Circular Duct Stress Analysis

Hi all,
I was wondering if Caesar II is capable of doing stress analysis of circular ducts in petrochemical and mining refinery plants. If yes, what is the applicable code(s).

Thanks in advance,
MAGA

You'll likely run into issues due to the thin wall nature of most duct. The plants you're working with should tell you what code(s) they're designed to.

From an FEA viewpoint, yes c2 can perform the analysis. This will yield displacements, restraint reactions, and element forces. However, as noted above, the stresses may be suspect due to the thin-wall nature of your system. The B31 codes warn you against D/t ratios above 100.

Piping flexibility analysis assumes the cross-section will not change under load - in other words it remains circular, and overall behavior is dominated by bending. If these assumptions are not valid, neither are the results.

Thanks Richard and anubis512 for your reply.

Cheers,
MAGA

Thanks Richard and anubis512 for your reply.

Cheers,
MAGA

Hi Maga,

You can use FEA tools for a more applicable data. This will consider the flexibility factor K & Stress Intensification Factor SIF's at the fittings (e.g. bends, tees). If the D/t ratio is less than 100 you can consider ASME B31.J & if more than 100 you can use FEA. In this case, the limitations of beam models can be addressed by using this tool.

Please correct me in case I've made a wrong statement.

Cheers!!!

Just take note that FEA also has some mathematical limitation which is not a closed form solution unlike direct stiffness method being employed by most of pipe stress programs. In FEA, you must check if you have enough mesh density & check if your solution converged to a reasonable value. But take note of the sharp corners, which causes singularity & stress going to infinity. Normally, you can do a stress convergence study at the toe of the weld which is mostly where fatigue failure occurs. This is useful where there is a potential for fatigue. Some consultants have extensive fatigue testing to validate FEA software.

Any other opinion is highly appreciated.

Cheers!!