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#68341 - 02/15/17 11:54 AM Flange Leakage/Stress Calculations Help
ZDawg Offline
Member

Registered: 12/02/14
Posts: 32
Loc: Metairie, LA
I'm currently trying to check a flanged connection to a pig trap but keep getting a failing result. I decided to check with no loads applied, just to see if my input was correct and I'm getting a failur with Longitudinal Hub and Maximum Average. I can't seem to find anything that will help me decipher the results here, but one item that threw up a huge red flag was the rigidity factor J. My results show J=670477. Considering J should be less than 1, I think something is hinky. Could someone please give this a look over and point me in the right direction? We don't have anyone else at the company who is very familiar with the flange analysis by Caesar.

FLANGE LEAKAGE/STRESS CALCULATIONS
Flange Inside Diameter [B] (User to verify) ......(in.) 23.000
Flange Thickness [t]..............................(in.) 4.000
Flange Rating (Optional) .............................. 600.000

Bolt Circle Diameter .............................(in.) 33.000
Number of Bolts ....................................... 24.000
Bolt Diameter ....................................(in.) 1.875
Bolt Initial Tightening Stress ............(lb./sq.in.) 30000.000


Uncompressed Gasket Thickness ....................(in.) 0.313
Grade of Attached B16_5 ANSI Flange.................... 1.100
Leak Pressure Ratio [m] ............................... 3.000
Effective Gasket Modulus ..................(lb./sq.in.) 437500.000

Externally Applied Moment ..... (optional) ....(in.lb.)
Externally Applied Force ...... (optional) .......(lb.)
Pressure [P]...............................(lb./sq.in.) 1440.000

Disable Stress Calculations (Y/N) ..................... N


Flange Type (1-8, see ?-Help or Alt-P to plot) ........ 1.000

Flange Outside Diameter [A].......................(in.) 37.000
Design Temperature ................................ F 120.000

Small End Hub Thickness [g0]......................(in.) 0.375
Large End Hub Thickness [g1]......................(in.) 2.500
Hub Length [h]....................................(in.) 4.000

Flange Allowable @Design Temperature ......(lb./sq.in.) 25700.000
Flange Allowable @Ambient Temperature .....(lb./sq.in.) 25700.000
Flange Modulus of Elasticity @Design ......(lb./sq.in.) 29.070
Flange Modulus of Elasticity @Ambient .....(lb./sq.in.) 29.500
Bolt Allowable @Design Temperature ......(lb./sq.in.) 25000.000
Bolt Allowable @Ambient Temperature .....(lb./sq.in.) 25000.000
Gasket Seating Stress [y] .................(lb./sq.in.) 10000.000

Flange Allowable Stress Multiplier .................... 1.000
Bolt Allowable Stress Multiplier (VIII Div 2 4-141) ... 2.000

Disable Leakage Calculations (Y/N) .................... N
Disable ANSI B16.5 Checks (Y/N) ....................... N
Flange Face OD or Lapjt Cnt OD....................(in.) 28.250
Flange Face ID or Lapjt Cnt ID....................(in.) 23.000
Gasket Outer Diameter ............................(in.) 28.250
Gasket Inner Diameter ............................(in.) 23.000
Nubbin Width .....................................(in.)
Facing Sketch ......................................... 1.000
Facing Column ......................................... 2.000


Flange Type: (Integral Weld Neck)

Effective gasket width parameters:
Effective gasket seating width, b......(in.) 0.5728
Diameter of gasket load reaction, G....(in.) 27.1044

SAFETY FACTOR SUMMARY for the different Flange Models
analyzed. (SAFETY FACTOR = Allowed/Actual)
SAFETY
FACTOR
Flexibility/Gasket Compression Model (Leakage).. 3.44
ANSI B16.5/Equivalent Pressure (Stress)......... 1.01
ASME Model Operating (Stress)................... 0.64
ASME Model Seating (Stress)..................... 0.73

FLANGE FLEXIBILITY MODEL ---------------------------------

BOLTED FLANGE CHARACTERISTICS:

Initial Tightening Stress in the Bolt (Not the seating
stress): 30000 lb./sq.in.

Approximate Torque required to induce the above initial
stress: 1620 ft.lb.


GASKET COMPRESSION: COMPRESSION
(in.)
After Initial Boltup (Ci)........... 0.0145565392

Loss-of due to Pressure (Cp)........ 0.0024395159
Loss-of due to Applied Moment (Cm).. 0.0000000000
Loss-of due to Applied Force (Cf)... 0.0000000000
Loss-of due to all loads (CL)....... 0.0024395159

Initial minus all Losses (Ci-CL).... 0.0121170236
For Leak-Proof Joint (Creq)......... 0.0061714286
Excess available (Ci-Creq) ......... 0.0083851106


LEAKAGE SAFETY FACTOR: (If less than one then joint
leakage is predicted.) (Allowed/Actual)

Pressure Only (Ci-Creq)/Cp ............. 3.44
Force Only (Ci-Creq)/Cf ................ 99999.00
Moment Only (Ci-Creq)/Cm ............... 99999.00

Pressure+Force+Moment (Ci-Creq)/CL ..... 3.44


EQUIVALENT PRESSURE MODEL ----------------------------

Equivalent Pressure (lb./sq.in.) ............ 1440.00
ANSI B16.5 Flange Allowable Pressure Rating . 1454.00

STRESS SAFETY FACTOR: (If less than one then joint
failure is predicted.) (Allowed/Actual)

ANSI B16.5/Equivalent Pressure ................. 1.01


ASME SECT VIII DIV 1 STRESS MODEL ------------------------

ACCORDING TO A05 APP 2-14, THE FOLLOWING RIGIDITY
FACTORS SHOULD BE LESS THAN 1.0

ASME Rigidity Factor "J", Operating Case .......670477.6250
ASME Rigidity Factor "J", Seating Case .........581779.8125

CALCULATED STRESSES (lb./sq.in.)

OPERATING ALLOW SEATING ALLOW
--------- ----- ------- -----

Longitudinal Hub .. 60086 38550 52908 38550 *
Radial Flange ..... 14836 25700 13063 25700
Tangential Flange . 17514 25700 15422 25700
Maximum Average ... 38800 25700 34165 25700 *
Bolting ........... 22647 50000 8821 25000

"*" Indicates Failure for an item.


STRESS SAFETY FACTOR: (If less than one then joint
failure is predicted.) (Allowed/Actual)

OPERATING SEATING
--------- -------

Longitudinal Hub .... 0.64 0.73
Radial Flange ....... 1.73 1.97
Tangential Flange ... 1.47 1.67
Maximum Average ..... 0.66 0.75
Bolting ............. 2.21 2.83

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#68347 - 02/15/17 10:12 PM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
Mandeep Singh Offline
Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
check your flange young's modulus, it should be about 29 * 10^6. You are off by a million there, I think.

Flange Modulus of Elasticity @Design ......(lb./sq.in.) 29.070
Flange Modulus of Elasticity @Ambient .....(lb./sq.in.) 29.500
_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#68357 - 02/16/17 11:15 AM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
ZDawg Offline
Member

Registered: 12/02/14
Posts: 32
Loc: Metairie, LA
Thank you. That was a silly mistake on my part. The flange is still failing with no loads applied. I cannot seem to find what is driving this Longitudinal Hub failure. Could you please provide anything explaining what drives these calculations or provide some possible insight into problem areas now. The results are still the same with the exception of the J factor.

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#68375 - 02/17/17 10:50 PM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
ANKIT_PATEL Offline
Member

Registered: 04/28/10
Posts: 71
Loc: GUJARAT, INDIA
It seems that design pressure is creating more problem than the loads in your case. Please check the flange rating and grade.

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#68397 - 02/20/17 03:09 PM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 6205
Loc: Houston, Texas, USA
Also remember that many standard flanges fail the ASME Sec VIII App 2 stress check. Standard flanges are "grandfathered" as acceptable.
_________________________
Regards,
Richard Ay - Consultant

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#68439 - 02/23/17 02:25 PM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
ZDawg Offline
Member

Registered: 12/02/14
Posts: 32
Loc: Metairie, LA
But if standard flanges are "Grandfathered" in, how would you go about checking if they will fail with added external loads due to thermal and pressure expansion?

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#68462 - 02/24/17 11:32 AM Re: Flange Leakage/Stress Calculations Help [Re: ZDawg]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 6205
Loc: Houston, Texas, USA
There is no prescribed method in the Code that explicitly tells us what to do. The advice is that it must be given consideration. There was a recently issued interpretation (BPV VIII-1-16-85) that stated this. That interpretation is paraphrased below.

Question: When superimposed static or dynamic reactions, as required by UG-22, are specified for the design of a pressure vessel, is it permitted to use an ASME standard product as defined in UG-11(c) produced in accordance with an ASME Standard referenced in UG-44 without performing supporting calculations that indicate the component is acceptable for all design conditions?

Reply: No
_________________________
Regards,
Richard Ay - Consultant

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