CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

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adreno1981
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CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

Postby adreno1981 » Fri Mar 23, 2018 10:13 pm

Hey fellas ,
In case Heavy oil gets carried over to boiler and cascade tank in a big quantity overnight on a UMS Ship, manual cleaning and chemical cleaning by circulation can be done to clean surfaces after isolating the system and rectifying the cause of oil leak. Has anyone ever experienced the same , and can anyone brief on the name of chemicals that can be used for cleaning in step by step manner after manual cleaning..Also, what can be done to restore boiler water condition to its optimum condition. ..any help on the matter will be highly appreciated.
Thanks
brgds

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Big Pete
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Re: CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

Postby Big Pete » Sat Mar 24, 2018 1:47 am

There should be an oil content monitor fitted to the cascade tank on an UMS ship, this should be regularly tested and if it is not working the ship should not go UMS but be operated manned, with regular checks of the cascade tank and any other systems where the alarms and automation are not working correctly.

You do not say if this is an auxiliary steam plant or for main propulsion, but either way oil in the boiler can cause localised overheating and boiler tubes to burst, extremely dangerous, so the Boiler should be shut down or run at lowest possible power and pressure as soon as the oil contamination is discovered. Depending on the overall safety of the ship.
Minimum No of people should remain in the Boiler/ Engine Room in case of a Boiler explosion.
There should be a skimmimg connection on the cascade tank to skim off oil from above the water this should be utilised to drain off all the free oil from the cascade tank.
The source of the oil contamination should be found and isolated.
As soon as it is possible to shut down the Steam plant any ordinary detergent can be circulated through the Boiler and feed and condensate system to remove any free oil. The Hot well filters should be replaced.
Any oil that has gone into the boiler is likely to have been carbonised, and will have to be removed with Carbon Remover or by manual cleaning.

Something like this will be a Major Insurance claim and you should involve Superintendents, Class, the Boiler Makers and the your Chemical supplier for detailed Technical advice, and support, all as soon as possible. Expect to be laid up in Port for a while while all this is done and a full Boiler Survey carried out to ensure that all the oil has been removed and no damage done, (Hopefully) if not, to decide the extent of repairs required and to carry them out, followed by pressure testing etc.
I hope that this is an exam question and I would warn that I do not have a steam ticket so I would consult with others first, before using my response as the basis for answering an exam question. If this is happening to you now then GOD LUCK and keep safe.

BP
It is always better to ask a stupid question than to do a stupid thing.

adreno1981
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Re: CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

Postby adreno1981 » Sat Mar 24, 2018 1:58 am

hey Big Pete ,
Thanks for a prompt reply..Highly appreciate your response to my query wrt aux steam plant.
brgds

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D Winsor
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Re: CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

Postby D Winsor » Sat Mar 24, 2018 4:35 am

What type of boiler is it, water or fire tube because depending on the configuration it may require a major overhaul of the boiler to get all the residual fuel out of the boiler.
The reason I asked is that I experienced a situation where blended fuel and diesel had made it's way into a vertical fire tube Spanner boiler/Exhaust Gas economizer system. The fuel, both heavy & diesel, made it's way into the system through a failed Engine fuel supply heater. Despite measures to minimize the amount of fuel being dumped into the condensate system when changing between heavy and diesel fuels. Fuel would overwhelm the cascade tank and hot well when the steam pressure in the heater was lower than the fuel pressure. After the failed heater was replaced the boiler was cleaned with disbursement chemicals and everything went back to normal. Later after cleaning the tube plate inside the firebox cracks were found in the tube plate between the tubes at the center of the boiler. This then turned into a major repair when tubes had to be removed so to facilitate removal of the collected fuel residue from the tube plate before it could be repaired.
It was surmised that the heat of water was enough to crack the lighter product out of the blended fuel and was carried out of the boiler with the steam leaving the residual fuel behind. The boiler maintenance and cleaning chemicals along with other contaminants reacted with the fuel making it heavier than water and caused it to settle on the bottom of the boiler. The fuel as it settled was circulated with water flow of the economizer circulating pump to the center of the tube nest, resting on the tube plate above the fire box and directly in line with what would have been the highest heat concentration zone for the burner. The settled fuel then created an insulating layer around the base of the tubes which lead to the cracking of the tube plate.
So if you have a similar type of fire tube boiler, regardless of how much or how little fuel made its way into the boiler, I would be looking very closely at the tube plate in the firebox for cracks.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

Ravi Viknesh
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Re: CARRYOVER OF FUEL OIL TO CASCADE TANK AND BOILER

Postby Ravi Viknesh » Thu Aug 16, 2018 11:15 pm

Hello everyone! was reading this post for the correct procedures which should be followed when we find oil in the boiler system onboard. I read the previous comments and I really appreciate the knowledge that is shared and it really helps juniors like me.

I do have a question.. I have heard about scum blowdown of boiler for few times along with the above procedures that is mentioned over here when we find oil in the system. I just wanted to know can we really do that? because of the MARPOL regulations. If that can be done.. How?. If not.. how the oil which reached the boiler can be removed prior to manual/ mechanical cleaning.

It would be great for juniors like me to know about correct procedure that should be followed.

Thanks in advance!


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