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.
Again, the flange component is only a single node point where the SIF value & weight are calculated and inserted. Therefore where ever the flange is inserted will be the location of SIF and weight. The user as a choice of where to insert the flange:
Option 1. Insert Flange at Weld location, correctly identify the SIF and weight.
Option 2. Insert Flange at the face connection, set dialog settings as needed, note the Joint SIF value automatically calculated. Now change the Joint End type = User, and enter 1.0. Select the node point where the flange is welded to the pipe, insert User SIF = recall automatic value calculated in previous step.
This procedure will use Option 2.
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)
D. Select both pipe runs representing the flange pair (ex. select range A12 tp A13)
Press Rigid Options Over Range (Insert > Properties > Rigid Options Over Range) command, When the dialog appears, the user has to decide if the given options are enabled or disabled.
Include weight
Option 1. Enabled - If enabled the weight of piping (pipe + insulation + Cladding + Lining + Contents) are added in the analysis. Depending on your Flange settings, the flange weight may be in addition to this weight. Reopen the flange component and adjust the weight accordingly to correctly calculate the total weight during the analysis.
Option 2. Disabled - If disabled the weight of piping (pipe + insulation + Cladding + Lining + Contents) are removed from the analysis. Depending on your Flange settings, the flange weight may correctly account for the weight of pipe + insulation + Cladding + Lining + Contents over the hub length. Reopen the flange component and adjust the weight accordingly to correctly calculate the total weight during the analysis.
Include thermal expansion
It is more of a design decision by the individual person if there would be expansion of the flange in the axial direction
Option 1. Enabled - thermal expansion per the temperature load case settings will be accounted over the assigned length of rigid properties during analysis.
Option 2. Disabled - all thermal expansion will not be accounted for the assigned length of rigid properties.
Note, consider adding a new PIPEID to represent the Flange hub length. One could set the Material Properties = NS, adjust the values as needed, However make Density = 0.00. Doing so would make it easier when modeling flanges because only the pipe weight would be ignored while the other pipe weight due to insulation + Cladding + Lining + Contents will be correctly calculated. The only drawback being that all the automatic values generated on the Press/Temp/Pipe ID tab will at this time will revert to values that would need to be manually updated as the temperature changed per load case from this point forward.
E. Select the node points representing the flange connection to the pipe (ex. A12 & A13).
F. 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
Bentley AutoPIPE