restoring condansate tank 1

[mustafa2014]

dear all,

good day

we have faced a problem n our gas plant, when our fair team was doing a test to the hydrants over the tank.
the roof was fall of water over it , which cause skewed to the roof and that's lead the condensate to escape over the roof. Could any one explain or guess the reason??

even more we are going to restore the tank, have any one a scope of work should be done or any tasks should we consider??please send to us

many thanks for your cooperation in advance

 

[Tmoose]

Hi Mustafa,

Is your question how the water/condensate got there, or why did the roof deflect, or adopt a "pitch" that was not there before?

 

[LittleInch]

Send photos.

I can see English is not your first language, so add photos and sketches as your explanation is difficult to understand, but it sounds like the roof has partially failed.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[JStephen]

Was this a floating roof that failed due to being flooded with water?
Were drains open? Were they adequately sized for the flow?

 

[mustafa2014]

thank you all for your reply,

I will try to explain to you,

before one week, our operators saw that the condensate escaping from the roof and flooded out of the tank. when went up to check the roof the founded Slightly sloping. they thought that sloping because the drain of the tank was failed (plugged), it could be that happen?.

I have see a lot of corrosion on the internal wall of the tank, so is that corrosion cause that problem when the roof moving up and down??

I hope that is clear enough.

 

[LittleInch]

Mustafa, unfortunately it is not clear at all. You appear to have a floating roof which has tilted or partly sunk. This could be for many reasons, but a blocked surface water drain is one reason, but if there is lots of corrosion for some reason, the roof float might be damaged. Also if your product is very volatile, you nigh have created a vapour pocket under the roof which caused it to tilt.

Who knows, you have provided no information, no drawings and no photos. Seems all the details you can, add a diagram and some photos and ask some particular questions. Remember we can't see anything from here so can't see the size, the damage, the vapour pressure of the liquid, the corrosion, the inlet and outlet flowrate etc etc

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mustafa2014]

dear Mr,LittleInch (Petroleum),

thank you very much for you kind reply. you find attached the failure report for that tank an a pictures for it.

this report I think is quit poor and not enough, what do you think??

please check the attachment.

thank you in advance for your help

 

[LittleInch]

Not a bad report in my opinion. The thing that is missing is a proper description of the water drainage system, size etc, and what the design documents say about what the water drain was designed for (maybe lost by now, but worth a search of the records). Also how much water was it possible to pump from the rim hydrants? It is entirely feasible that a blocked drain could sink the roof especially if the water from the hydrants went on for 5 hours !!!. You get some heavy rain in N Africa, but not that heavy so it's difficult to blame the designers.

Your issue now is that the roof has sunk without being prepared properly by having all it's legs down. This could lead to internal damage to the roof, especially the pontoons or any internal pipework and also maybe the seals if the roof has gone down too far.

What you need to do is pump out all the water on top of the roof, add water slowly to the tank to re-flaot the roof, put all the legs down, drain the tank again and get inside and inspect it. You might have damaged the pontoons under the roof, but otherwise it looks in good condition from the photos supplied.

I'm not sure why your operator allowed the fire pumps to continue spraying water into the tank for any longer than 5 minutes without someone going to see if there actually was a fire. most fire and gas systems I see now work on the basis of not actually doing anything until it gets "confirmed fire", either two sensors going off or a manual push from someone with eyes. Maybe need to think about how your system responds to fire warnings in in the future.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mustafa2014]

dear Mr.LittleInch,

I am really thank you very much.

I would like to notify you that the internal wall (shell ) of the tank is really corroded.

this also I think strong reason to damage the seal and one of the reasons to this problem??

 

[LittleInch]

Its difficult to see from the report so may need some more close up photos, but just looks like superficial surface rust to me - Looking at the big photo where the rust streaks are below each of the spray nozzles, it looks like they have all been leaking a lot.

I can't see it being a big problem for the seals, but again you need the seal vendor to come and inspect it if you think they need repairing or replacing

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mustafa2014]

dear sir,

I am really appreciate your help

many thanks

 

[LittleInch]

Reading this again, I think your seals are probably working very well. If they hadn't been the water could have flowed into the tank and left the roof floating, but instead the water has built up on top of the tank so much that the roof has sunk.

The biggest question is whether the pontoons under the roof are full of water or air - they need to be full of air otherwise your roof will never float again. You're going to need to remove all those manholes on the outer rim of the tank and pump the water out (if any).

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mustafa2014]

dear sir

the pontoons are fall of water as you can see in photos.

so we need to pump out the water?

 

[LittleInch]

Yes

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[IFRs]

The roof drain was open which allowed condensate to flow into the dike area. Question - was the roof drain open when the tank was deluged with water? If not, that's why it did not drain. If it was open, maybe the water coming on to the floating roof simply came on faster than the drain could release.