API 650 Annular Plate

[nabeel3]

Dear Experts ,

I am preparing for API Tank inspector exam . I could not understand the meaning of following . Can anyone help me to understand below
API 650, 13th edition Para 5.5.4 The ring of annular plates shall have a circular outside circumference, but may have a regular polygonal shape inside the tank shell, with the number of sides equal to the number of annular plates.

What is it means by number of sides equal to number of plates

Regards

 

[HTURKAK]

I think it is self explanatory..the inner circumference could be in a regular polygonal shape . That is, each annular plate exterior side will have curved circumference but interior could be straight . In this case , the interior polygon developing will have sides equal to no. of annular plates..

The following picture depicts the parts of bottom plates ..Notice that the annular plates interior circumference in a polygonal shape.
You can see the same picture and other info at ;

https://slideplayer.com/slide/1568223/

 

[nabeel3]

Mr. HTURKAK
In this case , the interior polygon developing will have sides equal to no. of annular plates..

In the pic shown above is it 20 sides and 20 annular plates.

Thanks

 

[HTURKAK]

True... if the no . of annular plates is 10, the interior polygon developing will be decagon..etc..

 

[IFRs]

The original question was "What is it means by number of sides equal to number of plates" and I think the above responses answer it. To repeat, the number of sides of the polygon made up from the inside edges of the annular ring must equal the number of annular plates. The sketch shown above has each annular plate being cut straight across. The language of the standard does not require this - the peaks of the polygon could be in the middle of each annular plate, not that I have seen this or would know why one would do this, but it would meet the standard.

 

[nabeel3]

Dear IRF
Sorry to ask you, what do you mean by
"Peaks of the polygon could be in the middle of each annular plate"
Regards

 

[IFRs]

This is what I meant - both have the same number of sides to the polygon...

 

[nabeel3]

Dear IFR,
Great. Thank you

 

[Bob Bilkhu]

Dear Readers,

I am involved in a project where we have replaced the tank bottom after which the contractor replaced the two shell cut out doors, we noticed that after a few days of settlement the floor and annulars in the location of the doors bulged up. Has anyone else ever experienced this or have any views as to what happened here.

 

[IFRs]

Bob -
This should be a new thread, you'll get better responses if you delete this post and make a new thread.

Regarding the picture, please help me understand what we are looking at. Is that a three-pass corner weld? Could you also explain what you are measuring in the picture? A ctross section sketch might also help...

 

[HTURKAK]

The measurement shows 75 mm bottom plate settlement near the shell. However the spirit level does not indicate that it is horizontal.. With the explanation and one picture , i will start the guessing;

- The new bottom placed on sand spacer material and the sand surface disturbed around door sheet ..
- The new bottom fillet welded the shell with a lot of passes..
- The new bottom does not extent to outside. The shell did not been slotted completely with a uniform cut made parallel to the tank bottom. In stead, the new bottom just welded to shell from interior...

If you want real helpful responds rather than guesses, pls provide more info. some pictures from outside etc. in a new thread as IFR suggested..

You may find some more info . with looking the previous threads ..This subject has been discussed in past with several threads.

 

[Dhurjati Sen]

This is not very unusual. Was the old bottom retained? In any case, follow API 653 reg. settlements.

DHURJATI SEN