The fresh water generator should be fired up once the above regulations and requisites have been achieved; using the guidelines listed below.
A sketch showing the various components is shown below and can be referred to when reading the guidelines.
1. Check the jacket cooling water temperature outlet from the main engine - it should be constant
2. Open both the ejector pump suction valve and the overboard discharge valves.
3. Close the vacuum breaker valve
4. Open main sea water feed inlet valve inlet and discharge valves to and from the generator condenser; (the seawater can also be supplied from a stand-by sea water pump; if this is to be used instead, open the pump main inlet and discharge valves and start the pump)
5. Check salinometer (salinity indicator) and distillate pump operation
6. Start the ejector seawater pump and maintain the pressure of 5kg/cm2 or higher
7. Check that the vacuum inside the shell is slowly rising as the ejector removes the air from the unit.
8. When the vacuum gauge reading reaches about 17mm of mercury, slowly open the seawater feed to heating tubes.
9. Check the seawater level inside the shell through the sight glass and adjust this water level using the feed inlet valve.
10. Once the heating coils have been covered with seawater; open the jacket water inlet valve slowly to the full open position whilst throttling back the jacket water outlet valve.
11. The effect of the jacket cooling water circulating through the heating tubes causes the shell vacuum to drop, its temperature to rise and feed water level to fall.
12. When all the above is stabilized and running normally; the seawater starts evaporating and steam can be observed rising up through the demister units to be condensed by the condenser coils.
13. Once condensed, the fresh water droplets fall downwards to be collected in the plate collector tray. This can be witnessed through the sight glass
14. When the gauge glass level on the plate collector is more than ¾ full, put the salinity indicator to 'ON' position.
15. Divert the processed water to the bilges or return it to the feed system again till the salinity level comes to the required set value of 5-10 ppm (Parts per million)
16. When the salinity level comes to set value, open the discharge valve of distillate pump to the fresh water tank through the flow meter and start the pump
17. The evaporation rate can be increased by throttling the jacket cooling water return outlet
18. Check for the tank vacuum has stabilized.
19. Observe the following gauge readings on a regular basis;
- Inlet and outlet temperature of jacket cooling water
- Condenser sea water inlet and out let temperature
- Feed water level inside the shell
- Distillate level
- The salinometer is designed to alarm, automatically shutting the freshwater discharge valve to the storage tank, and dumping the distillate to bilge when maximum salinity is exceeded. It is always best to check the diverter valves are all operating as these can stick due to heat/coating of salts.
- The distillate level in gauge glass should be monitored and always maintained at half gauge glass level when the distillate pump is running
- Remember to check the main engine jacket water cooling temperatures once the freshwater generator has settled down.