The following example is taken from Rowell and Wormley, System Dynamics: An Introduction, Prentice Hall, 1977, Example 5.6, pp 141-143.  The example consists of a fluid tank system fed from a long pipe significant fluid inertance and resistance.  In this simple example the pump is modeled as a pressure source.  The system, together with its linear graph and normal tree, is shown below:
 

Specification to Maple-SYREP in terms of the individual elemental equations, and the compatibility and continuity equations as derived from the normal tree, is shown below.  The elemental equations are written using "dot()" to indicate the derivative.

The constraint equations are formed by:
1)  Replacing normal tree links (one at a time) and writing the loop (compatibility) equation.
2)  Summing the through-variable (volume flow rate) at the nodes within the dotted circles.