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How to model typical flanges using AutoPIPE?
In AutoPIPE, flanges are a 1 point element with no length> The program only considers the flange weight and weld connection for SIF calculations. Assuming flange stiffness is same as the pipe is technically incorrect because a flange is more rigid than pipe. However, it does NOT affect analysis results to any significant extent. You can choose to model a flange as a single point or take into consideration the actual flange hub length.
A. On a Pipe run insert a node point at the flange matting surface (ex. Insert> Run> 1 ft from A00, creating node A11)
B. Insert Flange using Insert> Flange command.
Flange Type = Weld neck
Pressure Rating = 300 lbs
Weight = 15 lbs
Joint End Type = Weld Neck
Use Weld Factor for Bolt/nut weight = enabled (enabling this option will automatically update Bolt / Nut Weight accordingly)
Insert Mating Flange = enabled
Press OK to closed dialog
C. Done.
A. Perform Procedure #1 above before continuing.
B. Change the Joint End type of both flanges from "Weldneck" to "User defined" and set Joint SIF = 1.0.
C. Insert the pipe run equal to the flange hub length ( ex. 3 1/8") before and after the matting surface node point (ex. A11)
E. Select both pipe runs representing the flange pair (ex. select range A12 tp A13)
Press Insert > Rigid options over Range (Include Weight = OFF, Include Thermal Expansion = OFF), and press OK button. Pipe will be colored purple
Note: With regards to Rigid properties, It is more of a design decision by the individual person if there would be expansion of the flange in the axial direction, then the Rigid Properties > Thermal Expansion should be turned ON.
F. Select the node points representing the flange connection to the pipe (ex. A12 & A13).
Press Insert > Xtra Data> Joint Type user SIF. Select the correct type of end connection (ex. Butt Weld).
Final Model.
Again, assuming flange stiffness is same as the pipe is technically incorrect because a flange is more rigid than pipe. However, it does NOT affect analysis results to any significant extent. You can choose to model a flange as a single point or take into consideration the actual flange hub length.
AutoPIPE can model a wide range of flange types by using a variation of the techniques mentioned above (i.e. Weldneck, Slip-on, Lap joint, Socket weld, Threaded, etc...).
Flanges Piping Components - Modeling Approaches, Tips, Techniques
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