FWG
Scale formation in freshwater generator can be controlled and minimized by continuous chemical treatment.
Poly-sulphate compounds (like sodium poly-sulphate) with anti-foam is preferred by marine engineers and is extensively used on ships. Their trade name is different, like:
- Vaptreat (by “UNITOR”)
- Ameroyal (by “DREW CHEMICALS”)
These chemicals minimize calcium carbonate scale formation and possibility of foaming. the compound is nontoxic, no-acidic, and can be used in fresh water generator producing water for drinking purposes.
Boiler water test
.bwt .boiler water
Alkalinity test/ pH value:
(9.5~10.5) Sodium hydroxide is usually added to maintain alkaline condition. (200-700ppm)
Chloride level:
Regular testing of chloride ensures the monitoring of any seawater contamination and any leak from aux condenser. (60-200ppm)
Phosphate level:
Sodium phosphate acts as water softener. They precipitate the scale forming compounds specially calcium sulphate from the boiler water to prevent scale deposit (30-50 ppm)
Conductivity/ hardness test:
Measured in micro siemens per cm. The reading determines the hardness of the water which is the TOTAL DISSOLVED SOLID (TDS)
Hydrazine level:
Correct dosage prevents oxygen formation. Max 50 ppm
N2H4+O2=2h2O+N2
Present chemicals used:
- Oxygen inhibitor
- Oxygen Control
- Oxygen scavenger
Standard Value for Boiler Water
Engine Cooling water Test:
pH value:
pH value should be kept at 7-8 at 25° C.
test cooling water every after 240 hours, add chemicals if pH value falls below 7.
If pH value goes over 10 , some amount of cooling water need to replaced.
Maintain pH value in alkaline range to prevent corrosive environment.
Nitrite (Anti-corrosive element):
Nitrite is used as an inhibitor to prevent corrosion in cooling systems. It promotes the formation of protective films on surfaces and inhibits corrosion by preventing oxygen-related corrosion. Nitrite levels should be checked frequently and treated with chemicals if levels are low. A common range for nitrite concentration is 500 to 1,500 ppm.
Keep nitrite value above 1500ppm.
Chloride content increasing:
→ Check possibility of seawater penetrating into cooling water.
→ Check the system which includes sea water, for example fresh water cooler cooled by sea water.
pH value decreasing or sulphate content increasing:
→ Check if cooling water is contaminated by exhaust gas.
→ Check cylinder head by hydraulic pressure test.