API 620 Annular plate

[BZ29]

I have gone through API620 in detail and found no requirement for RT of annular plate, annular plate thickness & width calculation unlike API650. I am just curious about the possible reasons, as API620 tanks seems to be more complex.

 

[Dhurjati Sen]

API 650 is specifically for oil storage, hence extra precautions.
Sizes and loadings are almost same in both the standards.

DHURJATI SEN
Kolkata, India

 

[BZ29]

What if API620 tanks are also being used in oil refinery? Similarly, there is no testing mentioned for shell to bottom fillet weld, unlike API650 which requires penetrating oil test for this joint.

 

[JStephen]

Part of the reason may be that API-650 tanks normally have an annular plate either due to large diameter or due to seismic uplift.
Whereas API-620 flat-bottom tanks are usually anchored, so less need for the annular ring.
Note that in API-650, if you use an annular ring "just because" and not due to being required by the standard, much of the inspection goes away as well.
I don't recall the testing criteria in 620, but the overall tank is leak-tested, so the corner weld would be tested along with that.

 

[HTURKAK]

Please look Appendix P NDE and Testing Requirements Summary.

Pls provide more info. for the subject tank. ( Appendix Q ,R spherical etc. ) sizes , pressure , content etc. to get better responds.

The scope of API 620 covers
That is , if you cut a section parallel to ground you shall get a circle .This can be Cylindrical side wall flat-bottom tanks ( one curvature ), spherical ( having two curvature ) .

For instance if you need annular plate for seismic resistance , the same criteria as defined in API 650 .



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