed water when operating in dirty waters and also as a post treatment if the
water has been held in storage for long periods of time.
Fresh Water Flush
Upon system shut down the fresh water flush system allows the user to flush potable water through the
system. This ensures maximum operational efficiency and longevity of the R.O membranes.
The system is plumbed into the vessels pressurized fresh water system and features a carbon filter to
remove any chlorine that may be present.
Re-Mineralization
Used to restore mineral content and restore equilibrium with alkalinity/CO2 levels. Also known as re-
hardening or de-acidification. The unit uses the same type housing as the standard pre-filters for
compatibility and ease of replacement.
Carbon Filter
Removes dissolved gases (including Chlorine), tastes and odours to improve the taste of the product
water. This unit uses the same housing as the pre-filtration cartridges for compatibility and ease of
replacement.
Remote Keypad
This keypad allows the user to control both pumps and assess the running status remotely to the plant.
Chlorine Dosing
The unit sterilises the product water to be completely free from bacteria, parasites and algae spores.
Chlorine is added to the product water (0.2-0.3mg/l in accordance with W.H.O rules on potable water)
to sterilise it for storage for long periods of time.