Dear stress experts,

I am currently working in FPSO Topside facilities.I have some query related to above topic.
1.i.e Dynamic Acoustic-pulsation analysis of triplex reciprocating pump and piping.

Query: can we perform this in caesar-II by using beam method applying simple wave theory?

2. As far as controlling the vibration in the piping is concerned: we can make a static model of piping system and incorporating the support stiffnesses in it.And selecting support spacing & type by 4 th harmonic frequency method.Then passing the same in thermal analysis(static) and vibration separation in modal analysis(dynamic).(refer Mr. Ghosh choudhury's document in Hydrocarbon processing "decreasing vibration in reciprocating compressor piping").

Query:Is modal analysis provides 4th harmonic natural frequency?,If yes then how to identify this?

3.I need to condsider pulsation effects into the model.Also
I need to do vibration separation in pump foundation,Pump crank,pump and piping system.

Query:How to do this in a caesar-II dynamic analysis module?

Valuable suggestion towards progress is always appriciated by the world.

Dear Paul,

You can do your study with CAESAR II but I think you should divide it in two stages.

First of all you have to determine the natural frequencies of your pipe through Modal Analysis and then move support or add snubbers to achieve the frequency you want for your configuration.

In a second stage you have to analyze the effect of reciprocating machine as a Water Hammer effect. It means that every time the pump increases the pressure you will have a FREE FORCE traveling along the pipe and acting in every elbow. This force will produce an additional movement and of course an additional stress and restraint reactions over supports.

I would recommend you to see Example 3 of the Application Guide.

Regards.

Nico.

Snubber - support or Snubber - vessel?

Regards,

Dear Nico/Dan,

what about the use of harmonic analysis module in Dynamic Analysis?

If we can use the following steps:
1. Modelling the pump foundation and crank as rigid and considering the Piston-cylinder as pipe(non rigid) in static module.
2. Putting the maximum pulsation force on each cylinder head points with some phase angles as obtained from vendor in the harmonic analysis module.
3. Specifying the frequency range for which we need to check the entire system.
4. Now assigning the stiffness for pump fundation, damper and crank in the harmonic analysis module.
5. Run the module with operating case.
6. The load cases as it appears

1Hz @ 45.01 phase.
2Hz @ 45.02 phase.......upto maximum frequency.

(My query 1Hz @ 45.01 phase is not matching with the phase angle I mentioned in step 2)

7. Now checking the entire piping layout in stresses and restraint loads in those frequencies load cases and adjust the supports to qualify stress.
8. Now incorporating these maximum restrain loads in the static model to do modal analysis and adjusting the frequency isolation by +-20%.

Does this procedure can be followed?
please give your valuable advice.

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