Diesel Engine Cooling System – Water Purifiers Instead of Chemicals for Color Line

By George Backwell at January 17, 2011 02:58
Filed Under: General

Early on in the evolution of the marine diesel engine it became evident that even good quality jacket cooling water contained microscopic particles that would build up to insulate the cooling surfaces. Scale was found to seriously diminish both engine efficiency and engine life, thus engine manufacturers looked to the laboratory for answers as to how this unwelcome reaction between very hot water and metal might be prevented.

The chemists suggested additives to the cooling system. The kind of mix that engine manufacturers demand be be added to a decent fresh-water supply nowadays mostly has a nitrite-borate base‚ with a complex blend of organic inhibitors, surfactants, alkali adjusters, dispersants and foam suppressers. Problem solved; or was it?

Corrosion in the Cooling System and Disposal of Waste Water

Long term research by engine makers has revealed that despite, or even because of, the cocktail of chemicals added to the diesel cooling system, localised pitting occurs in the jacket cooling water channels, and such pitting provides fertile sites for metal corrosion.

The second difficulty has more immediate financial implications for the shipowner: whenever an engine cooling system is drained within a MARPOL recognised 'Special Area'/Emission Control Area (ECA) the waste water should be kept on board in designated tanks (lessening revenue-earning deadweight capacity) until discharged to a port reception facility.

Alternative System of Water Treatment for Diesel Engine Cooling System

Looking for answers, Color Line, of Norway, decided to try out an alternative (in co-operation with main diesel engine manufacturer Wärtsilä –  a water purifier plant treatment of the diesel engine cooling system  – without the use of chemical additives. They chose their huge Color Fantasy ferry for the extended trial (75,027 gt, with a capacity of 2,750 passengers). This cruise ferry with sister ship Color Magic plies the sea route between Oslo and Kiev in the Baltic Sea, one of the world's largest brackish water areas with a unique ecology to be protected by the legitimacy of its 'Special Area' status.

Cruise Ferry 'Color Fantasy': Courtesy of Color Line

According to the ENWA Water Treatment Company's online news item on 13, January 2011, tests of its chemical-free water treatment system (trademarked, 'EnwaMatic') aboard the Color Fantasy ran over a period of several years spanning no less than 16,378 engine hours of operation of its four 8-cylinder Wärtsilä mediuim-speed L46 main engines (attached in pairs via flexible couplings, to twin input/single output Renk reduction gearboxes turning twin Rolls Royce controllable pitch propellers).

Evidently the tests proved successful, for engine manufacturer Wärtsilä has now formally approved the 'EnwaMatic' for use with its marine diesel engines, and at the same time Color Line announced that it would be installing the same system in all nine ships of a fleet that links Norway with five other countries bordering the Baltic Sea. An eco-friendly decision that also seems to make economic sense.

'EnwaMatic' Water Treatment Unit: Photo courtesy of ENWA Water Treatment

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