Insert pate at Nozzle opening.

[DK44]

Some times due to higher Nozzle loads, we have to use an insert plate at the nozzle which is a partial shell of higher thickness than the Shell.
1. Is such an insert plate at the nozzle opening allowed by ASME Sec VIII Div 1.
2. What are the dimensional limitations of the insert plate.

 

[SnTMan]

DK44, 1) I am not sure it is explicitly addressed as such, but see UW-16(c)(1), UG-42(d).

2) It must be at least as large as the limits of reinforcement. Limits may be restricted to match insrt plate size if reinforcement proves out. I would exclude any tapered portion (UW-9(c)) from those limits.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[JStephen]

I'm not aware of a requirement that it be as large as the limits of reinforcement (or as small)- certainly, that isn't true of repads. The reinforcing considered in design is limited by those limits, but not the physical plates.
Also note that per WRC 107, etc., it may be permissible to add repad thickness to shell thickness for design purposes, rather than using an insert.

 

[r6155]

For higher EXTERNAL LOADS the best practice is to increase shell thickness (with convenient length) instead of an insert plate.

Regards

 

[TGS4]

1. Is such an insert plate at the nozzle opening allowed by ASME Sec VIII Div 1.

Such an arrangement is permitted - or more specifically, it is not prohibitted. From my personal perspective, an insert plate is preferred to using a fillet-weld-attached reinforcement pad.

2. What are the dimensional limitations of the insert plate.

As stated above, the stated limits of reinforcement in UG-40 are where you can take credit for pressure-reinforcement. However, per the definition of D_p in UG-37, "actual size of reinforcing element may exceed the limits of reinforcement established in UG-40; however, credit cannot be taken for any material outside these limits". But this requirement is for pressure-only, and there is no stated limit for managing external loads.

 

[SnTMan]

I dis-remember and don't have the references, but it seems that the insert plate would have to be large enough that stresses at the junction of the insert and shell proper are within allowables.

For WRC-107 type calculations that would more-or-less correspond to checking stresses at a pad OD. I am sure there must be some attenuation length theorized within WRC-107. I assume FEA methods would reveal a proper limit for the insert size.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[DK44]

Thank you all for the good responses.
1. Further if any are welcome.
2. A partial shell (insert plate) is more economical than using higher thickness full shell band covering the nozzle RF limits.
But this is not shown in the code in picture form though the referenced code paras (thickened Shell plates) implied it.
Can any body tell their experience with such insert plate indicating the configuration.
3. In one of my jobs, the Shell thickness for Design pressure is 78 mm where as thickness of shell due to customer Nozzle loads comes to 156 mm. In such case an insert plate (partial higher thickness plate) is found economical. please give your views.

 

[r6155]

Did you think in forged nozzle? - see ASME VIII -I fig UW-16. 1 (f-1) to (f-4) and (g)
I assume that your nozzle must be with integral reinforcement.
Is your design for: cyclic, lethal, nuclear, low temperature, design temp >450ºC ?
My experience was with forged shell and forged nozzle (> 250 mm). Also with piping with integral nozzle in one forged piece.
I used Insert plate in several pressure vessels, it is a clean design. Avoid reinforcing pad.

"But this is not shown in the code in picture form though the.......". The code is not a handbook.

Regards

 

[SnTMan]

DK44, if more econimical, I see no reason not to.

Nozzle loads... Don't forget to check those flanges

The problem with sloppy work is that the supply FAR EXCEEDS the demand