Ellipsoidal Head Thickness Calculation Inquiry
Ellipsoidal Head Thickness Calculation Inquiry
(OP)
Hi ,
This is regarding the design of ellipsoidal heads in pressure vessels, where I have a case here for a vessel of internal Dia = 2400 mm , and design pressure of P= 6barg, the design was done with the aid of PV-ELITE software.
while reviewing the final calculation report generated by one , i noticed in the elliptical head calculations part that the program directly considered Mandatory appendix-1 (SUPPLEMENTARY DESIGN FORMULAS) paragraph 1-4(c) instead of considering UG-32(d) , where the calculations have shown the factor "K " (a factor in the equations for ellipsoidal heads depending on the head proportion D/2h as per appendix 1-4 description ) , an snap shot of the report is shown below for reference :
"Elliptical Head From 30 To 40 SA-516 70 , UCS-66 Crv. B at 80 °C
Material UNS Number: K02700
Required Thickness due to Internal Pressure [tr]:
= (P*D*Kcor)/(2*S*E-0.2*P) Appendix 1-4(c)
= (6.059*2406.0000*0.997)/(2*137892.00*1.00-0.2*6.059)
= 5.2711 + 3.0000 = 8.2711 mm."
Any idea why the program considered appendix1-4(c) not UG-32 ? any clarification when we can use each ? as far as I know that we use this equation in case the elliptical head ratio is not 2:1 but this was not our case here as the vessel suppose to be ellipsoidal 2:1 head , was it something wrong during the input?
Appreciate your clarifications..
Regards,
This is regarding the design of ellipsoidal heads in pressure vessels, where I have a case here for a vessel of internal Dia = 2400 mm , and design pressure of P= 6barg, the design was done with the aid of PV-ELITE software.
while reviewing the final calculation report generated by one , i noticed in the elliptical head calculations part that the program directly considered Mandatory appendix-1 (SUPPLEMENTARY DESIGN FORMULAS) paragraph 1-4(c) instead of considering UG-32(d) , where the calculations have shown the factor "K " (a factor in the equations for ellipsoidal heads depending on the head proportion D/2h as per appendix 1-4 description ) , an snap shot of the report is shown below for reference :
"Elliptical Head From 30 To 40 SA-516 70 , UCS-66 Crv. B at 80 °C
Material UNS Number: K02700
Required Thickness due to Internal Pressure [tr]:
= (P*D*Kcor)/(2*S*E-0.2*P) Appendix 1-4(c)
= (6.059*2406.0000*0.997)/(2*137892.00*1.00-0.2*6.059)
= 5.2711 + 3.0000 = 8.2711 mm."
Any idea why the program considered appendix1-4(c) not UG-32 ? any clarification when we can use each ? as far as I know that we use this equation in case the elliptical head ratio is not 2:1 but this was not our case here as the vessel suppose to be ellipsoidal 2:1 head , was it something wrong during the input?
Appreciate your clarifications..
Regards,





RE: Ellipsoidal Head Thickness Calculation Inquiry
With 3 mm corrosion D/2h= 1,995 and K= 0,997, hence app 1-4 (c) is used.
Regards
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
but i think D/2h = 2 Already in this case as D = 2406 and h = D /4 = 601.5 , 2h = 1203 unless i am missing something , therefore : D / 2h = 2 , how did you get it 1995 ?
Regards,
RE: Ellipsoidal Head Thickness Calculation Inquiry
In corroded condition (3 mm corrosion) the head has a diameter of 2406 ID and the height inside is 603.
D / 2h in the corroded condition is: 2406 / (2 * 603) = 2406 / 1206 = 1.995. Which is not 'precisely' 2:1
Use the formula given in Appendix 1-4(c) where K = 1/6*(2 + (D/2h)^2) = 1 / 6 * (2 + (2406 / (2 * 603)) ^ 2) = 0.997
Oddly enough, Table 1-4.1 states that "interpolation is unnecessary", but software typically use the formula exactly.
RE: Ellipsoidal Head Thickness Calculation Inquiry
D corroded = 2400 + 2*3 = 2406
h corroded = 600 +3 = 603
D / 2h = 2406 / 2*603 = 1,995
Kcorroded = 0,997
See sketch
Regards
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
@ tombarsh , r6155
so you have to calculate it always in the corroded condition to obtain the factor K ?
RE: Ellipsoidal Head Thickness Calculation Inquiry
sorry man , you attachment is not working , i tried to downloaded it but i failed ...
RE: Ellipsoidal Head Thickness Calculation Inquiry
Regards
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
I try again and upload the file
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
D / 2h = ratio of the major to the minor axis of ellipsoidal heads, which equals the inside diameter of
the skirt of the head divided by twice the inside height of the head, and is used in Table 1-4.1, hence corrosion shall be added to calculate factor K.
Regards
r6155
RE: Ellipsoidal Head Thickness Calculation Inquiry
thanks for the sketch , now it`s working ..
Regards,