The document provides guidelines for maintaining a fresh water generator (FWG) on a vessel: 1. Check the salinity alarm monthly to ensure only fresh water enters the fresh water tank. 2. Stop the FWG when approaching contaminated waters to prevent bacterial infection. 3. Open the separator shell and inspect for scale during scheduled maintenance or if production drops. 4. Clean the heating tubes twice a year or when production drops to prevent scale buildup.

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Fresh Water Generator maintenance
What are correct maintenance practices for Fresh Water Generator?
Always give a priority to the Maker's manual. Following guidelines
should be used as reference only.
1. Check Salinity Alarm
The salinity alarm or salinity indicator needs regular checks as it allows
only pure fresh water to flow into the fresh water tank and critical for FWG
operation. The electrodes of salinity alarm must be cleaned on monthly

2. basis to remove dust or scale deposits. Alarm settings must be verified
before putting the Fresh Water Generation system into operation after
cleaning.
2. Stop Fresh Water Generator properly and at a right time
When a vessel approaches a port, land or estuary, the Fresh Water
Generator must be stopped as at such places the sea water is heavily
infected with bacteria and contaminated.
3. Open Separator shell as per PMS or when production drops
The separator shell and heat exchanger covers can be opened up and
inspected during scheduled inspections for scale formation or if cooling
tubes are fouled with any sludge formation. As per recommended in Safety
Management System Manual or Flag State Requirements, the Fresh Water
Tanks are generally cleaned once in six months or on yearly basis.
4. Clean the Heating Tubes as per PMS or when production drops
Cleaning or descaling of the inside of heating tubes should be made
twice or three times in a year physically or dissolved by chemical methods.
Scaling can be prolonged by not operating the plant at contaminated water
areas such as in harbors or ports.
5. Use scale inhibitors

3. Scale inhibitors are used to prevent scale formation by dispersing scale
deposits and delaying reaction. This also prevents scale deposits from
adhering to heat transfer surfaces. Scale formation inside heat exchanger
requires cleaning if specific temperatures cannot be obtained for inlet and
outlet of fresh water.
6. Repair damaged coating
In case coating inside the fresh water generator is damaged, the
damaged covering is to be scraped off and the surface should be then
thoroughly dried. After putting the undercoat on the steel surface, epoxy-
resin or food coating (as prescribed by FWG manufacturer) is to be applied.
7. Inspect Impeller Periodically
The impeller of ejector pump wears out and its surface also gets
damaged due to high-speed revolution. This is inevitable due to continuous
operation of the pump. The condition of the impeller should thus be
inspected periodically.
8. Keep the FWG daily production log
The FWG production log is very important for early detection of
production drop which means that Fresh Water Generator requires cleaning.
9. Monitor the FWG vacuum

4. If vacuum inside the FWG decreased this may indicate the worn ejector
pump or insufficient sealing of the casing.