Nozzle Re-Pad Questions for a vessel with 24" standard pipe

[791100]

I working on a storage vessel, it uses 24" pipe as the shell, heads are pipe caps. There are several nozzles with the size equal to or greater than 4". Two manhole's sizes are 10".
According to ASME code, the re-pads should be considered. The vender said it is not a standard vessel, and they are not going to stamp it per ASME Sec.VIII Div.1. I am struggling with the re-pads.
Could you give me some suggestions.

Thanks,

 

[TGS4]

I few questions to orient the problem:
1) Where in the world are you located (i.e. does your local jurisdiction require compliance with the ASME Code, by law)?
2) What is the length of the "storage vessel"?
3) Pressure/temperature/materials of construction?

 

[791100]

1) It is in CA, USA
2) Vessel Length is 10' TAN to TAN
3) DP: 15 PSI, DT: Ambient/ Material: SA-106B 3/8" THK, Horizontal vessel, Saddle and base plate: SA-36

Thanks,

 

[TGS4]

Because your vessel design pressure is 15 psi, per U-1(c)(2)(-h)(-1), your vessel may be exempt from begin required to comply with VIII-1. However, you may choose to do so, and have it designed, fabricated, inspected and tested in accordance with VIII-1, and to therefore have it stamped accordingly.

I take it that you have performed the opening reinforcement calculations according to UG-36 and UG-37? These calculations would be based on the nominal thickness of the vessel shell wall, as well as the required thickness from the calculations. For such a low pressure, the required thickness may be very low, and accordingly the openings may be self-reinforced. If they are not, then you can either chose a self-reinforcing nozzle, or a fillet-weld attached reinforcement pad on the shell.

Where's the confusion?

 

[791100]

Thank you very much for your comments.

Yes, the calculated required pad thickness is very low. What do you mean that the openings may be self-reinforced (don't need re-pad?), For example: The design THK is 3/8", the nominal THK:0.3125", and the calculated required pad thickness is 0.0625". So, in this case, it is self-reinforced and don't need additional re-pad. Is it what you mean.

Thank you again for your help.

 

[TGS4]

If you go through the calculations, you will find that the thickness required to resist the internal pressure may be very low - in your case on the order of 0.01in. So, for a pipe with nominal thickness of 0.3125in, you have 0.3025in of what essentially amounts to a repad. Go through the calcs yourself. You'll see.

 

[791100]

I calculated the minimum THK of the re-pad per UG-27(c)(1,2),yes, it is on the order of 0.01" which is very thin. The nominal shell THK is 0.3125", the calculated required min shell THK is 0.28". 0.3125"-0.28"=0.0325". And 0.0325">>0.01", so it can be self-reinforced, is it what you mean?

Thanks,

 

[TGS4]

The calculation of the shell thickness for pressure is per UG-27(c). That is the t_r used in the UG-37 calculations. Nominal thickness has nothing to do with it. I'm not sure where you get 0.28in.

Go through the UG-27 calc and the UG-37 in full.

 

[791100]

Yes, shell THK calculation is per UG 27 (C). The thickness 0.28" was obtained from external pressure 15 psig and ac 1/8" by Compress (87.5% after mill is counted). Actually, both internal and external pressures are ATM, we may don't need to consider external pressure. So the required min THK will be even lower. The re-pad calculation is per UG-37, it is low as well. So the nominal THK is much greater. It is greater than the sum of the require min shell THK and the calculated re-pad THK. So, it is self-reinforced, we don't need additional re-pad. Is it logically correct?

 

[TGS4]

Indeed

 

[791100]

TGS4, Thank you so much for your help.

 

[GenB]

About stamping, you are the customer.if you require stamping. It will be stamped. Its about price add.on. not impossible.