restraint loads difference

Posted by: jobcan

restraint loads difference - 05/03/08 10:19 PM

Dear all
i hav the input echo of a system and i did the same inputing as in the previous report ,same material. its high pressure 7500 psi & line temp is only 100 degree C & straight run horizontal length of around 15 or 16 meter , guide gap 0 is given .its high pressure mud pump the actual supports used are not rigid i mean it can absorb the vibration .in operating case the loads are very high and the displacement shown in the previous report is 0mm but iam getting around 10mm in the same bend . loads on the supports and on the nozzle defined stiffness in X Y Z RX RY Rz are 10 to 15 time of the previous report when i consider the default stiffness of caesar rigid support .but when i consider differnt stiffness the loads iam getting will be less but on the nozzle node its more than the allowable .expansion stress too is different. can anyone tell me wat could be the reason that iam getting different report.
Posted by: Sam Manik

Re: restraint loads difference - 05/04/08 08:45 PM

Dear Jobcan,

Please check both files very carefully once again by using toolbar "LIST INPUT". Pay attention to the red value of the pressure, temperature, ect.

Or You also can generate input echo of your second model in static output procesor, print it then compare to input echo of the first model. I think you must be missing something may be pressure, temperature, ect.
Posted by: shr

Re: restraint loads difference - 05/05/08 02:40 AM

All support act same as a spring support with very high stiffness value.
Caesar default rigid restraint stiffness is 1.0E12 N/mm.
That means if we use 1.0E12 N load that support node point will deflect by one mm. or if we arrest one mm pipe thermal movement it will create 1.0E12 N load.
Similarly if we change stiffness deflection & load also change accordingly.
Piping overall stiffness depends on line routing.
Posted by: CraigB

Re: restraint loads difference - 05/05/08 08:27 AM

In addition to duplicating the input, you need to duplicate the program control variable settings. These may not be accessible to you at this date, but if the original analyst was careful, he printed those out too.
Posted by: Sam Manik

Re: restraint loads difference - 05/06/08 11:24 PM

Dear Jobcan,

Yes, like mentioned by CraigB if we assume the input piping already OK then pay attention to the setup file and control parameter : friction stiffness, translation and rotation stiffness, ect. If he did not print it in input echo>input listing option then comparison is not valid.