SADDLE CACULATI0N

Dear Codecalc,
I will appreciate if you answer my comment on Pvelite.
Am I right or wrong?
In the calculation of saddle, Pvelite calculates reaction forces due to wind or earthquake as following:
Fwl = Max( Fl, Friction Load, X Forces) * B / Ls
My comment is that the above formula must sum Fl and X forces; that is,
Fwl = Max( Fl + X Forces, Friction Load) * B / Ls, as Pvelite does it in the saddle reaction forces due to Ft (Ftr * ( Ft/Num of Saddles + Z Force Load ) * B / E)
Because Fl and X forces have the same nature. Both are external loads, so their equivalent force (F = Fl + X forces) must apply on saddle.
I hope that my comment is clear.
Regards,
Naderi

Dear Naderi,

According to me you are absolutely correct.

In such a case you can input forces along x direction as sum of wind/seismic force along x & whatever additional Fx you wish to consider.

Thus this Fx force will be greater than wind force.

Hence the saddle analysis will be done for the combined load.

Dear Naderi,

Your observation is correct. The program assumes that a X-direction force (axial) for a horizontal vessel is a non-operating force such as a heat exchanger bundle pullout force or transportation force. Chances of the worst wind/earthquake occurring at the same time are very rare. As typically done in the these calculations maximum of these conditions is taken.

But, if you have a large loads acting on a nozzle located on the head of a horizontal vessel. Then this operating force should be added to Wind/Seismic. In this case you can use the workaround suggested by Mahesh.

We will try to address this in the software. One thought is to use check boxes on the Loads Dialog that indicate if a particular load needs to be combined with Wind/Seismic.

Btw, what is source of the X-forces that you are applying to the vessel?