Calculate pressure stiffening using TBK 5-6
Pressure stiffening of bends is required for flexibility factors only and is done by default. You can disable pressure stiffening by excluding the Use Pressure Stiffening option in the setup file. You can enable pressure stiffening for stress intensification factors (SIF)s as well by including the Use Pressure Stiffening option.
Expansion stress in TBK 5-6
Summing the longitudinal component F/A into the stress calculation is not defined by default in the code. You can enable the axial force term in the code stress by including the Add F/A In Stress option in the configuration file.
The code uses a circumferential weld strength factor (Z) when calculating longitudinal
pressure stress. Enter this value as Eff.
Calculate cyclic reduction factor using TBK 5-6
You can calculate the cyclic reduction factor using the following equation: F = (7000/Ne)0.2
Where
Ne = Number of Anticipated Cycles
F may be as high as 2.34 but not greater than 1.0 when Rm governs the expansion stress
allowable.
Calculate SIFs for bends and intersections using TBK 5-6
In-plane and out-of-plane SIFs for bends and intersections use the same stress equation.
Calculate the Norwegian allowable stress limits
Use the equations below to calculate the stress allowables.
Expansion Allowable = Sr + F2 - SSUS
Sustained Allowable = F2
Occasional Allowable = Occ * F2
Where:
|
Sr = |
Minimum of 1.25F1 + 0.25F2; Fr * Rs - F2; or Fr (1.25 R1 + 0.25 R2) The latter for higher temperatures; above 425°C for austenitic stainless steel, or above 370°C for other materials. |
|
F2 = |
Hot Allowable Stress (entered in Sh) |
|
OCC |
Occasional Load Factor from the configuration file (defaults to 1.2) |
|
SSUS = |
Sustained Stress |
|
F1 = |
Allowable Stress at Ambient (entered in Sc) |
|
Fr = |
Cyclic Reduction Factor |
|
RS = |
Permissible Extent of Stress for 7000 Cycles (from Code Table 10.2) |
|
R1 = |
Lesser of F1 and 0.267 RM |
|
R2 = |
Lesser of F2 and 0.367 RM |
|
Rm = |
Ultimate Tensile Strength at room temperature |
Calculate SIFs using TBK 5-6
SIFs for fitting types 6 (branch with raised edge radius), 7 (branch on locally thickened pipe), 13 (conical reducer with knuckles), and 14 (reducer without knuckles) have not been implemented in CAESAR II so you must enter them manually. The Norwegian code offers an alternative stress analysis method in Appendix D. However, CAESAR II does not implement this method.
TBK 5-6 reducer default values
Calculate the SIFs by using the following equation: 2.0 max or 0.5 + .01*alpha* SQRT(D2/t2).
Where:
D2 - Diameter of the Small End
t2 - Thickness of the Small End
alpha - the slope of the reducer
TBK 5-6 flexibility factor default value
The default flexibility factor value is 1.0.