New Crude Oil Storage Tank Floating Roof Membrane Rectifications 1

[786392]

Dear Forum Colleagues,

At one of the upcoming Refinery Installation,apology if inappropriate forum.

An (External) floating roof membrane recently fabricated has extra ordinary unevenness.

Expert comments/suggestions for removing the fault at the earliest with minimum extra work are welcomed.

Also request guidance on applicable codes for repairs/extent judgment.

Aboveground Crude Oil storage tank shell erected as per API650. Tank's Diameter is around 68 meters, commissioning needed soon.

Request help& guidance on how urgent repairs/remedial action to initiate?

Best Regards
Qalander(Chem)

 

[IFRs]

Uneven membrane is not unusual. There is no code that I know of that specifies a maximum. How uneven is it?

 

[786392]

Thanks IFR;

Definitely you,Joe tank,gr2vessel and other versatile/skillful forum giants are requested/invited to guide.

Since there are 25 plus depressions forming pools if water etc. gets accumulated.

Such pools;varying sizes and Hap-Hazard patterns and dimensions 12'X15'~ 25'X31' etc. with apparent pool depths 3"~5".

Hope this gives a general outlook,I don't have snaps handy to share right now.

Best Regards
Qalander(Chem)

 

[gr2vessels]

786392,
I am humbled of including me with the giants of this forum, but I got news for you;- I lost almost 30# in the last 12 weeks and I hope for another 20 in the near future. I love it and determined to keep it that way.
As far as your tank concerns, you seem to be right, in case of rain there could be significant additional weight and the risk of imbalance of the roof. However, there are many solutions for this, starting with displacing the deeps with highly adhesive foams (liquid sprayed on the affected area which expands to hard foam in contact with air), forcing the water to run towards the drain, building an umbrella type of structure and covered with UV resistant plastic over the affected area (or part of area, depending on the acceptance level of the defects area), welding thin metal sheeting over the affected areas, using also light gauge purlins like supports). I personally would sue the contractor to bear underwear to have him repair the bad job he did. Depending on the proximity of those affected areas, you could drill holes and weld in new drain holes linked to a manifold drain collector suspended under the roof in the liquid space and attach a flexible drain hose to the main drain pipe. Obviously, this seems to be over your head as far as the design concerns, so you need a qualified tank designer to take responsibility for all the above solutions, all implying additional engineering not necessarily covered by the API650.
Please come back with more questions you (hopefully) might have, in order to assess better the whole picture and to give you the chance of making a more educated decision on your headache.

Cheers,
gr2vessels

 

[786392]

Splendid! gr2vessels,you hit the problem right on the head.

Yes,We are confronted with this typical problem and any remedial to obviously hurt/affect Floating Roof Buoyancy and severely impact its useful Service/Life.

Any snapshots if manageable will be shared for generating further guiding help.

Just a little query,has API620 any applicability on this matter or any other relevant code/recommended practices?

Thanks in advance

Best Regards
Qalander(Chem)

 

[IFRs]

Except for a double deck type EFR, I have never seen an EFR that did not have some undulations to the membrane. Overall buoyancy should not be a problem as they are designed for 10" of water. When are the undulations present - when on the supports or when floating? The "apparent pool depths" may be less than estimated if someone is looking from the tank top down. While you may have a problem that needs attention, you may not. The membrane will not have a uniform slope to it especially when floating and there will almost always be some low spots where a little water accumulates.

 

[786392]

Dears,
1) Please correct reporting of above 2nd post (19th Feb 09 0:35)
Actual depression's depth is approx. 2.5"~3" instead of 3"~5" 2)

2) Snapshots are managed/ being attached

3) Dear IFR, I do know that EFR Buoyancy by Design to be capable to keep it afloat even

(a) With 10" rainwater accumulation on membrane surface and

(b) Having its 20% Pontoon’s in damaged& filled/ topped up condition

The main concern remains unevenness evident while tank's membrane is resting on support legs.

Await any more helping suggestions for corrective course of action.


Best Regards
Qalander(Chem)

 

[Medaney]

salam alikom.
i'm new to this kind of conversations.
i work in a crude oil terminal. we have 16 tanks of 100,000m3 capacity.
concerning your reported article.
1st i wanna assure you that this is a commonly known fact that is found in many tanks.
the idea of filling these ponds with foam is a good idea if u can make sure water will not penetrate under that foam and stay there longer than wanted and may harm the coating of the roof.
i advice u after reviewing the pics to do nothing for it is very minor problem.

 

[MACARTHUR]

Just a small contribution to this...

1- Yes if your skin and pontoon roof is designed as per API standards, no way to worry about
2- A skin is suposed to ''float'' on stored productand eneveness is common and normal
3- What I would worry about is correct sizing of main drain system in case of heavy storms / Also make sure the inlet/outlet product diffusers avoid any strong turbulences in tank and make the EFR unbalanced and unstable / To have correct smooth, good centering and annular gap tolerant free seals system to avoid the EFR to sink...

In conclusion, best but expensive solution would be a lightweight geodesic dome over and yu can get rid of water once and for all...