Compression ring per API std 620

[alienitmeca]

Hello,

i am asking this questions for reference only:

when designing a compression ring, these factors must be calculated: Q (total circomferential force) and Ac (the net area to resist the compression fore):

QUESTION:

-in the case of finding Ac much bigger for than the participating area of roof and shell, which mean a big area to add in order to resist the compression force (say 50 square inche for example), what mesure should be taken ?

- in the case of having a positive compressive force Q, which mean the Q is acting as tensil force, should an area be added in order to resist against this force as well ?

looking forward to receiving your reply:

thank you in advance

 

[JStephen]

If Q comes out unreasonably large:
-Check that the application actually requires this design pressure and that the owner is prepared to pay the premium for it. Note that a flat-bottom tank may also require an unreasonably amount of anchorage in this case. It is not uncommon to see the pressure specified without a realization of the effects of it, and in many cases, the pressure can be reduced once the additional cost is pointed out.
-Increase roof slope
-Increase thickness of shell and roof members in the compression ring area so that additional area is reduced.

#2- Yes.

 

[alienitmeca]

JStephen,

thank you for the quick and precise answer !!

i can't find though a limitation in API 620 about the maximum allowable area to add, or is it a rule a the thumb ?

looking forwrd to receiving your replys.

thank you in advance

 

[JStephen]

There's not a set maximum amount of area that can be added. There are limitations on how wide the elements can be relative to their thickness, and limitations on how thick the plates are that can be welded under the standard.

 

[alienitmeca]

Jstephen,

could you be more specific about these limitaions, or where are exactly stated per API 620? i am asking about the the thickness not the widht because the widht is up a maximum of 16 * thickness of the plates.

thank yoy in advance.