API - 650 shell horizontal joint details 1

[massad]

I have a question regarding API - 650 shell horizontal joint details. Details shows that the bottom shell course is square bevel and the upper shell course is square , single or double V bevel. Why bottom shell course requires square bevel? Can we make it also single V or Double V.

Actually the tank fabricator already make V bevel on the bottom shell course horizontal joint. Now asking approval to proceed . I need some expert advise.

 

[IFRs]

Usually all top edges are flat and only the upper plate of the joint has a bevel because of gravity effects when welding.

 

[JStephen]

It may also be easier to bevel just one side of each plate instead of both sides. A detail that requires additional filler metal may have additional distortion when welded.
Regardless, API-650 doesn't limit the joint detail, and it would usually be varied for the most economical construction.

 

[chicopee]

JStephen, would you need a backing ring if you have a single V bevel in order to get full penetration?

 

[IFRs]

While API 650 does not specifically limit joint details, all the images in figure 5.2 happen to show the bottom plate flat.

 

[JStephen]

You wouldn't normally need or use a backing ring, just weld from both sides.
It occurs to me that the plates in question may have been installed upside down.
It could also be more awkward to work shims, etc., with that edge beveled.

 

[massad]

Thank you everyone for your input ....