Thanks Ibrahim, but the case like my first post is client ask to do stress analysis due to this pump start up because they are worry about the load effect to The "SPlit Tee" they are using after Tie in Process. Yes indeed they are right, load at the Split Tee connection is very high.
I have finished the simulation using Boss Fluid and perform stress analysis using CAESAR II. and i have this 2 scenario as i mentioned above, that is:

1. First, there will be Slug phenomena and Surge.
2. Second, only Slug phenomena that will be considered.

Some of engineer that i met, told that they have experienced with this case also and they are usually will only considered slug flow that will occur in these condition.
In Boss Fluid Manual also there is an example of this pump start up filling an empty pipe and it suggest to considered only slug flow.
But there are few papers and experiment by Kolp and Martin CS that mentioned that surge will also likely yo occur in these event.

So, my point here just to make justify whether there is among of Our Fellows here that have an experience with Pump Start Up case, and which approached that they usually used.
Thanks.

Rgrds
TS