Bottom sketch plate width per API-650 Paragraph 5.4

[MikeG7]

Hi All,

Paragraph 5.4 from API-650 says that the minimum width of sketch plates should not be less than 1800 mm unless purchaser agrees.

For my particular application, I am using 2m wide plates, 6m long. The tank is 7m inside diameter. For the center plate on the bottom I use the full 6m long plate (2 m wide) to avoid cutting. That leaves the adjacent plates 2 m x 0.55m on each side as per attached picture.

The plate at 0.55m x 2 m wide - is this in violation to API-650 which requires plates to be 1800 mm minimum "width"?

I tried searching for "sketch" & "plates" and as you can imagine a lot (literally a couple of hundred) results came up, hence my advance apology if there is an applicable post dealing with such.

Michael

 

[JStephen]

I would say that is okay, provided the 3-way joints maintain the required minimum distance from the shell.

 

[Geoff13]

In your sketch, the plate you are concerned with is still 2 m wide, and thus in conformance with API 650.

As this plate narrows towards it's ends, the resulting 3 way lap must be at least 300 mm (radially) from the shell per clause 5.1.5.4.2, which may limit this layout.

 

[MikeG7]

Thank you both for your insight.
Would anyone be kind enough to provide an actual photograph of a 3-lap joint (the image from the Code is rather baffling my brain!)

 

[Geoff13]

It could look like this:
3 way lap picture

 

[MikeG7]

Thanks Geoff! What I needed exactly

 

[HTURKAK]

Hi MikeG7 (Mechanical)(OP),

The sketch that you have posted which is showing the sketch plates does not violate the API 650 provided that the thk. at least 6 mm.

How ever , IMO, needs improvement to reduce the amount of welding and waste plate.


You may research with ( storage tank bottom plates ).. Literally possible outcomes will be,