Tank Collapse
Tank Collapse
(OP)
I have just witnessed collapse of API 650 HFO tank because of very harsh wind effect in erection situation. it was collapsed at the last course of shell. The top of tank was open. Wind velocity is 160 km/h at site and tank is located near seaside. However tank was safe according to the min. requirement of intermediate wind gird namely H1>H and there was no need to put a wind girder.
Tank was subject to vacuum effect because of wind and collapsed. So what is your comment to this issue. What should have been done to prevent from this event?
Tank was subject to vacuum effect because of wind and collapsed. So what is your comment to this issue. What should have been done to prevent from this event?





RE: Tank Collapse
Was the tank fully assembled and in place?
What size tank?
Was it on a crane? Sloped? On a support?
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Tank Collapse
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Tank Collapse
What type of roof? internal/external floating, Fixed?
How was it subjected to vacuum?
I have just witnessed the exact same thing after Hurricane Gustav. We have a 150' diameter x 40' high fixed roof tank. Not sure EXACTLY what the winds were, but estimate around 75-90 mph. We were in the process of replacing the entire roof and rafters due to corrosion. being a fixed roof tank, it didn't require an intermediate wind girder. We came back from evacuation, and the tank had collapsed on one side. it put a nice KINK in the shell.
RE: Tank Collapse
Joe Tank
RE: Tank Collapse
RE: Tank Collapse
JStephen... That's the first question i asked. "what happened to the guy lines?" apparently, the repair company didnt use any. Instead, they built a scaffold around the top course. That didnt do much.
Check out the pictures below. in the pictures, they've already removed the scaffolding in the damaged area, but you can see it around the rest of the tank.
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RE: Tank Collapse
In all Fairness if a tank is under maintenance/repairs in roofless condition then,either additional temporary safeguarding through especially welded eyes all along upper circumferential shell span be provided alongwith steel slings fastening to secure, or
There should have been special windgirder re-inforcements in-place on upper portion to counter possible foreseeable extreme stresses impact from very high wind loads described above.
Hope this Helps
Best Regards
Qalander(Chem)
RE: Tank Collapse
Thanks a lot for your comment. Guy wire precaution had been taken while erection from several joints but stiffening scaffhold. Nonetheless, this collapse occured.
RE: Tank Collapse
RE: Tank Collapse
I wonder if we had executed all precautions together guy wire ,hole and stiffening ring , would have tank been safe against vacuum effect by squeezing as a paper?? this is exactly a case study. Maybe sometimes engineering is not adequate. what do you think?
RE: Tank Collapse
RE: Tank Collapse
RE: Tank Collapse
However provision of some additional stiffening ring/ Windgirder as per special circumstance could have helped; since a roof less tank is quite similar in nature and response to a 'Floating roof Tank' and as such very difficult to sustain the described high wind load conditions otherwise.
Definitely it should be the mechanical disipline guys to come forward with better suggestion/ remedies.
Best Regards
Qalander(Chem)
RE: Tank Collapse
RE: Tank Collapse
RE: Tank Collapse
How wide are the shell courses? The second shell course from the top looks very narrow. API-650 rerquires a minimum of 6 ft (1.8m) wide. Also, how is the roof structure being stabilized?
Joe Tank
RE: Tank Collapse
The Photograph's close-up show that post damage conditions of all courses sheets are not of the same color and appearance;
as if there was some variation in the steel sheet's material quality used in fabrication.(can not say how much&how far?)
Best Regards
Qalander(Chem)
RE: Tank Collapse
"API-650 rerquires a minimum of 6 ft (1.8m) wide." this is not strict as i know. All shell courses are in same material quality undoubtedly.
RE: Tank Collapse
RE: Tank Collapse
I'm not exactly sure what you meant about "not as strict as I know". But, I did re-read API-650 about course width and it does permit narrower widths by agreement with the purchaser. The contractor may not make the decision to use narrower widths solely on his own.
Joe Tank
RE: Tank Collapse
I do not think one can judge steel plate quality by a photograph and certainly not by the variation in mill scale presence on the plate surface. I have never heard of appearance as a factor in plate quality. Only material testing could reveal such conditions.
Joe Tank
RE: Tank Collapse
Could you please show a way how i can calculate stiffening scaffold or a provisional stiffening ring section area while tank is open-top during erection to prevent from bending of plate against harsh wind or vacuum effect.
For instance, for 5000 m3 tank(Diameter=25m , Height=12m) is 140UNP ring adequate if it is put throughout circumferance in the middle of tank inside?
Wind velocity =160 km/h appr.
Thanks in advance for help.
RE: Tank Collapse
Joe Tank
RE: Tank Collapse
I believe Joe's advice is Master advice indeed.
Any open top tanks as per API 650;as is the case for floating roof tanks with open tops.
Wind girders and adequate stiffening rings are mandated to retain/ maintain the shape.
Best Regards
Qalander(Chem)