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General SewerCAD [FAQ]

Product(s):	Bentley SewerCAD
Version(s):	08.11.XX.XX, 10.00.XX.XX
Area:	N/A

How can I export my model to shapefiles?

This can be done in the flextables for each element type, using the Export button in the upper left corner. For example, open the conduit flextable and click Export to export your conduits to a polyline shapefile. Click the Export button in the manhole table to export your manholes to a point shapefile.

Converting your model elements to shapefiles

How can I filter a flextable on selection set?

To filter the flextable to only show elements included in a particular selection set, you can use one of two methods:

First, select the selection set in drawing by double clicking on its name in the selection set pane. Then, open the flextable pane by going to View > Flextables, right click on the table of choice (pipe report for example) and choose "Open on Selection". The table will only show elements that are part of the selection set.
If you have version 08.11.01.21 or greater, double-click your selection set to highlight in the drawing, then right-click anywhere in the drawing pane, choose "Edit Group" and open the flextable of choice.

How can I filter the Sanitary Load Control Center based on a selection set? I only want to see load entries for nodes included in a particular selection set.

See the following support solution for details:

Filtering the Sanitary Load or Inflow Control Center by attribute or by selection set

Why do I sometimes have a pipe whose calculated depth is below the crown, yet the "capacity (flow / full flow)" is above 100%?

Using Manning's equation as shown below, SewerCAD calculates the Capacity (Full) of a pipe. The Capacity (Full) is based on assumption that the flow through the pipe is absolutely at normal flow condition and the normal depth equals the rise of the pipe (for circular pipe the rise = diameter)

Q = k/n*A*R^(2/3)*S^0.5 [Manning's Equation]

At normal flow:

     •     The water depth, flow area, flow, and velocity distribution at all cross-sections and throughout the entire length of pipe remains constant.
     •     The Energy Grade Line (EGL), Hydraulic Grade Line (HGL) and the Channel Slope are parallel.
     •     The velocity/depth ratio is constant.
     •     There is no acceleration or deceleration of the moving mass.

However, in SewerCAD, water does not flow at normal flow; it computes a varied flow profile. So, the HGL slope can be changing over the length of the pipe and thus depth can be different than normal depth and this "full capacity" value may not be good for comparison.

Now, in a SewerCAD model, increase the length of the pipe whose Flow is exceeding the Capacity (Full), say by 10 times and then look at the profile of that pipe. You will notice that the upstream end of the pipe may flow full (surcharging). If not, increase the length of pipe.

What this means is, the initial pipe length is not long enough to create the surcharge even though the Flow exceed the maximum capacity and therefore the HGL in the profile is not above the pipe crest elevation.

Why do I get "Unable to solve network hydraulic equations" or "Network Unbalanced" when computing a model with several air valves?

Because air valve status can change, they can lead to instability in the model especially if there are many air valves in the system. To improve the stability of the model, it is desirable to force some of the valves closed. This can be done by setting the property "Treat air valve as junction" to True for those valves that are expected to be closed anyway.