Thanks Richard for your answer,

I like the idea of having the possibility of multiple sessions, Because it save a lot of time when you revise two models. You can work with two model and prove two things one time in two model differents.

Other idea, work with specifications (piping class)
If i can define specifications about diameter and schedule and the specification change would be easier change the conditions. (In the last versions Caesar 7.0 did one thing, allow change the diameter, thickness, temperature, graphicaly and is very usefuf, but if further i could create a specification the work would be easier and the posibility de wrong would be more difficult).

Example

Create de specifications:
A131 24" --> i define A131 24" is diameter 24" and schedule std.

A331 24"--> i define A331 24" is diameter 24" and shedule 80
When i start with one line, i could choose the specification (that come of my piping class), and then it would be easy revise my model is corretly introduced.

Thanks in advance.