Hi Nikhil,

If i understand ur question correctly, are u considering the thrust (force)coming onto the piping system if so see the direction of highest magnitude and apply that force at the concentrated point considering the direction of force. i hope this can serve ur need.

Basically the flare line will less in size compared to header, so if header is supported sufficiently the external forces may not effect ur analysis much.

Please be careful what u have selected at branch connection i mean welded t or pipe to pipe reinforcement etc.. bcoz if u have high forces coming then u may have high stress concentration at branch connection

Please correct me if i am wrong.

Thanks&Regards,
Rakesh.