The nozzle 1.5" LWNRF designed over head is failing without pad and as per latest amendment in code ASME SEC VIII Div.1 clause UG-36(c)(3)(a) the opening less than 60mm dia. in shell/head and shell thickness more than 10mm do not required to design.
Design DATA:
1. Design Pressure is 40.5 Kg/cm^2g/FV and Design Temp. is 260/205 Deg. C
2. Operating Pressure and Temp. is 35.95(Max) Kg/cm^2g and 205(max.) Deg. C
3. Reactor ID 2400mm, D'end type 2:1 Ellipsoidal, 44mm thickness min.
4. Nozzle size 1.5" ID Purge gas LWNRF, 15.87mm thick x 300#, with pad 140 x 28 mm thk, Centreline offset: 850.
5. MOC for D'end / Pad : SA516 Gr60(KCS), MOC for Nozzle: SA350 Gr. LF2
6. Design code: ASME Sec. VIII Div.1

The nozzle is constructed with pad and over client object to use of pad. Can anybody advise the action to take for this case.

Hi,

FROM THE TOOLS-->CONFIGURATION-->NOZZLE ANALYSIS DIRECTIVES-->UNCHECK "COMPUTE AND PRINT AREAS FOR SMALL NOZZLES". SO YOU FIND EXEMPTION FOR SMALL NOZZLES PER CODE.

If still not exempted then see following:
From the first instance based on Centreline offset: 850 mm as you specified, it looks that your chord length would definitely will be more than 60 mm. Hence your nozzle is not exempted per UG-36(c)(3)(a). You need to check reinforcement for the same.

Yes agreed that many client's object use of pad with forged nozzle. The best option for you is to design self reinforced hub type nozzle for your case.

Thanks.

Mukesh

Dear Mukesh,

Thanks for your reply. As per clause UG-36(c)(3)(a), small nozzle need not required to design, however the calculation results shown the failur of nozzle and accordingly for hydrogen service, we had applied reinforcement pad in LWNRF nozzle. Now client has objected to use of LWNRF nozzle with pad.

Please suggest, what solution have to adopt:
Option-1
1. Whether remove the pad from LWNRF nozzle with the exception from code.
2. Or same to retain as it is, since already constructed.
Option-2
1. Remove tha pad and reinforcement with welding.

Vikram,

I have checked yesterday your case with parameters specified from your end. It was exempted in my calculation. Yes one thing is there if you force software to calculate reinforcement even though it is exempted then for that case it will show you failure. I have suggested that u uncheck the option from the TOOLS-->CONFIGURATION-->NOZZLE ANALYSIS DIRECTIVES-->UNCHECK "COMPUTE AND PRINT AREAS FOR SMALL NOZZLES". SO YOU FIND EXEMPTION FOR SMALL NOZZLES PER CODE.

If you have done so and still it fails then I need to check your file.

Regarding solution to your problem:

Yes for hydrogen service, many client's don't want pad. If pad is already welded then you need to convince client. If he is not convinced then show Code exemption in calculation and prove that pad is not required and remove pad and do necessary action after if required per code.

Mukesh

Sorry to "hi-jack" the thread and go a little off topic, but since the point has been raised I was wondering:

1. What is the reasoning that companies/firms do not allow reinforcing pads with long weld neck flanges?

2. What is the reasoning that reinforcing pads for hydrogen service are not preferred?

Thanks in advance.