Nozzle on Storage Tank Roof Weld 1

[WarFT]

Hi all,

Is it a problem to add a nozzle or a square opening on the weld line of a storage tank roof? I cannot see anything on that in API 650.
Thnx

 

[IFRs]

The tank roof is not normally a pressure boundary - there no prohibition but it will kind of be a pain in the neck to do.

 

[WarFT]

Many Thanks IFRs
It is such a large opening that can't avoid the weld line so we will go ahead with it and pay attention to the weld. Structurally it does not require a reinf. doubling plate, as load is not much. But would you insert one to have cleaner weld at the nozzle neck?

 

[IFRs]

I'd use a repad. What size is it?

 

[valleytank]

Its not about having a cleaner weld. It's for distributing the load, especially if the roof is already thin.
It sounds like you are putting in a square hinged manyway on an existing roof? I would add the reinforcement especially crossing a seam.

 

[IFRs]

If it is a manway, API 650 says: "Roof manholes shall conform to Figure 5.16 and Table 5.13a and Table 5.13b. The effects of loads (other than normal personnel access) applied at the roof manhole and supporting roof structure shall be considered. Examples of such loads may include fall protection anchorage, hoisting, or personnel retrieval. The roof structure and plate around the manhole shall be reinforced as necessary."

This is reason enough to include a reinforcing plate.

 

[WarFT]

it is indeed a rectangular manway on a tank roof 6mm thk. what load would there be with a manway? the manway mass/weight itself is negligible. API is not clear about when to add reinforcing plates on tanks roof. Neither is the CODRES the french code for tanks. Valleytank, you mention load distribution, but the manway is a very light feature isn't it? although i'm adding a plate (just for the sake of...in case i've missed some understanding)i could have done without, could i? what do you guys generally do?

 

[IFRs]

per my previous post, "examples of such loads may include fall protection anchorage, hoisting, or personnel retrieval..."
I always include a re-pad and let the owner say "take it off" rather than not show it an not give them the opportunity to make that decision for themselves. Most if not all accept the drawings as is.