Thanks Dave for your reply,

Agree with you dave. Two directions are two seperate events. First direction force is may be positive impulse load and second direction may be negative impulse load.

If we are considering the both positive impulse load and negative loads we have to apply two direction forces at seperately on the elbows these are due to pressure immbalance between elbow to elbow pairs.

This is clear. But after reading your old post title SURGE LOAD, Date- 10/15/07 " I seems to me that either approach would work - either define the calculated load on every elbow where only one elbow load changes at a time or just apply the imbalance on each elbow-elbow pair. The first approach uses the steady-state plus the transient and the second applies only the transient. I think the second is simpler."

Please find the attachment of the sample calculations of forces from both approaches.

In my calculation, first and second Approach force values are varies.

Please correct me, Where my calculations/understanding gone wrong.