This is an optional input. It has been a common practice in the industry to use the ANSI B16.5 and API 605 temperature/pressure rating tables as a gauge for leakage. Because these rating tables are based on allowable stresses and are not intended for leakage prediction, the leakage predictions that resulted are a function of the allowable stress for the flange material, not the flexibility, or modulus of elasticity, of the flange. To give you a comparison to the old practice, the minimum and maximum rating table values from ANSI and API are stored and are used to print minimum and maximum leakage safety factors that are predicted from this method. An example of the output that you get upon entering the flange rating is shown below:
EQUIVALENT PRESSURE MODEL ————————-
Equivalent Pressure (lb./sq.in.) 1639.85
ANSI/API Min Equivalent Pressure Allowed 1080.00
ANSI/API Max Equivalent Pressure Allowed 1815.00
According to the older method, this shows that leakage occurred if a carbon steel flange is used, and leakage does not occur if an alloy flange is used. Both flanges have essentially the same flexibility tendency to leak.
The following input parameters are used only for the ASME Section VIII Division 1 stress calculations:
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Flange Type
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Flange Outside Diameter
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Design Temperature
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Small End Hub Thickness
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Large End Hub Thickness
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Hub Length
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Flange Allowables
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Bolt Allowables
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Gasket Seating Stress
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Optional Allowable Multipliers
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Flange Face & Gasket Dimensions
Specify the Flange Type on the Flange Tab tab. To acquire material allowables from the Section VIII, Division 1 material library, use the Flange Material list on the Material Data Tab tab.
An input listing for a typical flange analysis is shown below:
CA E S A R I I MISCELLANEOUS REPORT ECHO
Flange Inside Diameter [B](in.) 30.560
Flange Thickness [t](in.) 4.060
Flange Rating (Optional) 300.000
Bolt Circle Diameter (in.) 38.500
Number of Bolts 32.000
Bolt Diameter (in.) 1.500
Bolt Initial Tightening Stress(lb./sq.in.)
Effective Gasket Diameter [G] (in.) 33.888
Uncompressed Gasket Thickness (in.) 0.063
Basic Gasket Width [b0] (in.) 0.375
Leak Pressure Ratio [m] 2.750
Effective Gasket Modulus(b./sq.in.) 300,000.000
Externally Applied Moment (optional)(in.lb.) 24,000.000
Externally Applied Force (optional)(lb.) 1,000.000
Pressure [P](lb./sq.in.) 400.000
The following inputs are required only if you wish to perform stress calcs as per Sect VIII Div. 1
Flange Type (1-8, see ?-Help or Alt-P to plot) 1.000
Flange Outside Diameter [A](in.) 41.500
Design Temperature°F 650.000
Small End Hub Thickness [g0](in.) 1.690
Large End Hub Thickness [g1](in.) 3.440
Hub Length [h](in.) 6.620
Flange Allowable @Design Temperature(lb./sq.in.) 17,500.000
Flange Allowable @Ambient Temperature(lb./sq.in.) 17,500.000
Flange Modulus of Elasticity @Design(lb./sq.in.) 0.279E+08
Flange Modulus of Elasticity @Ambient(lb./sq.in.) 0.279E+08
Bolt Allowable @Design Temperature(lb./sq.in.) 25,000.000
Bolt Allowable @Ambient Temperature(lb./sq.in.) 25,000.000
Gasket Seating Stress [y](lb./sq.in.) 3,700.000
Flange Allowable Stress Multiplier 1.000
Bolt Allowable Stress Multiplier (VIII Div 2 4-1411.000
Disable Leakage Calculations (Y/N) N
Flange Face OD or Lapjt Cnt OD(in.) 34.500
Flange Face ID or Lapjt Cnt ID(in.) 33.000
Gasket Outer Diameter (in.) 36.000
Gasket Inner Diameter (in.) 33.000
Nubbin Width (in.)
Facing Sketch 1.000
Facing Column 2.000
Disable Leakage Calculations (Y/N) N