October 7, 2014

Reverse Pressure Pipe Network Slopes in Civil 3D

Our tech team at Ideate recently came across an interesting request from one of our customers. They had created a Pressure Pipe Network in Civil 3D, and after completing the design, realized that the slopes were being calculated in the wrong direction. 

For those unfamiliar with the Pipe Network and Pressure Network creation process, a “direction” is specified in the initial steps. When generating a Pressure Network, I never really thought of this as much of a factor, since a pressurized system technically has no direction. What I did not consider, is that the direction specified also plays into how the Civil 3D labels calculate the pipe slopes. If a Pressure Network is created with the same direction as the Alignment it is referencing, the slope appears as shown below. 

Based on the screenshot, we can clearly see that the road slope in the profile is displayed at -4.00%, yet the pipe slope in the pressure network shows 4.05%. If this was the case with a gravity network, we could easily use the Change Flow Direction option to correct it. Unfortunately, Pressure Networks do not include an option to change the flow direction.

So what can we do? One option is to delete the network, and re-create it with the proper direction specified up front. After some testing, we found that if the direction selected was opposite from the alignment, then the pressure network labels appeared correctly. When creating Pressure Networks from Objects, the direction opposite the alignment had to be selected. When using the Pressure Network Creation Tools, the network also had to be drawn opposite the direction of the alignment.

If the network is large enough, re-creating it from the start is not a very efficient solution. In that situation, we can use an Expression in the Pressure Pipe Label to “reverse” the slope calculation.

First, we’ll need to start by adding the Expression under the Toolspace → Settings tab → Pressure Pipe → Label Styles → Expressions collection. 

 Right-Click Expressions and select NEW.
  1. Provide a Name and Description.
  2. In the Expression box, add a minus (-) symbol.
  3. Use the Pre-defined Properties list to add the Pipe Slope property to the Expression following the (-).
  4. In the “Format result as” box, select Percent.
  5. Click OK to exit.

Our next step is to add the custom Expression to a new Pressure Pipe Label Style. 

  1. Right-click on the existing Pressure Pipe Label Style (in this example it’s called Standard) and select COPY.
  2. On the Information tab, provide a new name (Reverse Pipe Slope).
  3. On the Layout tab, click in the Text Contents cell to access the Text Component Editor.
  4. Delete the existing content in the Text Component Editor.
  5. Select the “Reverse Pipe Slope” expression from the Properties list.
  6. Specify the precision, then click the Arrow to add the expression as the content for the label 
  7. Click OK to exit the Text Component Editor, and OK again to exit the Label Style Composer. 
The final step is to apply the new label style to the Pressure Pipe segment. If  the pipes are already labeled: 
  1. Select the segment label, and access Label Properties.
  2. In the Label Properties, select the new style from the Pressure Pipe Label Style list.

The updated label now displays the slope in the same direction as the road profile. This can also be done to multiple segments at one time by selecting multiple labels before accessing Label Properties. 

If pipes are not labeled, be sure to select the new reverse slope label style when adding segment labels to the profile view. 

So, until we see an option to Change Flow Direction added to Pressure Network editing features, we have an easy way to reverse the slope calculation using an Expression. This can also be added to a Civil 3D template (.DWT) file just in case we run into this problem on a future project.

Matt Miyamoto, P.E.
Ideate AEC Application Specialist

Matt is a licensed Civil Engineer in the state of Hawaii. Matt obtained a BS in Mechanical Engineering from the University of Hawaii at Manoa, and has 7 years of private sector design experience which he applies in his role as an application specialist with Ideate, Inc. His project experience includes residential and commercial site development, private and public sewer, water and drainage systems, harbors improvements, and roadway improvements. While in Hawaii, Matt was involved in multidisciplinary projects for City and County agencies, State Departments, the Army COE and private developers. @MattM_PE

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