PROCEDURE FOR STARTING F.W. GENERATOR ON SHIPS

PROCEDURE FOR STARTING F.W. GENERATOR ON SHIPS

Water is an important commodity out at sea and hence the F.W. generators need to be started as soon as the ship enters open sea. Find out the method of doing this

INTRODUCTION

A ship normally sails on long voyages and certainly drinking water is one of the most vital elements required on board. If you are thinking that this should not be a problem since the oceans contains unlimited water, read this article on the effects of drinking sea water. Especially imagine the condition in areas such as the Dead Sea, hence a provision for converting salt water to fresh water exists on ships and the machine is known as the fresh water generator.

We have learnt about the machine and its working in our previous articles but it is a different thing to know how and when to start these water generators on a ship. This article will tell you exactly the same and first we will see if it is OK to start these water generators anywhere.

Well I must tell you that a fresh water generator can only be started when the ship is 12 nautical miles away from the port and after sea speed is given to the main engine from the bridge .And when all the temperature and pressure parameters are normal and main engine is on sea speed and not in congested waters, or not manoeuvring.

STARTING OF FRESH WATER GENERATOR

Normally a Junior Engineer would be required to start the water generator once the above conditions have been achieved. Many JEs are not quite familiar or comfortable with this simple procedure, so just outlining the main points here.

1. Check the jacket cooling water temperature outlet from the main engine – it should be constant

2.Open the Ejector pump suction valve and discharge valve to OBD (over board)

3. Close the vacuum breaker valve

4. Open cooling sea water valve inlet to condenser and out let valve

5. Check salinometer (salinity indicator) and distillate pump

6. Start the ejector pump and maintain the pressure more than 5kg/cm2

7. Check for the vacuum inside the shell as slowly rising

8. When the vacuum gauge reading reaches about 17mm of mercury, open the feed water to heating tubes

9. Check through the sight glass and maintain the water level inside the shell

10. Open the jacket water inlet valve fully – out let valve to be throttled

11. The jacket cooling water circulating through the spaces outside the heating tubes causes vacuum to drop, shell temperature to rise and feed water level to fall

12. When all the above is stabilized to normal, steam starts rising through the demister units and get condensed in the condenser

13. Fresh water gets collected in the catcher plate which can be seen through the gauge glass

14. When the gauge glass level is more than 3/4 th, put the salinity indicator to ‘ON’ position

15. Drain the water to the bilges or send it to the feed system again till the salinity level comes to set value (5-10 ppm)

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 outlet

18. Check for the tank vacuum to stabilize after some time, and ensure that the shell temperature should not raise more than 40-45o c

19. Observe all gauge readings of:

• Inlet and outlet temperature of jcw
• Condenser sea water inlet and out let temperature
• Feed water level inside the shell

20.Distillate level in gauge glass should be monitored and always maintained at half gauge glass level when the distillate pump is running.