Aalborg Auxiliary Boilers leaking water into drum

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Ufok
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Aalborg Auxiliary Boilers leaking water into drum

Post by Ufok »

Good Day!

I work as a 3rd Engineer onboard a DFDE LNG carrier equipped with 4 exhaust gas economizers and 2 auxiliary boilers. After joining the vessel, I noticed that despite complete isolation of the main feed water inlet valves (4 valves for each boiler), auxiliary feed water valves (2 valves), warming steam (1 valve) and condensate inlet from economizers to aux boilers (2 valves) the boilers are still gaining water. For the Port boiler about 5 cm per day, Stbd even 50 cm per day. The economizers are at 11 bar pressure, working boiler at 10.2 and the completely isolated boiler, even with warming steam shut, goes up to 7.8 bar and stops gaining pressure, but the water level keeps on rising

I suspect that the condensate inlet valves, going from the economizers into the boilers are all passing, but it might also be the auxiliary feed water line. The main feed has 3 globe valves and 1 automatic valve, I doubt all 4 valves for one boiler would be passing.

Has anyone encountered a similar issue?
To troubleshoot this properly I would need to shutdown the whole steam plant and the vessel schedule does not allow that for now.

Any input would be greatly appreciated!
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Merlyn
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Re: Aalborg Auxiliary Boilers leaking water into drum

Post by Merlyn »

Test points?
Test kits?
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Ufok
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Re: Aalborg Auxiliary Boilers leaking water into drum

Post by Ufok »

No way any test points are leaking into the boiler. The only dosing tank is 50 liters, has to be manually started and doses around 30 liters par day, way less than the boilers are gaining in water level per day.
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Re: Aalborg Auxiliary Boilers leaking water into drum

Post by popeye62 »

Hello Ufok. I have never worked on a gas carrier but I don't think it is relevant here. How was this issue first discovered, were you having to blow down the boilers more often? Is the boiler over-filling when hard steaming (all four econs/engines running)? Is there an increase or decrease on the flow counter into the hotwell/cascade tank i.e. the boiler water consumption? When you isolated the feed into the boilers did you stop the feed pumps or just let them discharge back to the hotwell? I don't know why you would isolate the returns from the econs as that water is boiler water and part of a closed system. Are the econ circ. pumps off as, obviously, that water is going to drop back into the boiler.
What are the conditions you describe above i.e. are you alongside with the boiler flashed and modulating normally around 8b? Presumably you have one (?) generator running; is there enough load to generate steam from its econ?
Is the auxiliary feed line from the same feed pump but by-passing the control valve?
Most of the usual suspects (dump condenser, drains cooler, evaps, feed pump cooling etc) where steam meets water would tend to fill the condensate system and end up in the hotwell, over-flowing it and reducing the boiler water consumption to zero but would not enter the boiler so that suggests that the water is through a direct connection on the shell. Regarding the isolations, I have given and received a few bollockings for using a wheel key to close valves (they are only for opening valves) but I did find that valves, even new valves on the steam and condensate system did need a really good nip for a proper isolation but don't go mad.
Has the quality of the water changed? it would give us a clue as to the type of water.
So you don't have an auto dosing treatment system (Aquanet type)? They have a flushing cycle but the sample cooler is a regular failure.
When you say a completely isolated boiler do you mean steam as well e.g the main stop is shut? and the level still rises but the pressure stays at 7.8b. That sounds like steam is condensing in the isolated boiler which is passing through the NRV provided that the main stop is open or passing but I am speculating.
Good luck, John
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