API 650 -SECTION 5—DESIGN 4

[Abeerj]

Dear sirs,
I don't understand the following paragraph from API 650 - section 5-Design - 5.1.5.2 Vertical Shell Joints:
b. Vertical joints in adjacent shell courses shall not be aligned, but shall be offset from each other a minimum distance of 5t,
where t is the plate thickness of the thicker course at the point of offset.

Can you help me to understand this issue..
Thanks in advance.

 

[Syahar1975]

The way I read this paragraph 5.1.5.2:

Vertical joints on shell course no 2 shall not be exactly above vertical joint shell course 1.

The distance of Vertical joint on shell course no 2 shall be minimum 5T from vertical joint shell course 1.

T is the plate thickness of thicker plate.

Typical for vertical joins on shell course 3 and vertical joint shell course 2 and next verticals on the next shell course.

Usually tank designer use 1/3 length of the plate as offset from vertical shell course 2 to vertical course #1.

 

[Abeerj]

Thanks Syahar1975 for your prompt reply.
I still didn't get it ,do you have any photo can explain more ???

 

[bimr]

It is specifying that the tank seams don't line up so that the tank is stronger:

Compare the seams to that of a bolted tank:

 

[Syahar1975]

Abeerj,

Please find the attach sketch for your info.

 

[Abeerj]

Thanks a lot Syahar1975 , bimr ....You helped me very mucu

 

[syed051]

@Syahar1975,@bimr, @Abeerj: Where are you guys are working(country) and whats your positions?

 

[valleytank]

Even though 5t spacing is the bare minimum I suggest you increase this distance to space out your areas of residual stress in closely concentrated seam intersections.

 

[Duwe6]

concur with valleytank; space them out about 1m / 3ft, if not more.

 

[Syahar1975]

Usually the tank designer will show in the drawing (shell development or nozzle orientation drawing) the distance between to adjacent vertical.

In my experiences mostly 1/3 of plate length.I have seen 500 mm in one of my project.

@Syed051,

My email : Syahar1975@yahoo.com