Sea water – evaporator on a ship

User: THENAMARIS INC, Shipping company in Greece

We are still proud of our first application in the marine industry, as early as 2001. We were immediately quite successful in solving problems related to seawater desalination. Since then, we have been able to install Merus rings on hundreds of other evaporators to achieve the same results, independed on the type of evaporator.

On seawater evaporatorthe majority of the cargo vessels or ships, there is one or more evaporator, to ensure the water supply when on sea. This desalination is used to make out of seawater, drinking water. In order to achieve drinking water quality, the solved salts and other inpurities has to be removed from the seawater.
Engineers found an economical solution to perform this process to evaporate the salt water, by using the excess energy of the motors. In addition, the desalination process works under lower pressure. This negative pressure reduces the boiling point of the water, so that the temperature does not have to be 100°C. Depending on the vacuum in the boiler, the sea water can evaporate at 80°C. The steam produced is condensed and the water is later used as drinking water or for technical purposes requiring salt-free water. The rest of the water, known as brine, is returned to the sea.
RO systems can now be seen as water treatment on certain ships. Reverse osmosis requires electrical energy to work instead of excess heat from the motors.
Togehter with the seawater or brakish water, salt and other substances from the sea enter the desalination system. If the water isnt treated over time the inner surface in the evaporators gete coated with a crust of deposits. This builds up over time and hinders heat transfer and herewith the evaporation. As a result, the output decreases from day to day, until the required amount of fresh water can no longer be produced.

A traditional solution to this problem is chemical and / or manual cleaning of the system. Manual means disassembly, cleaning plate by plate and reassembling with new gaskets. Both methods are very expensive and time-consuming. No water is produced during cleaning.

Improve the performance of an evaporator using Merus Ring

We installed two Merus Rings at each sea water inlet. Furthermore there were two Merus Rings at a chemically cleaned boiler (A) and two more at a second boiler (B) which hadn’t been cleaned for a long time. In both cases one Merus Ring would probably have been sufficient, to ensure the results we decided to play safe with two Merus Rings.

The result

In the first boiler (A) no cleaning was needed anymore, after the installation of the Merus Rings. Astonishingly the performance in the first month of the installation did not only remain stable, but even increased from 28 to 31 t of fresh water in one day. The explanation for this is that chemical cleaning is not able to reach all areas of a piping system. Whereas the Merus technology can act wherever water is.

The second boiler (B) similar to (A) didn’t need further cleaning. The production volume increased very fast and reached its maximum performance soon. This means that this boiler is now fully clean and no further cleaning is necessary anymore.

Abandoning chemical cleaning is also a great benefit for the life time of the system as this can lead to heavy corrosion.


We use cookies to ensure that we give you the best experience on our website and to improve the relevance of our communications with you. If you continue without changing your settings, we’ll assume that you are happy to receive all cookies on the merusonline website. However, if you would like to, you can change your cookie settings or find detailed information about how cookies are used on this website by going to 'Data protection'.