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    Freshwater Generators from Wärtsilä

    Also known as 'Serck Como'

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Multi Stage Flash Evaporators

MSF flash evaporator, marine desalination plant with lowest lifecycle cost in the market. Up to 1500 tons/day

Wärtsilä's Multi-Stage Flash (MSF) evaporator is used for producing distillate (fresh water) from sea, well or industrial water. A specific advantage of the multi-stage flash technology is that the heat consumption - or thermal efficiency - can continuously be adjusted to the set requirements of each application. The MSF is able to produce up to 1500 tons of distillate per day.

The Multi Stage Flash is one of the most reliable thermal seawater desalination plants in the world. It is the only evaporator technology that strictly separates heat transfer and evaporation, minimizing the risk of scaling and greatly reducing maintenance costs.

The distillate produced by a MSF has a very low salt content (conductivity < 4 μS/cm). This makes it very suitable to be used as technical water (e.g. boiler feed water). The distillate quality and quantity are not impacted by the seawater temperature. The MSF is therefore a reliable source for freshwater on board of ships and offshore platforms. It can also be used for many land-based applications.


    • Either steam, engine jacket water or combination can be used for heating.
    • Full-automatic or semi-automatic operation.
    • Can be operated in part load.
    • Heat transfer and evaporation are taking place in different areas, resulting in a minimised risk of scaling.
    • Sturdy construction with low maintenance demands resulting in high availability.
    • Solution with lowest sensitivity to malfunction & lowest lifecycle costs.
    • Components in contact with seawater or distillate are manufactured with corrosion resistant materials, e.g. copper-nickel.
    • Flexible dimensions allow for best utilisation of space.
    • Operating frequency converter for pumps saves energy.
    • Water conductivity < 4 μS/cm


    • Capacity up to 1500 t/d. 
    • Steady production of freshwater at seawater temperatures 0 - 32°C. 
    • Either steam, engine jacket water or combination can be used for heating 
    • Full-automatic or semi-automatic operation
    • Can be operated in part load

    Materials used:

    • Condenser tube material: CuNi, CuZn  
    • Pipes in contact with seawater: CuNi 
    • Pipes in contact with steam, motor-water, condensate: Steel 
    • Distillate: CuNi  
    • Shell: CuNi 


    After leaving the first stage condenser (3), the seawater flows through the brine heater (1), where the heat input to the plant (steam or engine jacket water) causes a further temperature increase.

    The seawater leaves the brine heater (1) and enters the first flash chamber (2), reaching a brine top temperature of approx. 80°C.

    At this point the pressure of the incoming seawater is suddenly reduced, by means of an orifice, below its equilibrium vapour pressure resulting in explosive boiling or evaporation (flashing). The pure vapour produced is then condensed, giving up its latent heat to preheat the incoming seawater (3).

    If this process is repeated over a large number of effects, at successively lower pressures and temperatures, large distillate production rates at reasonable performance ratios can be achieved.

    Process flow within a Wärtsilä Water & Waste (Serck Como) Multi Stage Evaporator; MSF process illustration


    System Capacity (ton/day) Power (kW) Dry weight (kg) Wet weight (kg) Footprint
    (L x W x H, mm)
    MSF 115-5 115 915 18000 21000 5700 x 2900 x 3000
    MSF 300-6 300 2388 27000 32000 7300 x 2900 x 3300
    MSF 650-6 650 5146 37000 45000 9200 x 3500 x 3900
    MSF 775-8 775 4812 42000 52000 10500 x 3600 x 3900
    MSF 850-8 850 4780 43000 53000 11700 x 4200 x 3900
    MSF 950-8 950 6395 45000 55000 12000 x 3700 x 3900

    Capacity up to 1500 ton/day.
    Steady production of freshwater at seawater temperatures 0 - 32ºC.
    Water conductivity of distillate for all models: < 4 μS/cm.


    Delivered as standard:

    • Flash vessel with condenser and condenser tubes
    • Base frame
    • Pumps, including e-motors
    • Air ejectors
    • Feed water heater
    • Distillate cooler
    • Complete internal pipework
    • Control equipment and instrumentation
    • Optional steam booster


    • Steam booster
    • Distillate cooler
    • Frequency converters for pumps
    • Cleaning stations

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