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