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API650 Tank annular bottom plate and bottom plate

API650 Tank annular bottom plate and bottom plate

Hi All,

If the tank bottom plate is 6mm and the annular bottom plate required also 6mm (as per table 5.1). In this case is it ok not to have the separate annular plate instead just extend the bottom plate to project 50mm outside the wall? which means wall just stit on the bottom plate.

much appreciated if some one clarify this.


RE: API650 Tank annular bottom plate and bottom plate

The main difference between a lap welded bottom plate and a butt welded annular plate is just that, the typical weld joint. If you choose to, it is permissible to omit the annular bottom plate by butt welding the entire bottom per API 650 5.5.5.

RE: API650 Tank annular bottom plate and bottom plate

If an annular plate is required, you can not use bottom plates even if the thickness is the same. They must be butt welded and annular in shape.

RE: API650 Tank annular bottom plate and bottom plate


How to check wheather annular plate is required or not?

RE: API650 Tank annular bottom plate and bottom plate

In API 650, annular plates are required in only two situations, described in sections 5.5.1 and M.4.1: the bottom ring of steel is designed using the allowable stress for materials in API Group IV or higher or if the tank is being built to Annex M and the diameter is 100 feet [30M] or more.

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