Load on Pipe Support

Hi,

I am doing an assignment on a process loop in which a centrifugal pump is pumping water through a long spool into a process tower (height = 50 m). During an earthquake, the liquid line towards the process tower showed excessive vibration. The entire spool has supports installed. My assignment is to analyse the spool in AutoPIPE to find whether the installed supports are sufficient or not and properly located or not.

I have a few queries:

1) How can I add pump vibration to the spool without actually modeling the pump? Is there a way to impose those vibrations on the pump discharge nozzle in the piping model?

2) While inserting supports, AutoPIPE asks about the gaps. If I run a static analysis, the displacement on these supports comes out to be more than that gap. For example, if I specify a gap of 3 mm left and right, displacements up to 6 or 7 mm are observed at some supports. Whereas the stress analysis shows no zone with stress ratio higher than 1. Is it OK or does this mean that the support has failed?

Please help.

  • Hello Bilal,

    With regards to your questions:

    1) How can I add pump vibration to the spool without actually modeling the pump? Is there a way to impose those vibrations on the pump discharge nozzle in the piping model?

    Answer: AutoPIPE is able to run different types of dynamic analysis:

    • Modal Analysis
    • Response Spectrum Analysis
    • Harmonic Analysis
    • Time History Analysis
    • Force Spectrum Analysis

    You would use the Harmonic Analysis feature to model your pump vibrations on the piping system.

    2) While inserting supports, AutoPIPE asks about the gaps. If I run a static analysis, the displacement on these supports comes out to be more than that gap. For example, if I specify a gap of 3 mm left and right, displacements up to 6 or 7 mm are observed at some supports. Whereas the stress analysis shows no zone with stress ratio higher than 1. Is it OK or does this mean that the support has failed?

    Answer: The WIKI pages answers a lot of questions such as this, please review the following WIKI page here, see item #6. 

    Regards,

    Mike Dattilio

    Bentley Product Advantage Group Analyst

    AutoPIPE Product Line Bentley Systems, Inc.

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  • Thanks alot sir. But in my case, even then GR+T1+E1 cases are exceeding gap limits at some points. Not at supports but between 2 supports, this load case is giving higher displacements. Is that normal ?
  • Hello Bilal,

    Absolutely, the amount of displacement not at a support point can be any value. However at a support pipe movement is restrained based on support settings (i.e. Gaps, Friction, Connect to point, Support Stiffness, etc..).

    Again, pipe movement is free outside of support locations.

    Regards,

    Mike Dattilio
    Bentley Product Advantage Group Analyst
    AutoPIPE Product Line Bentley Systems, Inc.

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