RayCleanTM Ballast Water Treatment System


The RayCleanTM ballast water treatment system is type approved by IMO and DNV-GL and can treat ballast water at any flowrate from 30 – 3000 m3/h. The system is based purely on mechanical treatment and therefore it does not involve any use of chemicals or active substances. First treatment step is filtration, second step is UV treatment.

The system can be delivered in special EX-version suited for installation in hazardous areas.




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RayCleanTM has no salinity or temperature limitations and has been proven effective in water with UV-T (UV-Transmission) as low as 0.33, which sets the industry benchmark! Learn more about UV-Transmission by watching our UV-T movie or download our UV-T leaflet.

The UV treatment takes place in units with a flow capacity of 300 m3/h. Each UV unit is equipped with 60 highly efficient low-pressure UV lamps. These lamps are roughly twice as energy efficient as the widely used medium pressure UV lamps, and as they work at much lower temperature they have superior lifetime and no issues with regard to fouling.

Constant online monitoring of the UV intensity inside each unit is used to dim the UV lamps in very clear water (high UV-Transmission) in order to save energy, and to reduce the flow through the unit in extremely unclear water (low UV-Transmission). This ensures a carefully dosed UV treatment at all times resulting in IMO and USCG compliance even in extremely challenging water conditions. All lamp dimming and flow control is fully automatic.




Features Remarks
1. Treatment consisting of mechanical filtration and UV treatment. Well proven treatment combination that has been used for decades in many different water treatment applications.
2. Full treatment during both ballast water uptake and ballast water discharge. Full treatment also during de-ballast ensures full IMO and USCG discharge compliance even in cases with re-growth of organisms in the ballast tanks.
3. Operation of system is fully automatic and only requires “start operation” and “stop operation” input from the crew. This input is given by simply pushing a button on the control touch screen. Use of the RayCleanTM BWTS does not impact the daily routines and procedures onboard the vessel.
4. System is equipped with 15” touch screen which clearly displays the main components of the system, the actual operation parameters (flow rate, UV intensity, differential pressure over filter, valve positions) and any alarms or errors. This ensures easy operation and clear indication of the exact location or UV-lamp in case of problems.
5. System is tested and approved for treatment of ballast water with all salinities. From fresh water, to brackish water, to marine water. The system is one of the very few approved for operation in all typical water conditions around the world.
6. System is tested and approved for treatment of ballast water with very low UV-T, as low as 33% The system is one of the very few approved for operation in all typical water conditions around the world.
7. System is approved for operation in all normal water temperatures, from sub-zero (as long as the water stays liquid) to 40+ deg. C. The system is one of the very few approved for operation in all typical water conditions around the world.
8. Mechanical filter includes automatic backflushing. Cleaning is automatic and does not require any action by crew.
9. UV treatment based on highly efficient low pressure UV lamps The RayCleanTM UV lamps play an important role in the low power consumption and excellent treatment performance demonstrated by the system. In addition, the low pressure lamps eliminate one of the concerns with medium pressure UV lamps: they contain liquid mercury, which is dangerous if a UV-lamp breaks. The low pressure lamps used in the RayClean system contain amalgam which is a solid that is not dangerous and easy to clean if a UV lamp breaks.
10. UV lamps have a lifetime of approx. 12000 hrs. Replacement of UV lamps only takes place one to three times during the lifetime of a typical ship.
11. UV unit includes dimming functionality to reduce power consumption when the treated water is clear. Ensures lowest possible power consumption at all times.
12. UV unit includes automatic cleaning of UV quartz tubes after and before each ballast operation. The cleaning is done by sliding Teflon scraper rings along the quartz tubes. The cleaning operation is fully automatic and without involvement from crew. Removes problems with fouling or staining of quartz tubes due to deposits on the tubes between ballast operations.
13. Very short start-up time, less than 2 minutes.

This ensures minimum interference with the normal ballast operations onboard the vessel.



RayCleanTM Technical Data

Capacity [m3/h] System Power
Consumption* Max. [kW]
System Power
Consumption* Min. [kW]
Weight [kg] Foot Print** [m2]
100 21 11 1425 5
200 21 11 1425 5
300 21 11 1675 5
400 42 22 2525 6
500 42 22 2975 6
600 42 22 2975 6
700 63 33 3825 8,5
800 63 33 4075 8,5
900 63 33 4075 8,5
1000 84 44 4925 10,5
1100 84 44 4925 10,5
1200 84 44 5375 10,5
1300 105 55 6175 11,5
1400 105 55 6175 11,5
1500 105 55 6175 11,5
1600 126 66 7525 12,5
1700 126 66 7525 12,5
1800 126 66 7525 12,5
1900 147 77 8325 14,5
2000 147 77 8875 14,5
2100 147 77 8325 14,5
2200 168 88 9725 16
2300 168 88 9725 16
2400 168 88 9725 16
2500 189 99 11075 17,5
2600 189 99 11075 17,5
2700 189 99 11075 17,5
2800 210 110 11975 19
2900 210 110 11975 19
3000 210 110 11975 19

* Power consumption excludes optional filter backflush pump
** Footprint including electrical panels

Treatment System Pressure/Pressure Loss
Required inlet pressure of the treatment system:    Minimum 2 bar / maximum 9 bar
Total pressure loss of the treatment system:           0.5 bar

Utility requirement:
3 x 230V, 50/60Hz – 10A for main control panel and 3 x 63A per UV control panel

Why Low Pressure UV-lamps?

As one of the very few ballast water treatment systems on the market, the RayCleanTM system utilizes highly efficient low-pressure UV lamps, as opposed to the more commonly used medium pressure UV lamps. The low pressure UV lamps have a number of distinct advantages which makes them the optimum choice for ballast water treatment:

  RayCleanTM low pressure UV lamp Medium pressure UV lamp

Converts approx. 35% of input power to useful UVC light.

Only half the electrical power is required to generate the same UV treatment

Converts approx. 18% of input power to useful UVC light.
Lamp lifetime 12,000 hrs. 3,000 – 4,000 hrs.
Operating temperature

150 deg. C.

The low operating temperature eliminates problems with dirt and mineral deposits that are common on medium pressure lamps. In addition, it is not a problem if the UV lamps are not fully submerged in water at all times. This is a requirement for medium pressure lamps.

800 – 1,000 deg. C.
Start-up time

Less than 2 mins.

The short start-up time means there is minimum interference with the normal ballast operations on a vessel.

8 – 10 mins.
Mercury content

Extremely small amount contained in amalgam in solid form.

It is safe and not a problem to break a UV lamp. Broken glass and amalgam can simply be collected and removed without any special precautions or equipment.

Larger amount contained in liquid form.

If a medium pressure lamp is broken, the area should be evacuated and specially trained and equipped personnel should clean the area.


RayCleanTM Safety

In the design and development of the RayCleanTM system safety has been a top priority. This means safety for the crew, the vessel and the environment:

  • Crew safety: The system is purely mechanical which means no chemicals must be handled by the crew, not even for cleaning. Safety features ensure automatic system shutdown in case of no water flow, overheating or too high pressure. If a UV lamp breaks during replacement there is no liquid mercury inside the UV lamp and therefore no health risk for the crew.
  • Ship safety: The system generates no by-products or explosive substances during operation. The chemical composition of the water is not altered during treatment, which means there is no risk of increased corrosion.
  • Environmental safety: No chemicals and/or neutralizing chemicals are used and therefore there is no risk of discharging chemicals and its by-products to the environment. The power consumption of the RayCleanTM system is the lowest in class which helps to keep engine emissions (CO2, NOX, SOX) at a minimum.


RayCleanTM Automation

RayCleanTM is fully automated and based on a PLC platform, which controls the valves, pumps, UV sensor, flow meters, pressure- and temperature sensors. RayCleanTM consists of two types of control panels: a Master Control Panel and a number of UV Control Panels, one for each UV unit.

RayCleanTM is controlled by the PLC located in the Master Control Panel. The UV Control Panels are connected to the Master Control Panel via a Profinet Ring bus. The Master Control Panel has a 15” colour graphic touch screen (also called HMI). This is used for local control of the system, but as an option one or more remote HMI’s can be offered and integrated into the solution. Alternatively the RayCleanTM automation can be integrated into the existing vessel automation system.

The operation of the system is made as simple as possible. The operator only has to start and stop the ballast and de-ballast operation and the remaining part of the operation is then fully automatic. RayCleanTM is automatically optimizing the power consumption via dimming of the UV lamps and regulation of the flow in accordance with the characteristics of the water. During ballast and de-ballast operations the control system is logging the operation data and time-stamp the date before it is saved into a log file.


What is UV-Transmission?
UV-T is a measure of the capability of UV light to penetrate into the water. When the UV-T is high, close to 100%, the water is very clear and the UV light can penetrate deep into the water. On the other hand, when the UV-T is low (below 50%) the water is very un-clear and the UV light can only penetrate a limited distance into the water.
In the figure below two cases with different UV-T are illustrated; one case with high UV-T of 90%, and one case with just 50% UV-T.





In the graphs it is illustrated how rapidly the UV intensity decays away from the UV-lamp.
With a UV-T of 90% the UV intensity is 81% 2 cm away from the UV lamp, whereas it has dropped to a UV intensity of just 25% 2 cm away from the lamp when the UV-T level is 50%.

UV-Transmission of ballast water
The UV-T found in different ports around the world varies significantly. Some ports are located at river estuaries which means the water in the port is fresh water containing high amounts of sediments, organic particles and dissolved organic compounds. This makes the UV-T very low. Other ports are located on islands in the middle of an ocean, and here the UV-T is typically high.

Port UV-T
Skagen, Denmark 92%
Tanjung Pelepas, Malaysia 83%
Brisbane, Australia 92%
Melbourne, Australia 87%
Lisboni*, Portugal 41%
Zeebrugge, Belgium 85%
Bremerhaven, Germany 60%
Porto Grande, Cape Verde 92%
Brunswick, GA, USA 51%
Wallhamn, Sweden 91%
Shanghai, China 49%
Vera Cruz, Mexico 94%
Houston, USA 74%
New Orleans, USA 54%
Shanghai, China 55%
Hong Kong, China 80%
Antwerp, Belgium 66%
Rotterdam, Netherlands 93%
Lisbon, Portugal 53%
Yangzte river, Taizhou 37%

*Minimum observed level which lasted just a few minutes 


UV-Transmission limit of DESMI Ballast Water Treatment Systems
Only a few systems can cope with UV-T level below 50%. The DESMI systems can and sets the industry benchmark regarding UV-T limitation. The RayCleanTM system holds the absolute record with a UV-T limit at just 33%.


This remarkable performance is a result of the UV unit design and the unique capability of reducing the flow in extreme cases. The RayCleanTM system constantly monitors the UV intensity inside the UV unit, and if it is lower than a certain threshold, the flow through the unit is automatically reduced. This ensures compliance with IMO and US Coast Guard discharge standards at all times, and even in extreme cases where no other system on the market can treat the water. In reality this flow reduction is only rarely utilized. The table show how the flow through one 300 m3/h RayCleanTM UV unit is reduced at different UV-T levels.

Port UV-T RayClean flow, per UV unit
Skagen, Denmark 92% 300
Tanjung Pelepas, Malaysia 83% 300
Brisbane, Australia 92% 300
Melbourne, Australia 87% 300
Lisboni, Portugal 41% 200
Zeebrugge, Belgium 85% 300
Bremerhaven, Germany 60% 300
Porto Grande, Cape Verde 92% 300
Brunswick, GA, USA 51% 270
Wallhamn, Sweden 91% 300
Shanghai, China 49% 250
Vera Cruz, Mexico 94% 300
Houston, USA 74% 300
New Orleans, USA 54% 300
Shanghai, China 55% 300
Hong Kong, China 80% 300
Antwerp, Belgium 66% 300
Rotterdam, Netherlands 93% 300
Lisbon, Portugal 53% 295
Yangzte river, Taizhou 37% 140
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