shell vertical joints

[MazaTEK]

Hello, the project im involved in at the moment is the contsruction of 23m width and 13,5m height tank according to API 650, the matter is that the shell is pre-assempled in 2 equal pieces as rolls. the point is that i cannot have 2 vertical joints all the way down. i ve considered the 5t criterio between vertical joints in adjacent shell courses, but! is there any minimum values for the lenght of the plates that im going to install or it is just the 5t criterio?? and where can i see it in api650 11th edition

 

[Bonswa]

There are no length minimums specified. Of course, you would like to have as little welding as possible. In your case, you would probably go with 6 - 40ft long plates to make up your circumference. That will allow you to do minimal vertical welding on the tank.

As long as you keep that 5t minimum weld spacing on the two pieces, the rest should line up correctly. you would have to verify that before assembling.

for the plate width, keep in mind the following from API-650:
5.6.1.2 Unless otherwise agreed to by the Purchaser, the shell plates shall have a minimum nominal width of 1800 mm (72 in.). Plates that are to be butt-welded shall be properly squared.

 

[JStephen]

If the tank is already fabbed, I would consider treating it as an acceptable deviation from API-650 (would need to be approved by the owner or other interested parties).

I believe in the older API-650's, they actually allowed shell courses to have the vertical joints aligned.

 

[JoeTank]

JStephen,
The older API-650 had a 5t offset requirement, but excluded shell courses which were governed by minimum thickness criteria. The exemption was dropped in early 1990s, I believe.

Joe Tank