Torispherical Head Calculation / Inside Crown radius value
Torispherical Head Calculation / Inside Crown radius value
(OP)
Hi ,
This is regarding the torispherical head thickness calculation , in UG-32(e) , it has been clearly mentioned that the inner crown radius (L) equals the outside diameter of the skirt (OD) , the same has been rightly mentioned in (CASTI Guidebook ASME Sec. VIII Div. 1 page.137 ) and (Pressure Vessel Handbook - E. Megyesy - 10th Ed) and many other sources..
But in ASME SEC.VIII-DIV.1Example Problem Manual PTB-4-13 page 29 ( example E4.3.4) , the inner crown radius L has been considered the same as the INSIDE DIAMETER of the vessel , the example is attached for reference
Now which case I`ve to considered during the solution if the given is the vessel inner diameter(Di) ? :
1- Considering L = Di + 2 vessel thickness ( which equals the skirt OD and conforms ASME in both UG-32 and appendix 1-4 ) (which equals in this case 72+2 *0.625 = 73.25 inch.
2- considering L = Di + head thickness + corrosion allowance = 72+ 0.625+0.125 = 72.75 inch.
None of these options is matching the solution shown in the example above , appreciate anyone who can clear this confusion.
Regards,
This is regarding the torispherical head thickness calculation , in UG-32(e) , it has been clearly mentioned that the inner crown radius (L) equals the outside diameter of the skirt (OD) , the same has been rightly mentioned in (CASTI Guidebook ASME Sec. VIII Div. 1 page.137 ) and (Pressure Vessel Handbook - E. Megyesy - 10th Ed) and many other sources..
But in ASME SEC.VIII-DIV.1Example Problem Manual PTB-4-13 page 29 ( example E4.3.4) , the inner crown radius L has been considered the same as the INSIDE DIAMETER of the vessel , the example is attached for reference
Now which case I`ve to considered during the solution if the given is the vessel inner diameter(Di) ? :
1- Considering L = Di + 2 vessel thickness ( which equals the skirt OD and conforms ASME in both UG-32 and appendix 1-4 ) (which equals in this case 72+2 *0.625 = 73.25 inch.
2- considering L = Di + head thickness + corrosion allowance = 72+ 0.625+0.125 = 72.75 inch.
None of these options is matching the solution shown in the example above , appreciate anyone who can clear this confusion.
Regards,





RE: Torispherical Head Calculation / Inside Crown radius value
RE: Torispherical Head Calculation / Inside Crown radius value
Thanks for replying , so you mean to say the following :
-The inside crown radius (L) as a value differs accordingly with the head wither it was standard or non-standard :
In other words if the torispherical head is standard , so the knuckle radius is 6% of the inside crown radius L , and L as a value shall equal the skirt OD , but if it is non-standard torispherical head , L in this case = K1D , where D here is the skirt ID as per appendix 1-4 symbols in ASME code , is it what you mean to say ? and this is fine , so who is deciding wither the head will be a standard or non-standard ?
I believe also all the dimensions here shall be considered corroded as per UG-16(e) of the code ,right ? i mean in case of non-standard head , D/2h values in table UG-37 from where you`ll get K1 and substitute in the equation shown above to obtain L should be in the corroded condition ( DIcorr = Di + C.A ( corrosion allowance)
Appreciate if you or anyone has a calculated example for both cases ( standard / non-standard torispherical head.
Regards.
RE: Torispherical Head Calculation / Inside Crown radius value
See Appendix 1.4(d) for general formula.
Regards
r6155
RE: Torispherical Head Calculation / Inside Crown radius value
so when you want to calculate the value of inside crown radius , you consider it = skirt OD or the same internal diameter of vessel (D)? , unfortunatly the answers still didn’t clear my point .
RE: Torispherical Head Calculation / Inside Crown radius value
Please, read slowly several times UG-32 and 1.4(d). Try to understand, it is very simple
Regards
r6155
RE: Torispherical Head Calculation / Inside Crown radius value
RE: Torispherical Head Calculation / Inside Crown radius value
This may be the reason that the code does not use the standard inside crown radius (ICR = OD) in the example.
If you use ICR = OD, then add corrosion allowance, then the inside crown radius in the corroded condition would equal ICR(corroded) = OD+CA > OD. This violates the code as is clarified in the interpretation.
So long story short, per the rules of ASME VIII-1, a standard torispherical head violates VIII-1 if your vessel has any corrosion allowance.
Cheers,
Marty
RE: Torispherical Head Calculation / Inside Crown radius value
Thanks for replying , focusing in the last sentence of your comment above which i found it logical and matching the requirments of UG-32 where the ICR should not exceed the outer diameter of the skirt,kindly refer the attachment i found in one of the PV references ( CASTI guide book ASME Sec VIII ) , where the example was for standard torispherical head with a corrosion allowance 0.125 inch and it clearly considered UG-32 not appendix 1-4.
for the attached example , if we adjust for corrosion allowance , we shall find the following :
L)corr = OD + C.A = (120+2x0.88)+0.125 = 121.9
OD (in corroded condition) = Di + 2C.A+ 2xThk = 120+ 2x0.125+2x0.88 = 122.01
from the results, Lcorr < OD)corroded condition , where UG-32 condition has been safely applied without any violation right ? correct me if something above was wrong please.
kindly note that the confusion am still falling in is facing sometimes references using L = ID while applying Appendix 1-4 Whereas some other references ( in the same attachment (CASTI guidebook)in the second case of non-standard torispherical head ) considering L = OD.
Thanks.