Minimum Shell Course Width for API 650 Tank 2

[khunmyomin]

API-650, para. 5.6.1.2 said "Unless otherwise agreed to by the Purchaser, the shell plates shall have a minimum nominal width of 1800 mm (72 in)".
Does this requirement apply for all of the shell courses? (which is not practical) Or it apply only to 1st course welded to bottom plate ?
Our client is pointing out this requirement, which is not practical for us to follow because the total height of the Tank.
What will be the best solution to answer ?
Thanks

 

[IFRs]

Read exactly what it says. No more, no less. Shell plates shall be 72" tall (wide) unless the purchaser agrees to something less. What is the tank size?

 

[JStephen]

First option is to ask if they're okay with using a smaller width, and explain why it's desired.
In the US, plate is commonly available in 120", 96", 72", etc. and that availability is assumed to some extent in the standard. You can avoid using a narrow course at the top by using wider courses on the other rings.
Actual widths used are based on availability, cost, labor cost, etc.
I've seen some overseas jobs where the available plate was 1500mm, and you just design and detail accordingly.
The main issue to watch out for is if the bottom ring is too narrow, the manway repads will hit the first seam.

 

[khunmyomin]

Thanks IFRs & JStephen,
The Tank height is 4300 mm Dia x 5300 mm H.
I asked API for it (whether this requirement "minimum shell course shall be 1800 mm" should applicable for all shell courses or Only bottom shell course) but I got the reply that "API is not able to provide an answer to your inquiry because API does not provide consulting on specific engineering problems or on the general understanding of its standards".
Seem I have to seek for our Client's approval.

Thanks & Have a nice day.

 

[IFRs]

The minimum applies to all shell courses. You can make them smaller but the tank won't be built in accordance with API 650 unless you get Client approval. Note: if your tank were to be made from stainless steel, per Annex S, shell courses must be 1200 mm (48 inches) wide (high).

 

[khunmyomin]

Thanks IFRs.
The MOC is Carbon Steel.
We had the discussion today. Hope it will be approved.