| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Environment: | N/A |
| Area: | Graphics |
| Original Author: | Bentley Technical Support Group |
| Date Logged & Current Version | Aug. 2016 10.01.00.09 |
Problem:
The color plot about a tee seems to be wrong, see image below for example:
Why and how to fix it?
Solution:
Review tee and then elbow.
Tee Analysis:
Let us first look at the construction of the Tee based on segments, View> Show Options> Segments color plot:
As one can see the tee is made up of 2 segments (ex. H and P).
H segment = 1/2 the run of a tee and the branch of a tee
P segment = 1/2 the run of a tee
This modeling approach is OK and the stress values are calculated correctly.
Note: check the Model Consistency report to see if any warnings are related to this issue. The following Warning was found:
W726-7: Pipe diameter change without a reducer at following point(s)
B06, F06, G06, H07, P02
A better approach would be to model the entire run of a Tee with one segment and the tee branch with a separate segment. See the following WIKI page here to alter the modeling approach.
See updated modeling approach segment color plot below:
Now re-run the analysis and check the new color plot:
Again the calculates stress results are correct:
Note: the high stress is actually on the Branch of the tee (ex. Seg Q, H13), compare this information to the original modeling technique where the high stress was located on branch portion of the tee node point (ex. H07+). Confirmation that the results are identical.
Question: Why is the new modeling technique color plot so different compared to the original color plot image above?
Answer: The Header segment is hiding the complete color plot near the connection point (ex. H13). To better understand, hide the header segment (ex. H) to see the true color plot for the branch segment (ex. Q):
Elbow Analysis:
Similar to the Tee analysis above, start by creating an report of the node points around the elbow.
This is a good example of how the code stresses can drastically change from side of the node point face to the other, mainly speaking from the +ve (upstream) side of the node point compared to the -ve (downstream) side of the same node point. ..
Example:
F43 F- = 18507
F43 F+= 48055
Question: What is the main reason for the drastic change in the code stresses at the same node point?
Answer: First note the node point location, is it on straight pipe or at a junction point for a piping component? Recall, piping components have higher SIF compared to straight pipe. In the example above, looking at the reported values for each side of the node point; Ma, Mb, Mc, Eq No, Load type are comparatively all the same. However, as suspected the SIF was found to be severely different. Thus leading to huge difference between values and consequently a sharp change in the color plot as indicated here:
Conclusion:
There are more than one way to model a Tee in AutoPIPE. Both modeling approaches calculate the same stress results and display color plots correctly. Due to the graphics engine in AutoPIPE the first modeling approach displayed the color graphics on both sides of a node point that was 1/2 run and branch of a tee. The second modeling approach where one segment is the entire run of a tee and another segment is the tee's branch is a better modeling approach to reduce the number of warnings in Model Consistency Check report and to better display code compliance color plots.
With regards to elbows, reducers, other piping components, code calculations can abruptly change around a single node point or in a very short section of piping. To better understand why a color plot has abrupt changed in color, start by investigating the reported calculated code stresses as demonstrated above.
See Also
See WIKI here item #2 for additional methods of modeling a TEE / Branch connection.