API 653 Hop Tap for 8" nozzle

[jfacevedob]

Dear Sir.

Does anyone coult tell me if, for a tank of dia x H = 27.625' (liquid hight 20.8'), we can performance a hop tap of 8" nozzle having a shell average meassured thickness of 0.208". I know that API 653 require a minimum thickness of 1/4" but the shell plate required by calculation, using A283C plates and E = 0.7, is 0.1472".

In case that we can not performance the hot tap procedure I would apprciate any alternative to place in the tank a 8" nozzles without empty the thank

Thank for your help

 

[IFRs]

As you note, API 653 calls for a minimum shell thickness greater than yours.
Possible options:
Don't comply with API 653
Hot tap two 6" nozzles and pipe them together
Hot tap a shell manway cover plate with an 8" nozzle, if the cover plate is 1/4" or more

 

[MJCronin]

Sometimes you must empty the tank ....

No spare empty tank available ? ...... Discuss this with the plant manager and the process engineer, perhaps this could be a future enhancement.

Suggest that you consider the modified shell manway cover plate fix. You can have a replacement made in the shop and ready to swap out during a brief shutdown

MJCronin
Sr. Process Engineer

 

[mk3223]

Is the required minimum thickness the concern of the burn through during the hot tap?
Check with your plant Material Engineer to see if it helps to add a butter weld layer on the pipe for the hot tap connection.