Floating roof. Joint between pontoon and deck design

[PINTAIUS]

Hi to all the colleagues in the forum.

I am designing a floating roof for a customer (single pontoon type), and I have suggested the junction between the deck and the pontoons as I always do (see the sketch, TYPE B).

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Today in the morning I have receipt an e-mail from the customer, telling me that they want to change the design suggested by me to another (see the sketch, TYPE A).

I have seen this type of floating roof (The TYPE A) in old tanks, but I always considered that the stress in the deck was bigger than in the other type, due to push from the product once the roof sinks.

I mean, in the "Type B" see the sketch I have drawed (sorry for the quality), the roof sinks until it reach the balance (thanks to Archimedes), and the deck receives less torque from the pontoons.

I think in "Type A", the push from the product onto the deck has a bigger value than in the other.

Anyone could help me in this question?


Thanks in advance and best regards.

[sadane]

Dear PINTAUS

I think the type A is better because the whole roof rests on the liquid, while in type B it may have gazeous interface between the deck and the liquid so that the weldings will suffer more stress.

[sadane]

Dear PINTAUS

I think the type A is better because the whole roof rests on the liquid, while in type B it may have gazeous interface between the deck and the liquid so that the weldings will suffer more stress.

[babyfatface]

Type B develops a vapor pocket.

[PINTAIUS]

That is the reason of my doubt.

In one hand, we have less stress onto the deck (TYPE B), but in the other, we have the risk (more than a risk, I think it will be a fact) of the vapour.

Thank you very much.

[PINTAIUS]

That is the reason of my doubt.

In one hand, we have less stress onto the deck (TYPE B), but in the other, we have the risk (more than a risk, I think it will be a fact) of the vapour.

Thank you very much.

[Inamullah Khan]

Dear every one,
I have a design of single deck floating roof based on example solved in bob long's book. The problem is that the clause H.4.1.2, of API 650 Appendix H says that roof be designed and build to rest in a horozontal plane, whereas as per the current avaible design calculations, deck plate is to be situated a certain calculated distance above the bottom edge of inner rim of pontoons. basically as per this clause roof shall be simple pan type with bulk heads(pontoon) on the top edge just like usual single deck floating roof but with bottom plate of pontoon and deck plates will be in the same horizontal plane. Can any one help me with what formulation to be used to check the integrity of this type of roof.

My question which roark formulation or any other you will use to calculate stresses in deck and pontoon. in type B case we take deck plate fixed at the edges and we have bob long example, but i have not seen any calculation for type A

regards,
Inam