Stiffener between shell and bottom in storage tank 1

[Capely]

I am technical engineer at petroleum products storage plant in La Reunion
We have 3 storage tanks built in 1960 and 1961 according to SHELL company standard
I have no technical documentation about these tanks
Inside tanks ,about every meter of circonference there are stiffeners looking like L welded on the shell (1.5 m height) and the bottom of the tank (1.5 m length)
At the construction the tanks were fitted with pressure and vacuum relief valve (Varec).
Now we have atmospheric events
I suppose that these stiffeners have been placed for strengthening the link beetween shell and bottom due to presence
of relief valve
I have to remove the old bottom plates and with them horizontal part of stiffeners
I think now it is not necessary to put again on the new bottom plates these stiffeners

 

[hydromarine]

Whats the diameter of the tanks

 

[Capely]

Good day

Thank you for your reply

tank n°13 diameter 7.65m shell height 7.76m
tank n°11 14.63m 9.30m
tank n°12 19.51m 14.82m

Best Regards

 

[hydromarine]

Have a look at API 650 (you probably have already) personally I would rebuild with stiffeners as in the original build , why are your thoughts not to include the stiffeners in the rebuild

 

[Compositepro]

It looks to me that the stiffeners are intended to resist sloshing loads like you see in an earthquake.

 

[saplanti]

I can think of the following in addition to above:

1. Shell might be restrained against buckling and wind all together by vertical stiffeners,
2. The stiffeners might be working against the bulging effect on the shell close to bottom plate. see the stiffeners to increase the bending moment capacity.
3. Stiffeners on the bottom plate might be providing even load distribution on the foundation. You need to check foundation details.
4. There might be an event, such as an earthquake, in the past caused the buckling on the wall and tbey decided to support the shell bt this simple method.

In case you are going to put new one you had better to design it to the new code rules which may not be requiring those by increased wall thicknesses.

Regards,

Ibrahim Demir

 

[11echo]

One of the common ways tanks fail (other then corrosion) is something called an "elephant's foot" (see attached pic). I beleive your original stiffener design is to fight that failure. You might want to re-think not using them.

 

[BigInch]

I doubt that there is anything having to do with relief valves in the design of stiffeners. Without stiffeners there, you have no moment carrying capacity between the shell and bottom beam, no shear capacity for transfer seismic slosh loads, or wind loads, from shell to bottom, no reinforcement from buckling of shell due to weight of shell above. The beam could be reinforcing against excessive radial loads. It looks like somebody thought that it was needed before, so you should have a good reason to remove them and be able to prove that you can do it without ill effects. Why don't you think you need them now? A 14.8 meter high tank is nothing to play engineer with. Where's your calculations to back up your position that they these stiffeners are no longer needed, or is that simply your opinion. What's the stress at the base plate. Any idea? In the meantime, hopefully the wind doesn't blow and all your earthquakes for this year are over and done with.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[IFRs]

On the other hand, there are literally thousands of tanks just like yours without such stiffeners all over the world. They do just fine. The question is, why do your tanks have them? What makes your situation so different? What are your foundation conditions, what are your product, wind and seismic loads? If you were to build a new tank, how would you do it? Were these overkill for some condition that we really don't worry about any more? Oh, and is that a Petrex aluminum IFR?

 

[BigInch]

located above hotspots in the Earth's crust. The Piton de la Fournaise, a shield volcano on the eastern end of Réunion Island, rises more than 2,631 metres (8,632 ft) above sea level and is sometimes called a sister to Hawaiian volcanoes because of the similarity of climate and volcanic nature. It has erupted more than 100 times since 1640 and is under constant monitoring. It most recently erupted on 2 January 2010.[10] Before that, the most noticeable was during April 2007, when the lava flow was estimated at 3,000,000 cubic metres (3,900,000 cu yd) per day.[11] The Piton de la Fournaise is created by a hotspot volcano, which also created the Piton des Neiges and the islands of Mauritius and Rodrigues.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky