Hello all,

I have a question or two regarding the conical tank connection stiffness calculation.

Here is my problem. I have a short length of pipe that connects to the bottom of a conical tank nozzle. It is a 17" long 2" pipe connecting to the tank. After a 90 degree turn, the pipe reduces to 1" and is routed approximately 5' to 5.5' to a pump nozzle. The temperature of the pipe is only 100 degrees F at 33 psi. Even at this low temperature, the minimal pipe expansion on this rigid section of pipe causes forces and moments that are too high for the pump. We believe that if we can model/input the stiffness of the conical tank connection, that would absorb the minimal pipe movement and reduce the forces on the pump considerably.

First, is there a way to determine the stiffness of the conical nozzle or input the conical portion of the tank through Caesar II?

Second, if Caesar II is not able to model this conical tank, is there a accurate means to calculate this by hand?

Thank you

CAESAR II will only determine nozzle stiffnesses for WRC297, API650, and PD5500 nozzles. For other types of nozzles, you'll need to obtain the stiffness values from some other source (the vendor, or FEA).

You can't model a conical section in CAESAR II. Everything is a "3D Beam", of constant cross section.


Not that I'm aware of. I would suggest the FEA route.

Geoff,

The conical nozzle or conical tank bottom might be approximated by series of elements with stepped diameters from small end to large end. The thermal growth of tthe elements would provide a fairly accurate displacement. The calculated flexibility would be less accurate. It may depend on the relative flexibility of the piping versus the conical tank connection flexibility. Compare the cone diameter to the piping diameters for judging the contribution of cone nozzle flexibility.

The pump inlet with Nps-1 piping must have a very small allowable load. I would recommend adding flexibility by routing the line with two more ells and offsets in direction to reduce the piping loads on the small pump.