Problem:

Using AutoPIPE’s Tools> Model Consistency Check or when performing an Analysis you may encounter one or more of the the following messages:

• “W726-8: Kink in straight run of 90.0 at point ???”
• “W726-170:The tee at point B19 has only two legs ”
• “E801-1: FATAL ERROR : Unstable system. Need support at node ??? Dir ??

How to correct a Tee modeled with 1 segment for ½ the header and the branch piping with a separate segment connected as the other ½ of the header piping ?

Note: The highlighted section is segment D and the ½ header in grey is segment E.

Solution:

 One cause for the warning message is a tee that was modeled incorrectly. Navigate to the point in question for inspection and to correct the warning message.

AutoPIPE Tee should be constructed using one of two methods:

1. The header is one segment and the branch is a separate segment.

2. Three individual segments connected to the same point.

Note: when coping / pasting between models only the initial paste to point is connected correctly. Any additional node points will need to be connected manually using same technique below. To find all the disconnected pairs, use AutoPIPE command, “Coincident Node Tolerance (0- no check)” = (enter value > 0.00), and then "Coincident Node Checker". A report will be displayed showing all the pairs of node point with in the tolerance values that are not connected.

suggest to refrain from modeling a A Tee component as 1 segment for ½ the header and the branch piping with a separate segment connected as the other ½ of the header piping as indicated by the image above

Steps to fix this incorrect modeling approach:

1. Current point is E06. Although not necessary, sometimes it is easier to perform this process by adding a few node points near the Tee intersection
2. Using the keyboard arrows, press the left arrow (in this case) once to select the segment E side of the tee point D09
3. Press the delete button once
4. Select current point D09, verify it is now a run point, Modify> Convert Point to Run
5. Current point is still D09, select Edit> Segment> Split. The next available segment number is used ( in this case segment N) and the segment is split about node D09.
6. Select the first point on the branch, D28, again use the key board arrow, select the branch side of Tee point D09, and press the delete button once.
7. Select E06, Insert run , Add points (b) before / (a) after = Before (in this case), Name of Point = D09, press enter key or OK button.
8. Select Edit> Segment> Join. Notice that the segment has been joined and has now been renumbered.
9. Select current node point = D28
10. Insert Run, Add points (b) before / (a) after = After (in this case), Name of Point = E06, press enter key. 11. The Tee point dialog should appear, select the type of tee, and press OK button.
12. Finished. When you’re familiar with the steps this operation will only take 45 – 60 secs. Be sure to use the correct insert run direction Before / After.

Note: 

If the Consistency Check report does not present a warning or error related to a tee modeled as mentioned in the original state above, no further modifications would be necessary. AutoPIPE has a convention on the backend to distinguish header from branch for the calculations. 

One of the reasons why to fix this tee even if not required would be to clearly know what results belong to the header or branch piping.

Example:

:Tee modeled as 1 segment for ½ the header and the branch piping with a separate segment connected as the other ½ of the header piping. When reviewing the results for segment, user needs to remember that one segment is both header and branch. 

However  when Tee was modeled as 1 segment for header and separate segment for branch piping. Easier to know one segment is header piping and second segment is branch piping. 

See Also

Tee, Cross, or Branch Piping Components - Modeling Approaches

Bentley AutoPIPE