Stopping and Depressurising Procedure for Marine Boilers

     Stopping and Depressurising procedure for Marine Boilers        
            Boiler needs to be stopped for various reasons like maintenance, survey etc. Depressurising the boiler is a lengthy procedure, before depressurising please read the manual and risk assessment that is to be taken. 

Here you will get a vague idea about boiler depressurising.
> Change over FO to Do, all systems like ME, AE and Boiler. Because with out steam you cannot use HFO
> Turn the switch in to stop position, boiler will automatically stop after post purging. (If it’s required ,purge the furnace manually)
> Close main steam stop valve
> Stop the feed water pumps and fuel oil circulating pumps. If there is heater for fuel oil, stop it.
> Make sure that vessel is not in loaded condition. If its loaded there is a chance of sea water flowing back to the boiler while blow down
> After completing the change over, stop EGB circulating pump and close the suction side valve from boiler and discharge side valve to Boiler
> Open the vent for EGB
> Stop the boiler and stop boiler feed water pump
> Close the valve for feed water controller
> Isolate DP transmitter by opening the equalizing line and closing inlet-oulet lines
> Start blow down the boiler until low low water level alarm comes
> Let the boiler pressure comes to 2 bar
> Make sure that boiler body temperature coming down gradually
> When the drum pressure come to 2 bar open the vent
> Wait until the pressure comes down to 0-0.2 bar
> Start draining rest of the water if required give pressurized air through air vent so that all water will get drained out.

You Can Answer Following Questions,
> How to stop the boiler
> Procedure for depressurising the boiler
> Why it is difficult to drain the boiler if the vessel is in loaded condition
> At what pressure you should open air vent while depressurising boiler
> How do you prevent vacuum generating inside the boiler while stopping the boiler?

If you know more or have doubts please comment below

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