Dear all,
can anybody tell me which one is of more importance in regards to interpret and forecast the results of particular location by noting the values at some other near location in the whole piping system; Local Force or Global Force ?

Also, i have noted that :

Local Fz = -Global Fy
Local Fy = Global Fz

Plz anybody can explain this ???

For any given piping element, you have a set of end forces and moments i.e. the free body diagram. Now these forces and moments can be aligned with the local coordinate system of the element or the global coordinate system of the model. The forces and moments acting on the element are the same, but the difference is in how you identify the values.

There is a big write up on this topic in the Technical Reference Manual.