Hi Cleiton,
Can you post an example of one of your models in trouble? It would help to know where is the problem.

Thanks for your reply.

The file is in the link below.

tank-basic.mo

Every element of your model coming from Modelica.Fluid needs the specification of the Medium used. In OMEdit it can be done, from version 1.16 I think, using the graphical interface. In the tab 'General' you can select the Medium from the compatible ones charged. Another normal way is to define an alias for a Medium in your model, and make the Medium of each element equal to this alias. I have used both ways in a modified model.
You have connected an external source to the port  T_in of boundary1, but 0.1 ºK doesn't seem a reasonable value, so I think that you probably wanted to specify 0.1 kg/s for the port flow, and I have changed the connection to the m_flow_in port. Nevertheless you need also to specify that you want to take the value received via the connection by checking the box 'use_m_flow_in'.
For the flow characteristic of the valves you have left the default value of OpPoint. In this case you need to give the operation point, this means to fill the nominal pressure drop at the nominal flow, with the nominal opening. In one of the valves I have changed to Kv and specified the Kv of the valve. It was also necessary to supply the apperture to the valve connectors.
In order to better follow the evolutionof the tank I have specified a simulation time of 3600 s.

ModelicaTest34.mo

You will need to erase the lines:

  annotation(
    uses(Modelica(version = "3.2.3")));

at the end of the package, that have been added automatically because I  am using Modelica 3.2.3 and not 4.0.0

Ok, thanks for your help!