Dear Members,

As of all your reply is acceptable for the piping system inside plant, where the displacement are limited to max of 100 to 125 mm.

But in case of pipeline system (for example, Pumping station), for a bend of 20D elbow, normally the displacements are limited to 300 to 350 mm. To limit the displacement near the small bends (i.e.) cold bend of 40D, PGB's such as Pipe Guide near Bend is provided to limit the displacement.

Please refer following cases,

Case-1 - Supports with friction for all support elements,

+y with 0.3,
Guide with 0.3 and

The loads on supports are Fa = 7.8 kN, Fl = 12 kN and Fv = 13 kN,

My query is since there is no axial stop in the support to limit the pipe in axial direction, why there is a huge axial load on the support. We had a doubt, if there is no axial stop, then the max. axial load on support due to friction shall only be 0.3 * Fv = .3*13 = 3.9kN but why the result shows 7.8kN. After many checks with the same kind of friction effect on support elements, it is seems that the Caesar-II calculates the axial load due to friction for support elements without axial stop as

Fa = 0.3*Fv + 0.3*Fl = .3*13 + .3*12 = 7.8kN (if friction is specifed for all support elements).

Case-2:

If the friction is specified only once in +y with 0.3,
Guide (Leaving friction coeff. blank), the axial load is calculated as

Fa = 0.3*Fv + 0.3*Fl = .3*13 + 0*12 = 3.9kN.

From the above it is seen that there is huge variation in the force in axial direction, the change in force due to friction effect creates a huge variation in the cost of support.

So i conclude, to be conservative it is better to go for case-1 type friction effect on support elements. Since if the support is designed for Case-2 (i.e. for 3.9 kN), after many displacement effect there is a more chance for the support to fail.

Even in Mr.Peng articles, he is advised not to neglect the effect of friction.

If my conclusion is not acceptable, please clarify.....