When you have difficulty extracting a line, the first thing you should do in analyzing the problem is to sketch out the network. Often this is enough to identify the problem. If the structure in section 4 of the report is incorrect— that is, the topos are not correctly defined and connected or the pointers appear incorrect— then PDSTRESS’s input will be wrong and the drawing will definitely be incorrect.
When the data structure represented in section 4 of the report is incorrect then you can conclude that either the interface has a bug or there is a problem in the model. Typical model problems include such things as disconnected sections and overlapping components or pipes.
When the modeler has inadvertently placed two pipes on top of each other you will get an error message at the top of the HITS report stating this. The message will also report a node number where the problem was detected. By getting the coordinate of the node you can pinpoint where in the model the problem occurs. This can also occur where the connect points of components overlap each other and are not properly connected.
Notice that one of the columns in section 4 of the report is called section. In a correct network all of the topos should have a value of 1 in this column. When the network is composed of multiple disconnected sections, however, some topos will contain a value other than 1. In this case the network for each section should be sketched out. It should be apparent after doing this where the different sections should have been connected in the model and, therefore, where the trouble spot is.
Another problem that might occur is that components that should all be colinear are not. This is detected by examining the direction list number. If the direction list changes for example from one pipe to another then a problem exists in the model and the line cannot be extracted properly.
Mismatches between the design file and database can also cause iso extraction failures but these types of problems should be trapped and reported adequately in other areas of the software. You should not need to rely on the HITS report to find these kinds of problems.
When the data structure in section 4 of the report is correct then the traversal in section 5 should be examined. Even if the network is correct, some other bug can cause the network traversal to fail. Again, if the traversal is incorrect then PDSTRESS will definitely fail. When both the network and the traversal are correct, there is most likely a problem with PDSTRESS.
When PDSTRESS is at fault, then one of the following scenarios is true:
The drawing appears correct for the most part but some aspect of it is incorrect.
When this happens there is usually some option or combination of options that have been enabled that resulted in the problem. The best way to find the cause of the problem is to start with a basic drawing generation setup that contains few "special" options. Then add a few options at a time until the problem is reproduced. Finally, through a process of elimination identify the option that is causing the problem. All failures of this type should be reported to Intergraph.
The drawing or one sheet of it is scrambled— a total failure. When this happens it is usually the case that disabling options will not result in the drawing working— though sometimes it does. The best thing to do when this happens is to try and reextract a smaller portion of the line if possible. The failure should also be reported to Intergraph.
When any sheet of a PDSTRESS drawing fails, ALL sheets from the same pipeline may contain errors and are suspect.