We notice a difference in dynamic responses (frequency, stress) when modeling insulation using unit weight versus thickness+density. We see the same dynamic response difference in versions we have (2017, 2019)

Static center of gravity report and static output results show the same numbers for both input methods.

Using a simple cantilever model (anchored on one end, 1m long, OD=21.336mm, t=2.7686mm, material 157), the frequency from the thickness+density input matches theoretical values. Frequency using insulation unit weight input do not.


Insulation unit weight = 0.29 N/cm, Total weight (pipe+ins) = 41.7N, 1st mode f = 17.8Hz (close to f for an uninsulated pipe)

Insulation thickness, density = 51.61mm, 0.00025 kg/cm3, Total weight (pipe+ins) = 41.7N, 1st mode f = 9.8Hz


Should another insulation field be populated together with unit weight? Appreciate any help we can get. Thanks in advance.

CII considers "unit weight" and forces as FORCES APPLIED TO THE MODEL not deadweight. Thus these work arounds for weight input should not be used for piping models that will require dynamic evaluations.

Thanks Bob. This is clear.

mamak2004,

If insulation weight needs to be considered for dynamic evaluation, enter parameters only in "Insul Thk" and "Insulation Density" fields.

Development ticket is created based on your query for future implementation.

Denny Thomas
Hexagon PPM (CAS)