Nozzle Extension Inwards

[Nickmack]

I am looking to add a diffuser to an existing flush type 10" receival nozzle. Is it ok to just go ahead and weld that diffuser pipe onto the internal portion of that flush type nozzle of the storage tank?
Stored product: Crude
Tank Type: External Floater ( 174' Dia, 48' Height)

 

[JStephen]

I don't recall what the API-653 requirements are for that, if it is addressed.

However, I would point out that larger tanks commonly have nozzles inserted into shell plates and stress-relieved prior to assembly, in which case, it'd be undesirable to weld it that way.

 

[IFRs]

I'd be tempted to leave the hole and nozzle neck alone and attach the larger pipe without a reducer to the tank shell using clips so it is removable or welding the pipe to the shell. The hole in the shell is where stresses are, it should be a full-penetration weld and have adequate reinforcement. The diffuser typically has little force on it. Examine the tank shell for laminations, etc before welding to it. Establish it's grade and stop if it is API group IV or above.

 

[Nickmack]

IFRs the shell course is 1" thick what implication/s will i have just welding to the shell? Do i need to conduct heat treatment if i weld the 20" directly to the tank?

 

[JStephen]

Check the shell material if possible, and refer to 5.7.4.2 and 5.7.4.3 in API-650.

If the shell is A36, and shell plate is 1" or less, no problem.

If the shell is A36 and over 1", or if it's A516-70, A573-70, etc., then see 5.7.4.3. In that case, see 5.5.4.2(a) in API-650, which specifies spacing to the non-stress-relieved weld. And see 9.8.3 in API-653.

 

[IFRs]

I'd check for internal laminations in the area to be welded and follow JStephen's advice.