UG-45 Minimum thickness in WNRF Flange

[Morcuse]

Hello,

I'm currently evaluating the nozzle neck minimum thickness required by the ASME Section VIII Div. 1 code.

We are intending to weld directly a welding neck raised face flange directly to the vessel. The pipe thickness specified for the pipeline is 0.28 in, having considered already 3 mm of CA for the vessel.

The nozzle minimum thickness (ta) per UG-27 is 0.19351 in, considering 3 mm of CA.

tb1 is 0.5831 in for the shell, cosidering 3 mm of CA.

tb3 per Table UG-45 for NPS 6 is 0.245 in + CA, which results to be 0.36311 in(having considered 3 mm CA per UG-45 requirements).

I understand that Table UG-45 considers 12.5% of mill tolerance for pipes. I wonder if this would be a correct evaluation of the flange's welding neck.

In compliance with tb3, the minimum nozzle neck thickness in this case needs to be 0.36311 in, which impacts the inside diameter for the pipeline.

I'm guessing to respect UG-45 I would need to increase the pipeline schedule to 80, which results in a standard pipe thickness of 0.432 inches, and consecuently the WNRF flange minimum thickness would be increased as well to 0.432.

This is my first nozzle neck evaluation. I apologize for any mistake beforehand. This forum has already been an amazing help for my work.

Thank you.

Roberto

 

[racookpe1978]

Draw a sketch of your installation: Are you going to remove the "pipe" section of the RFWN, and weld the resulting flange to the PV? Or just weld the Pipe to the PV with the usual fillet weld?

 

[SnTMan]

Bore of vessel connection and attached piping are not required to match, they are mismatched all the time.

Regards,

Mike

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

 

[Morcuse]

Thank you both for your help!

Regarding racook, we are intending to weld the welding neck end directly to the vessel with the usual fillet weld. This needs to be a 600# WNRF SCH 80 Flange, per UG-45.

I believe if the bore of the vessel connection and attached piping are not required to match, the flange attached to the pipeline can be of std schedule (SCH 40) per ASME B31.3, since it is no longer considered a "nozzle", out of the Section VIII Div. 1 domain. This would result in an difference of bore dimensions for the NPS 6" nozzle.

The thing is, having done the same analysis for a NPS 2" nozzle on the same vessel. It would require a 0.253 in minimum thickness per UG-45 considering the same 3 mm CA. Again, I would have the same case: Two 600# flanges, the one connected to the vessel directly with SCH 160, and the other one connected to the pipeline with SCH 80.

I believe both of these cases are acceptable? Even though they impact on the fluid pressure/velocity, caused by the sudden expansion through the flanges with different inside diameter.

Edit: Pipedata pro says that a 600# WNRF Flange SCH 160 isn't even normally manufactured. I believe switching to a Long welding neck raised face flange would be better for this particular application?

 

[SnTMan]

Well, if you go LWN, you'll really have an ID mismatch.

Regards,

Mike

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

 

[jte]

Some advantages of LWN, in particular with small bore nozzles, is that they are very robust and inherently provide a bit of a nozzle neck / standoff. With a small bore WN flange welded directly to a vessel, I would wonder how much clearance is left for tools to access the nuts? Sounds to me like a fine idea in an engineering (management) office, not such a good idea when the steel hits the field. Has this proposal been approved by the field foreman or superintendent?

The other thing which strikes me in the original post is the mention of a "the usual fillet weld". For service which requires CL-600 flanges, I'd think that full penetration welds would be a no-brainer for the engineer.

 

[GenB]

Your AI statement is correct. It reads and locks the vessel to the mdmt designed and operated for.