Creating one of the pipe sections

Choose Files->New, thus starting work in a new file.
Rename the layer 'Layer0' to 'pipe1' and create two new child layers "inner" and "outer". Set 'pipe1//inner' as layer to use with a <Double-click>
Choose Geometry->Create->Point and enter new point (0, 9)
set 'pipe1//outer' as layer to use and create the new point (0, 11). Press ESC to conclude the creation of points.
From the Copy window, select Points and Rotation. Enter an angle of 180 degrees and from the Do extrude menu, select Lines. The axis of rotation is the x axis. Enter two points defining the axis, one in First Point and the other in Second Point, for example, (0, 0, 0) and (1, 0, 0) , check Maintain layers, and set Multiple copies to 2.
Click Select and select the two points just created. Press ESC.

The current model

Create a surface: choose Geometry->Create->NURBS Surface->By contour and select the four lines. Press ESC twice.
From the Copy window, choose Surfaces and Translation. In First Point and Second Point, enter the points defining the translation vector. Since the pipe section must measure 40 length units, the vector is defined by points (0, 0, 0) and (-40, 0, 0).
From the Do extrude menu, choose the Volumes option, and set Multiple copies to 1.
Click Select to select the surface. Press ESC to conclude the selection process.

Creating a pipe by extruding the ring