Torispherical Head Thickness Calculation problem, pls help me

[Sriram_be]

Vessel ID: 2100 mm
Length (T/T): 3900 mm
Thickness: 6 mm (considered)
Vessel Type: Horizontal Cylindrical with Torispherical Dish End
I manually calculate this
Inside Crown Radius of the Torispherical is ( L ): 2112 (OD of the Vessel) &
Inside Knuckle Radius is ( r ) 126.72 (6% of Inside Crown Radius),
As per ASME Sec VIII Div – 1 UG 32 (e)
The condition ts/L ≥ 0.002 is satisfied
And the formula for the thickness calculation is tp = 0.885 P L / S E − 0.1P
-------------------------------------------
But as per ASME Sec VIII Div – 1 Appendix – (1- 4)
The same condition is ts/L ≥ 0.002
The L/r ratio is involves ……….
L /r ratio is inside crown radius to the inside knuckle radius, used in Table 1-4.2
Thickness formula is
t p = P L M / 2 S E − 0.2 P
and L/r = above 16 means M factor calculate separately…..for another formula in App 1-4
-------------------------------------------
In my case the L/r is 16.6 and I have to calculate the M factor value separately.
-----------------------------------------------------------------
Here my questions are,
1. Is it wrong using thicknesses formula tp = 0.885 P L / S E − 0.1P.
in this condition (L/r is 16.6) as per ASME sec VIII div -1 UG -32 (e) .Why because I already consider the inside knuckle radius is 6% inside crown radius as per the code.
2. As per UG -32(e) and App 1-4, when I go for these L/r ratio?
Please help me in this query and am expecting your comments with references please …..

[cpchonburi]

Please find below Interpretation. May be help.

[rcmathews]

In short:
1. UG-32 formula applies to torispherical heads that are in a specific subset that the inside crown radius = the outside diameter of the skirt and the inside knuckle radius is 6% of the inside crown radius. Please note that the paragraph states ICR is EQUAL to OD and the IKR IS 6% of ICR. If your head is a true ASME F&D and meets these criteria, then use this formula.
2. Appendix 1-4 exists to deal with torispherical heads that have differing geometries, for example an 80/10 head, which has a crown that is 80% of the skirt OD and a knuckle that is 10% of the skirt OD. One would use an 80/10 head because it requires only about 2/3 the thickness that a true F&D head requires.
3. I always use App 1-4 first, then run UG-32e. Sometimes 1-4 is more liberal with the required thickness. Please examine factor M formula in App 1-4d and Table 1-4.2 of M values. Please contact me if you require additional help.

[Sriram_be]

Thank You all for your valuable contribution.

Regards,

Sriram

[rcmathews]

I failed to mention this in my post:
Per UG-32j:
The inside crown radius cannot exceed the outside diameter of the skirt.
The inside knuckle radius cannot be less than 6% of the inside crown radius.
Please review Table 1-4.2 of App 1. You will notice the max L/r ratio is 16 & 2/3, which is 6%.

To the other respondent, thanks for the attached interpretations.

[cpchonburi]

FYI-all dimension shall be in the corroded condition, if any.

[duazo2009]

Vessel ID: 2100 mm
Length (T/T): 3900 mm
Thickness: 6 mm (considered)
Vessel Type: Horizontal Cylindrical with Torispherical Dish End
I manually calculate this
Inside Crown Radius of the Torispherical is ( L ): 2112 (OD of the Vessel) &
Inside Knuckle Radius is ( r ) 126.72 (6% of Inside Crown Radius),
As per ASME Sec VIII Div – 1 UG 32 (e)
The condition ts/L ≥ 0.002 is satisfied
And the formula for the thickness calculation is tp = 0.885 P L / S E − 0.1P
-------------------------------------------
But as per ASME Sec VIII Div – 1 Appendix – (1- 4)
The same condition is ts/L ≥ 0.002
The L/r ratio is involves ……….
L /r ratio is inside crown radius to the inside knuckle radius, used in Table 1-4.2
Thickness formula is
t p = P L M / 2 S E − 0.2 P
and L/r = above 16 means M factor calculate separately…..for another formula in App 1-4
-------------------------------------------
In my case the L/r is 16.6 and I have to calculate the M factor value separately.
-----------------------------------------------------------------
Here my questions are,
1. Is it wrong using thicknesses formula tp = 0.885 P L / S E − 0.1P.
in this condition (L/r is 16.6) as per ASME sec VIII div -1 UG -32 (e) .Why because I already consider the inside knuckle radius is 6% inside crown radius as per the code.
2. As per UG -32(e) and App 1-4, when I go for these L/r ratio?
Please help me in this query and am expecting your comments with references please …..

hi!

Please find attached sample design calculation with torispherical head;

Internal Pressure Calculation Results :

ASME Code, Section VIII, Division 1, 2007 A-09

Torispherical Head From 10 To 20 SA-516 70 , UCS-66 Crv. B at 80 C

Inside Corroded Head Depth [h]:
= L - sqrt( ( L - Di / 2) * ( L + Di / 2 - 2 * r ) )
= 1515.00-sqrt((1515.00-2106.00/2)*(1515.00+2106.00/2-2*93.72))
= 466.278 mm.

M factor for Torispherical Heads ( Corroded ):
= (3+sqrt((L+C)/(r+C)))/4 per Appendix 1-4 (b & d)
= (3+sqrt((1512.000 + 3.0000 )/(90.720 + 3.0000 )))/4
= 1.7551


Note: r is less than 6% of the head skirt OD.
Please check UG-32(j) and UG-81 for Code compliance.

Required Thickness due to Internal Pressure [tr]:
= (P*L*M)/(2*S*E-0.2*P) per Appendix 1-4 (d)
= (350.000*1514.9999*1.7551)/(2*137.90*1.00-0.2*350.000)
= 3.3755 + 3.0000 = 6.3755 mm.

Max. Allowable Working Pressure at given Thickness, corroded [MAWP]:
= (2*S*E*t)/(M*L+0.2*t) per Appendix 1-4 (d)
= (2*137.90*1.00*5.0000)/(1.7551*1514.9999+0.2*5.0000)
= 518.381 KPa.

M factor for Torispherical Heads ( New & Cold ):
= (3+sqrt(L/r))/4 per Appendix 1-4 (b & d)
= (3+sqrt(1512.000/90.720))/4
= 1.7706

Maximum Allowable Pressure, New and Cold [MAPNC]:
= (2*S*E*t)/(M*L+0.2*t) per Appendix 1-4 (d)
= (2*137.90*1.00*8.0000)/(1.7706*1511.9999+0.2*8.0000)
= 823.611 KPa.

Actual stress at given pressure and thickness, corroded [Sact]:
= (P*(M*L+0.2*t))/(2*E*t)
= (350.000*(1.7551*1514.9999+0.2*5.0000))/(2*1.00*5.0000)
= 93.107 N./mm²

Straight Flange Required Thickness:
= (P*R)/(S*E-0.6*P) + c per UG-27 (c)(1)
= (350.000*1053.0000)/(137.90*1.00-0.6*350.000)+3.000
= 5.677 mm.

Straight Flange Maximum Allowable Working Pressure:
= (S*E*t)/(R+0.6*t) per UG-27 (c)(1)
= (137.90 * 1.00 * 5.0000 ) / (1053.0000 + 0.6 * 5.0000 )
= 652.898 KPa.

Percent Elong. per UCS-79, VIII-1-01-57 (75*tnom/Rf)*(1-Rf/Ro) 6.334 %
Note: Please Check Requirements of UCS-79 as Elongation is > 5%.

MDMT Calculations in the Knuckle Portion:

Govrn. thk, tg = 8.000 , tr = 5.000 , c = 3.0000 mm. , E* = 1.00
Stress Ratio = tr * (E*) / (tg - c) = 1.000 , Temp. Reduction = 0 C

Min Metal Temp. w/o impact per UCS-66 -29 C

MDMT Calculations in the Head Straight Flange:

Govrn. thk, tg = 8.000 , tr = 3.968 , c = 3.0000 mm. , E* = 1.00
Stress Ratio = tr * (E*) / (tg - c) = 0.794 , Temp. Reduction = 11 C

Min Metal Temp. w/o impact per UCS-66 -29 C
Min Metal Temp. at Required thickness (UCS 66.1) -40 C

Elements Suitable for Internal Pressure.

PVElite is a registered trademark of COADE, Inc. [2010]

I hope this is helpful for you.

Cheers,
duazo2009