Routing Exceptions

If, for any reason, the AutoRouter cannot route a pipeline segment according to its rules, that pipeline becomes an exception pipeline. To have minimum impact on material takeoff reporting, the AutoRouter will first try to create the shortest failed route calculated.

In the unlikely event the router cannot calculate any route for a segment, it will create a minimum Manhattan route for the segment it could not route. A Manhattan route is the shortest orthogonal route between the endpoints. Primarily, the only time the router has to default to a Manhattan route is if one or both of the pipe’s endpoints is outside of the routing volume. Because the routing volume is bound by grade and the obstacles within the model, an endpoint outside of that volume would, most likely, be below grade.

Each failing aspect of a pipeline route will be reported in the Exception List and the pipeline will be drawn on the exception level of CAD – unless you override that setting.

Cable Exceptions

Exceptions that can only be applied to cables refer to cable rather than pipeline. However, as most routing exceptions can be applied to both cables and pipelines, they do not distinguish between the two, using pipeline in the text of the message.

Common Exceptions

All of the AutoRouter’s exceptions are documented in "Routing Exceptions"; some of the more common exceptions, however, are documented here.

Exception	Description
Connectivity	If a pipeline is not fully connected, it will generate an exception. Another exception generated by connectivity is a diameter inconsistency. Connectivity problems are reported in the Check report as discussed in Checking Connectivity. The Check report can be run before routing so that you can correct these sorts of problems early. Another exception caused by connectivity is for an unknown reducer size. This exception is generated when the reducer has been sized to the same diameter as the upstream segment. This reducer will need to be deleted and a properly sized reducer added to the pipeline.
Pockets	Non-pocketing lines generate an exception if they cannot be routed without a pocket. PlantWise has some basic rules for what types of pipes should be non-pocketing (see "Non-pocketing Pipes" in Router Initialization ); however, you can turn the non-pocketing attribute on or off for any pipeline via the Pipeline Editor. To resolve pocket exceptions, the should evaluate the layout of the pipeline’s endpoints to insure a non-pocketing route is possible. If that is the case and the router cannot find a non-pocketing route, then the line should be manipulated (see "Segment/Point Manipulator").
Interferences	If the pipeline begins or ends within another object, or the router’s search is unable to find a clear path, then it is possible for a pipeline to interfere with any other item in the model. In general, interferences occur in crowded areas of a model and layout alternatives should be considered. If the layout is locked, changing pipeline attributes as well as manipulation of the route are always options. See "Editing Pipelines" for more information on these methods. To assist you in locating interferences, you can use the Toggle Interferences command from the"Pipeline Editor" or the "Exception List". Steel – There are several reasons a pipeline may interfere with a steel member: the piperack geometry; an endpoint of the line could be placed too close to a steel member; or, the area is over-crowded. Commonly, if a pipeline is interfering with a pipeway member, the pipeway is undersized and the capacity of the pipeway should be evaluated. However, other pipeway situations that can result in interferences include: elevation changes between perpendicular pipeways; insufficient space between pipeway levels for large diameter pipes; obstacles in the pipeway; branching pipeways that straddle a column of the primary pipeway; and, width changes between pipeway sections. You can also force a pipeline onto another pipeway level from the pipeline’s editor. Otherwise, the placement of the equipment and/or nozzles may need to be re-evaluated. At times, it can be difficult to locate the steel member in question. In that case, the option to Highlight Interfering Components from the Exception menu of the Exception List dialog can be very useful. Pipes – Pipelines that interfere with each other, or themselves, are generally on an overloaded pipeway or in an otherwise crowded area. The size of the pipeway and/or layout of that region should be examined. Vicinity Routing Rule – All equipment instances have vicinity routing rules either defined by you (see Defining Equipment Vicinity Routing Rules) or by the minimum distance needed to exit a nozzle and make a turn. If the user-defined rule would route a pipeline into another obstacle, the AutoRouter will calculate a shorter path and generate the exception: "There are likely interferences with the vicinity route provided for end <equipment/nozzle>; reducing the vicinity route to the minimum possible." It is possible that the new route will not have any other exceptions; however you may want to examine the pipeline to be sure the path calculated by the router is acceptable. To graphically examine a vicinity route, you can use the Display > Toggle Vicinity Routes menu of the Pipeline Editor or the Equipment Editor. This will turn on a line that follows the path of the prescribed vicinity route. If the minimum distance needed to exit a nozzle interferes with an obstacle, then the placement of the nozzle, equipment, or the other obstacle should be re-considered. Any error in the vicinity routing rule will also result in exceptions. You are alerted to errors in vicinity rules each time the rule is Accepted. When these errors are corrected in the rule, the exceptions are avoided. Equipment – If a pipeline is interfering with an equipment obstacle, the region is probably crowded and you should look at layout alternatives. It is also possible that the equipment’s obstacle boxes are not properly sized. To view obstacle boxes, select Display > Toggle Obstacle Boxes menu of the Equipment Editor. Obstacle boxes can be edited in the geometry rules for the equipment’s class definition or for the specific instance. (Geometry rules are discussed in Defining Equipment Geometry .) Nozzle Take Off – A volume of space is reserved in front of each nozzle so that the connecting pipeline has room to exit. If another line is interfering with that take off it is likely that the pipeline is attached to another nozzle on the same piece of equipment. In this case, nozzle placements should be examined. Other Obstacles – If a pipeline is interfering with an obstacle, the area of the model is likely to be crowded and you should consider layout alternatives. Other Settings – If there are router interferences that cannot otherwise be explained, it is possible that a pipeline setting is causing a problem. The most common of these settings are insulation thickness and Minimum line spacing. Insulation adds thickness to a pipeline that has to be accommodated during routing. Because the fully insulated diameter of a pipeline is not shown by default, this pipeline attribute can be easily missed. To see the full pipeline diameter, you can Show Insulation via the Pipeline Display Preferences dialog (see "Pipeline Display Preferences"). Minimum Line Spacing is a Project Setup variable (see Site Constants) and is the amount of space must be between a pipeline and any other component. Any breech of that distance will cause interference exceptions.
Routing Below Grade	Pipes that route below grade are likely to be attached to nozzles that point down and do not have enough clearance to make the necessary turns to avoid grade. In that case, nozzle placement or equipment location should be reconsidered.
Missing Data Table Entry	Many aspects of routing are based on table data; therefore, missing data is going to generate an exception. In many cases, the router can assume a value (such as flange width) or use a default value (such as a straight tee). The only way to eliminate these exceptions is to provide the data table with the missing information.
Undersized Pipeway Level	If a pipeway level is too narrow to accommodate all the pipelines that are supposed to be on it, multiple exceptions will be generated. First, there will be an exception on the pipeway indicating how much space is needed on each level and how much space is actually available. If you have edge space and/or inside drop zones, the available space on any level will be less than the width of the pipeway. Second, for non-required pipeway levels, the line may be placed on a different level and that exception reported. Finally, there will likely be additional exceptions on the pipeline if the router has to run it through members of the pipeway or into other pipelines. Making the pipeway wider, adding levels, reducing or eliminating edge space, and outside drop zones are the best ways to increase the available space of a pipeway level. You can also require lines to a different pipeway level by changing the PW Level Required attribute to YES in the Pipeline Editor. Another cause of an over-loaded pipeway level is that pipes that could be routed directly are going to the pipeway. You can override the choice to go to the pipeway by changing the Category of the pipe in the pipeline’s editor.
Wrong Pipeway Level	One pipeline attribute defined by the Commodity Code is the preferred pipeway level. If there is insufficient room on that pipeway level for the pipeline, the router will place it on a different level and generate and exception. If the pipeline route on the alternate level of the pipeway is acceptable by you, the exception can be ignored or suppressed (see "Suppressing Exceptions"). To remove the exception altogether, you can change the Pipeway Level setting in the Pipeline Editor to `any`. If the pipeline must be on the preferred level of the pipeway, you require the line to any pipeway level by changing the PW Level Required attribute to YES in the Pipeline Editor. It is important to note that requiring a line to route on a specific level of the pipeway can result in the overflow of a different pipe to another level of the pipeway. Pipelines being overflowed to different levels of the pipeway indicates that the size of the pipeway may not be sufficient. You can also change pipeway level names and order from the Pipeway Builder to better accommodate pipelines. For more on pipeway level names, see "Editing Level Names".
Insufficient Space for Inline Component	There are times when the length of the pipeline, or pipeline segment, is insufficient to accommodate an inline component or its spacing requirements. In such cases, the inline component is placed and an exception generated with the actual location of the component. Depending on the situation, there are several ways to accommodate the inline. move other inlines that are not allowing for enough space for other components (e.g. placeable inline components); move one or both of the pipeline’s endpoints to generate more pipe length; manipulate the pipeline to accommodate the inline component; or if the inline is a user-defined inline, change one (or several) of the following attributes: length, segment preference, or upstream and/or downstream spacing.