Time Force profile

Posted by: Van Ha

Time Force profile - 03/14/18 12:31 PM

I have sistuation that there are vibration lines at site due to slug flow. It requires to solve the vibration issue. There are two options I think I can do

Option 1:
Do the static analysis with estimate slug force (DLF=2) to modify appropriate supports. The lines have never been analyzed before and existing support conditions seem not good (less guide and no stopper). This option like a new design.

Option 2:
Do the dynamic analysis (time history). But I need Time vs. Force profile. What kind of data should request from site? After that, any hydraulic transient analysis required to generate Time Force profile or how I can estimate by hand from site data?
Posted by: Michael_Fletcher

Re: Time Force profile - 03/14/18 02:38 PM

As usual, "it depends."

If you have predictable pipe reactions (i.e. slug frequency << natural frequency), then you'd request measurements of the displacements as well as the frequency at which they occur. Once you have this info, you can back out slug loads.

If your pipe is moving unpredictably, that means your slug frequency is near or greater than the piping natural frequency, and you may not be able to be supplied reliable information by which to form an analysis.

There is no good way to predict what the inputs of a system are based on erratic unpredictable outputs of the system. Perhaps you can get lucky and come to a reasonable approximation if you have displacement data through trial and error. However, my opinion is that if they have erratic vibrations, you should be supplying them information on how to improve the system from "bad and unknown" to "maybe bad but known, but definitely not making things worse." Once they stiffen up the system, you can then evaluate whether the new configuration is adequate.