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Add studding pad

Add studding pad

Add studding pad

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?

RE: Add studding pad

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.

RE: Add studding pad

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?

RE: Add studding pad

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

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.

RE: Add studding pad

Thanks for the reply, You answered my question [u]very[/u] well!

RE: Add studding pad

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.

Sr. Process Engineer

RE: Add studding pad

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.

RE: Add studding pad

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

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