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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 length.
See the following procedure to model the actual flange length:
Note: This procedure is modeling the connection point between 2 flanges ( vessel / equipment flange and mating flange.
A. Start by inserting an anchor to represent the equipment flange side of the flange pair, Insert> Anchor.
B. Insert a short run of pipe equal to the actual flange length, Insert> Run (ex. 3.5").
C. Insert another pipe run to the next node point in the model, Insert > Run (ex. 4 ft).
D. Insert a flange at Nozzle / Equipment interface, in this example that would be the same node point as the anchor. Move active node point to the anchor, once there use Insert> Flange command.
On the flange dialog, change Joint End Type = "User Defined", set "Joint SIF" = 1.0
E. Select short length of pipe representing the actual flange length, 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 point representing the flange connection to the pipe. Press Insert > Xtra Data> Joint Type user SIF. Select the correct type of end connection or enter a user SIF.
(From AutoPIPE V8i 9.5)
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