Thanks for the reply. I guess im not actually looking to calculate the stiffness of the piping system. We had a company come out and do a vibration analysis on out compressed CO2 lines and they identified a few areas of high shaking force. The fource they determined to be around 400 lbf. Im trying to figure out for our relibality engineer if 400 lbf is significant. API 618 isnt all that clear on acceptable limits and so forth. The funny thing is that I know nothing about structural engineering as I am a chemical engineer rite out of school. God I love work!
You need a static and dynamic stress check on the pipe (maybe including the supports too) that includes an evaluation of the cyclic fatigue implictions of that vibration. You don't calculate the stiffness of the system for that, unless you have a lot of time with nothing to do. Better to spend that time learning something about pipe stress analysis and to get proficient in a good stress analysis program. Or better yet, higher a consultant to do this analysis this time and learn from him how he did it.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
1) Was the analysis done to API 618 4th edition or 5th? There are substantial changes in the evaluation of shaking forces.
2) If high shaking forces were identified, were recomendations made to absolve them? This should take the form of oriface plates in specific locations, addition of pulsation bottles, changes to the size of bottles, addition of bottle internals, ect.
3) The shaking forces come about due to resonance in the piping due to a pulsating compresible media. These pulations occur at the operating frequency of the equipment or multiples thereof, a 400 pound fouce at a high frequency can be a real conern, or not it depends on your system.
4) Due to the nature of the excitation, the stiffness of the system will not effect the presence of the force. i.e. additional stiffness or more flexibilty will not remove the forces, thus the reason for recomendations to mitigate the forces focus of quiteing the excitations rather then changing supports.
