Add studding pad

[Bobfromoh]

I have a 10' diameter CS API 650 tank, flat bottom.
It's about 15 years old. Customer wants to put a 6"
studding pad (thru a vertical weld)located about 6" from
the bottom plate. There is no information on this type
of connection. Does it still need a repad added? Can it just
be welded in or should it be made part of an assembly?
Thanks,

 

[JStephen]

Generally, on a 10' diameter API-650 tank, you don't need repads, as the "excess shell thickness" will furnish the reinforcing required. You can go through the reinforcing calculations and confirm.

 

[Bobfromoh]

Thanks for the reply. Api doesn't provide reinforcement calculations.
Api just states repads based on nozzle size. So are you suggesting to use
maybe the ASME pressure vessel code method?

 

[pdiculous963]

See paragraph 5.7.2. Reinforcement can be provided by any of the following:
1. A repad. (5.7.2.3(b)
2. Excess shell thickness above the required shell thickness. (5.7.2.3(d)
3. Excess nozzle thickness above what is required in Table 5-4(b). (5.7.2.3(c) and 5.7.2.4)

Limits of reinforcement are provided as well. The procedure is similar to the ASME pressure vessel code procedure, but may have some small tweaks. I haven't done these calculations for a few years though. I believe the reinforcement limits for the nozzle are different for one.

 

[Bobfromoh]

Thanks for the reply, You answered my question very well!

 

[MJCronin]

Can you share with us the reason that the client wants to add and expensive studding pad (or outlet) ?

These are more common on pressure vessels rather that API 650 style tanks.

MJCronin
Sr. Process Engineer

 

[Bobfromoh]

I don't know why a studding pad was used. I do know that the
customer said that space was very limited but it seems like
a regular nozzle would have work? If I get more info, I'll
let you know.

 

[JStephen]

API doesn't provide reinforccement calculations, YOU provide reinforcement calculations.