Hi,
It sounds like you need to model the "end conditions" for your system. If the system ends with a flange going into a skid then I guess you need to model the flange pair and an appropriate amount of piping beyond that.

To find out what the loads are at the flange pair you can use a "connect node anchor" located between the flanges (where there would be a gasket) and this will give you the loads, moments and movements at the flanges which hopefully will be within the "tie-in flange loads" that you have.

If you are lucky, for your end conditions, on the other side of the flange pair as it goes into the skid, there will be an anchor. I call this a "battery limit", you are normally responsible for the piping up to the battery limit and said nozzle/flange loads. The skid vendor is responsible for the piping beyond the battery limit which is inside the skid. So you only need to model the skid piping as far as the anchor, nice and simple.

If you are not so lucky, then for your end conditions you will need to model some of the piping within the skid, so you'll have to get the piping isometrics and pipe support types and locations from the skid vendor (or go and do a survey of the piping yourself if you have access to the skid). You'll have to use judgement based on the skid piping layout as to how far into the skid you model the piping to generate representative "tie-in flange" loads from your end condition piping.

I hope that helps,
regards,
Winnower.

This is a problem that comes from coordinator of the piping project. Normally, if the continuous piping project was split into several contract the interaction points need to be discussed, and adequate determined loads and displacement should be given to the vendors.

IMO you, as vendor, need to discuss this with the coordinator and get these permissible loads and displacements at tie-in points. Tie-in points for skid might be a flange face, as in your case, the flange loads and displacements should be given to you. Please be aware that these loads and displacements should not fail the flange connection.

In case the coordinator of the piping project is not aware of this, you need to ask the coordinator bring the parties together and agree on these loads and displacements face to face and make it writing.