Torispherical (F&D) Head Design ASME VIII-1 UG-32(j) and 1-4(d)

[migraineboy]

Hi guys, need some advice.

I have this internal torispherical (F&D) head with the following dimensions;

1100 O.D
Crown Radius = 1100
Knuckle Radius = 110
Corrosion allowance = 1.5mm on both sides

i tried running in Compress but the program prompts this deficiency message,
" UG-32(j): The inside crown radius (1,101.5 mm) is greater than the head skirt outside diameter (1,097 mm). (Corroded)"

i checked that this deficiency is according to ASME interpretation VIII-1-86-175 in which the crown radius must not exceed
the outside diameter in corroded condition.

In this case, can i utilize mandatory appendix 1-4(d), retaining above dimensions, in design of torispherical head and still satisfy Code requirements?

Thank you

 

[fegenbush]

Have you tried applying the corrosion allowance to the exterior surface of the head? I don't have a copy of Compress here to see if that would work. Alternatively, you could decrease the crown radius by the corrosion allowance (1.5 mm). That would seem like the easy solution.

 

[c8829]

that deficiency message is just warning you can
1). either decrease crown radius
2). or in compress :codes/asme codes/options just uncheck the ASME interpretation VIII-1-86-175.

 

[migraineboy]

thanks for the reply...

@fegendush
the corrosion allowance is applied on both sides (1.5mm each on in/out). Crown radius is specified on client drawings so i intend to follow.

@c8829
yes, i already uncheck the intepretation. I checked compress support center and verified that supplementary formulas from mandatory appendix 1 can be applied to design of heads (i.e., 2:1, F&D...) in corroded condition.

 

[sharmass]

This warning is correct.
UG-32(j) requires that the crown radius cannot be more than the OD at skirt.
With corrosion allowance of 1.5mm, your crown radius will be 1101.5 that does not meet UG-32(j).

UG-32(j) requirements are mandatory and you should reduce Crown radius to 1098.5mm so that in the corroded condition also it satisfies the Code requirements.

Remember all Code calculations must be in corroded condition