Please see the following AutoPIPE help section: Help > Contents> Contents Tab> Modeling Approaches> Modeling Approaches> Bend> Reducing Elbow
From online help:
ModelingAutoPIPE does not have a reducing elbow component. Therefore, the elbow is simply modeled as a section of pipe with a diameter that is equal to the mean of the pipe diameters at each end. Such a representation is reasonably accurate for calculation of pipe stresses as long as the reduction is not too drastic.
In this model a 12 inch pipe is connected to an 8 inch pipe by a reducing elbow. The bend is modeled with a pipe section that is an average of the connecting pipes. Next, stress intensification factors (SIF's) are defined at each end in order to represent the SIF's for an actual reducing elbow. Since the piping codes do not specify SIF's for reducing elbows, this information must be provided by the user. Contact the elbow manufacturer for information on their recommendation for SIF values.
If you are using AutoPIPE V8i 08.09.xx.xx - 09.06.xx.xx, please see the following modified approach ( based on AutoPIPE V8i 09.06.00.19):
1. Start a new model in AutoPIPE using ASME B31.1 piping code, 2012 edition.
2. At the first point in the model specify Pipe Data ID = 12STD and press OK button:
3. Specify Nominal Dia = 12.00 inches and Sch = STD:
Press the OK button to continue,
4. On the Operating Temp & Press dialog, press OK button to continue.
5. Insert Run, Dx = 6 feet, press OK button.
6. Insert Bend, radius of a reducing elbow is typically equal to a Long Elbow radius of the larger pipe size, Example: a 12x8 reducing elbow would have a bend radius equal to a 12 Long Radius Bend or 18 inches. Therefore Radius = Long.
Also, set Dx = 6 feet, press OK button.
7. Finish the bend by defining a run of pipe to A03. Insert Run, Dx = 0, Dy = -6 feet, Dz = 0. press OK button.
At this point the model should look like this
8. Insert a new Pipe Property called 8STD with 8 inch Pipe OD with STD wall thickness:
Press OK button.
9. insert a new Pipe Property called ELBOW. Enter the pipe data as shown in the figure (nonstandard nominal size: NS) based on the following averages:
Do = (12.75" + 8.625") ¸ 2 = 10.69 in
t = (0.375" + 0.322") ¸ 2 = 0.349 in
10. Select the elbow only and apply the Elbow pipe property with Modify> Pipe Properties Over Range... command, specify "Elbow" Pipe identifier:
When the "N31-14: Previously defined pipe data will be used" note appears, press the OK button.
11. Select the piping from A02 F to A03 and apply the 8STD pipe property with Modify> Pipe Properties Over Range... command, specify "8STD" Pipe identifier:
12. Move the crosshairs to point A02 N. Select Insert> Xtra Data > Joint Type and User SIF. Enter the SIF to be used at the large end of the elbow. As stated previously, contact the manufacturer for information on the SIF's recommended for the particular reducing elbow.
13. Move the crosshairs to point A02 F. Select Insert> Xtra Data > Joint Type and User SIF. Enter the SIF to be used at the large end of the elbow. As stated previously, contact the manufacturer for information on the SIF's recommended for the particular reducing elbow.
14. Finished, shown below:
Or in living color:
See AutoPIPE model at this location.
1. Because of this modeling approach the following warnings will appear when performing a model consistency check:
W726-7: Pipe diameter change without a reducer at point A02 N
W726-7: Pipe diameter change without a reducer at point A02 F
This is expected behavior and can be ignore. However very all other warning and reduce the number of occurrences to zero if possible.