Hi,

I have recently been doing some work checking nozzle loads and have some discrepancies between a manual check (using WRC 537) and CAESER's WRC 107 analysis.

In order to perform the calculation one must look up an appropriate curve for a given Y and p value. If the value for Y and p lies between two curves interpolation must be done.

When performing calculations for spherical vessels I am finding that CAESER is correctly interpolating the Mx and My values but seems to be performing no interpolation of the Nx and Ny values.

For example using a Y,p and U of 5, 1.5 and 0.6957 respectively one would expect to interpolate between curves SP2 and SP3.

Y p Figure No.
5 0.25 SP1
5 1 SP2
5 2 SP3
5 4 SP4

Calculating exactly the values from curve SP2 for the above figures gives:

Mx My Nx Ny
0.060521209 0.022222664 0.055773262 0.110052459

and calculating SP3 gives:

Mx My Nx Ny
0.032182278 0.033857187 0.634780828 1.579903917

you would then interpolate to give:

Mx My Nx Ny
0.046351744 0.02804 0.345277045 0.844978188

CAESER II gives the values as:

Mx My Nx Ny
0.04826 0.02834 0.06080 0.13621

As you can see CAESER appears to be interpolating the M values to give good agreement with the manual check (the minor discrepancies in values are acceptable errors as I roughly got the U p and Y to match in CAESER etc). The N values however are clearly way off and not interpolated.

I have not checked cylindrical yet but perhaps someone can confirm the approach?

Kind Regards,

Nick