Weld to weld distance of Pressure part to Non Pressure part as per ASME Div 2

[prajwalchelsea]

Hi,

As per 4.2.5.6(e)1 of ASME Div 2 code, the distance between the saddle support and the Nozzle Opening (Gross structural discontinuity), the min weld edge to edge distance should be sqrt R*Ts (Mean vessel radius*Shell Nominal Thickness.
As this distance is very large for one of my equipment, is there any clause in Div 2 to exempt this requirement of min weld distance (i.e by doing PWHT or extra NDE)

Prajwal

 

[TGS4]

You could follow any of the other options available in 4.2.5.6(e). Or you could perform an evaluation per Part 5. Please explain what is the fillet weld and which is the gross structural discontinuity.

 

[prajwalchelsea]

@TGS4
It's the weld distance between saddle wear plate and nozzle opening weld, in this case the gross discontinty is nozzle opening.
As it is saddle wear plate any other option in 4.2.5.6(e)1 cannot be used.
Part 5 may be an option, but wanted to know any interpretation if it is available to exempt the requirement

 

[racookpe1978]

Please draw your desired configuration. It is not clear to me.

 

[prajwalchelsea]

@rocookpe1978

Find the attached drawing showing saddle wear plate to Nozzle BN weld distance.
Vessel ID = 3500
Shell Thk= 44 mm

Hence as per 4.2.5.6(e)1, the weld toe to toe distance should be sqrt R*Ts (Mean vessel radius*Shell Nominal Thickness
1.e sqrt (1722*44)=279.2mm
But the actual distance is 152mm as shown in the attachment.
wanted to know if I can exempt this clause by performing additional NDE or any other method in the code

 

[TGS4]

Part 5. Your only option.

 

[MrPDes]

In accordance with the clause, you could take your measurement from the OD of the nozzle neck (this is the edge of the gross structural discontinuity). This would get you from 152mm to about 200mm. Maybe this will make your job a little easier.

Even if your nozzle had a reinforcing pad, I think that the measurement could still be taken from the OD of the nozzle neck.

 

[TGS4]

This is not an NDE or quality issue. This is all about stress, the interaction of the discontinuity stress of the nozzle, the saddle, the presence of a fillet weld and (most importantly) the assumptions behind the Design By Rules formulae. Quite likely the configuration will be fine, but it needs to be demonstrated by a Part 5 evaluation.

Since this is a Div 2 vessel, how does the UDS address fatigue? Is the vessel exempt? If so, what method was used to exempt it?

 

[prajwalchelsea]

@TGS4

As per the Fatigue screening, the vessel is exempted from Fatigue and Fatigue analysis is not required for the vessel.

Issue is as the code does not give any exemption even if the vessel is not under Fatigue.

As the vessel is Heat Treated was thinking if there is any exemption clause for this

Looks like Part 5 is the only option now.

 

[prajwalchelsea]

@ MrPDes

Ya i can take distance from Nozzle ID to increase the distance, However the min distance required would still not be met.
It is not a reinforcement pad, it is a Lip type nozzle (Saddle type Nozzle)

 

[TGS4]

How is the vessel exempted from a fatigue analysis? Which method?

 

[prajwalchelsea]

@TGS4

Its as per Fatigue Screening procedure given in Div 2 using the Pressure Temperature loading chart provided by Client