WHY there is NEED FOR ADDITIVE in jacket cooling water in ENGINE system .THE reasons are:
=Fresh water is used for cooling medium cylinder cover, liner, exhaust valve,turbocharger. 1.However acid and oxygen dissolved in water can corrode the surface 2.salt in water can form scales and impair heat transfer .
=Hence fresh water is used no salt only dissolved oxygen. A corrosion inhibitor additive is added to prevent corrosion. Most corrosion inhibitor reacts with iron and form thin layer of oxide that protect the surface against corrosion attack.
Factor determining choice of chemicals
1. Previously oil based inhibitors was used but due to environmental and unfriendly it is not used . Nitride borate chemical are very effective against the corrosion and are most generally used . Nitrate is not compatible with galvanized steel. So galvanized coating piping in fresh water cooling system is prohibited .
2. So chromates are seldom used but not in fresh water generator they are check very popular in the past but if used in fresh water generator can cause holes in it ,for this chromate is also not used nowadays.
ADDITION OF INHIBITORs
1. Weight out the quantity of inhibitor specified.
2. Add the solution to expansion tank.
3. Run the engine for 24 hours to ensure that is stable protection of the cooling surface is formed.
4. Test using test kit for inhibitor concentration.
Cooling water test
=Test should be carried out onboard once per week to ensure minimum concentration level of inhibitors is maintained. Basically the inhibitors concentration ,PH value, chloride concentration ,should be in Limited as per guidance .
=PH should be from 7-8 and chloride must not exceed 50 PPM .
During dry docks cleaning of the cooling water system is done .
=Before starting the inhibition process- any existing deposit of lime ,rust or any oil sludge should be removed in order to improve the heat transfer and to ensure uniform protection of the surface by means of inhibitor.
The cleaning should compromise 1. Degreasing to remove sludge and 2. descaling with acid afterwards to remove rust and lime deposits.
cleaning agents
=slightly alkaline cleaning agent- degreasing process .
=for descaling with acid -citric acid, tartaric acid can be used.
1.Process of decreasing is
1. Use clean water for filling up the cooling water in the system can be used it does not contain inhibitor .
2. Heat the water to 60 degree and circulate the water .
3. Add the amount of degreasing chemical specified .
4. Drain to the lowest water level in the expansion tank .
5. Drain the system and fill up completely with clean tap water in order to flush out any oil or grease from that the tank .
6. circulate the water for 2 hours and drain again.
2. Descaling with acid solution same as FWG.
=Fresh water is used for cooling medium cylinder cover, liner, exhaust valve,turbocharger. 1.However acid and oxygen dissolved in water can corrode the surface 2.salt in water can form scales and impair heat transfer .
=Hence fresh water is used no salt only dissolved oxygen. A corrosion inhibitor additive is added to prevent corrosion. Most corrosion inhibitor reacts with iron and form thin layer of oxide that protect the surface against corrosion attack.
Factor determining choice of chemicals
1. Previously oil based inhibitors was used but due to environmental and unfriendly it is not used . Nitride borate chemical are very effective against the corrosion and are most generally used . Nitrate is not compatible with galvanized steel. So galvanized coating piping in fresh water cooling system is prohibited .
2. So chromates are seldom used but not in fresh water generator they are check very popular in the past but if used in fresh water generator can cause holes in it ,for this chromate is also not used nowadays.
ADDITION OF INHIBITORs
1. Weight out the quantity of inhibitor specified.
2. Add the solution to expansion tank.
3. Run the engine for 24 hours to ensure that is stable protection of the cooling surface is formed.
4. Test using test kit for inhibitor concentration.
Cooling water test
=Test should be carried out onboard once per week to ensure minimum concentration level of inhibitors is maintained. Basically the inhibitors concentration ,PH value, chloride concentration ,should be in Limited as per guidance .
=PH should be from 7-8 and chloride must not exceed 50 PPM .
During dry docks cleaning of the cooling water system is done .
=Before starting the inhibition process- any existing deposit of lime ,rust or any oil sludge should be removed in order to improve the heat transfer and to ensure uniform protection of the surface by means of inhibitor.
The cleaning should compromise 1. Degreasing to remove sludge and 2. descaling with acid afterwards to remove rust and lime deposits.
cleaning agents
=slightly alkaline cleaning agent- degreasing process .
=for descaling with acid -citric acid, tartaric acid can be used.
1.Process of decreasing is
1. Use clean water for filling up the cooling water in the system can be used it does not contain inhibitor .
2. Heat the water to 60 degree and circulate the water .
3. Add the amount of degreasing chemical specified .
4. Drain to the lowest water level in the expansion tank .
5. Drain the system and fill up completely with clean tap water in order to flush out any oil or grease from that the tank .
6. circulate the water for 2 hours and drain again.
2. Descaling with acid solution same as FWG.
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