3 Replies Latest reply on Sep 25, 2018 10:51 AM by Jim Roberts

    Bourdon Tube Testing - Simulation setup

    Jim Roberts

      Looking to run a simulation on a pigtail Bourdon tube.  I have the tube, spiraled it, added a cap, and now I want to run the simulation.  I have run it a few times, but I am unsure the results are what I want because I am not sure I have set it up properly.  Also, I would like to see how 15,000 psi would move the unit, but when I run the simulation it does not move.  The Bourdon tube should uncurl as it pressure goes into it.  How do I set this up and is there anything out there I can watch/read about to show me how to do this?  I work for a Gauge distributor and we are getting into manufacturing and I will have to do several simulations on both spiral and C shaped Bourdon tubes. 

       

      For those that are unfamiliar with Bourdon tubes here is a simple video

      WHAT MAKES IT WORK? #15 How a Pressure Gauge Works tubalcain bourdon tube - YouTube

       

        • Re: Bourdon Tube Testing - Simulation setup
          Bill McEachern

          You probably need a non linear simulation for this to get good accuracy. If you are attempting the whole mechanism you would definitely need an NL solution. That said though it should be reasonably attainable but it may have some challenges. Just doing the tube itself should be pretty straight forward. I don't download things so better to post images of what you have and i would be happy to comment.

          • Re: Bourdon Tube Testing - Simulation setup
            Ryan Navarro

            Hi Jim,

             

            I have two concerns based on your setup:

             

            1) I noticed your model has a circular cross-section

             

            From the limited searching I did it seems Bourdon tubes rely on a non-circular cross section for their effect. Wikipedia states "The Bourdon pressure gauge uses the principle that a flattened tube tends to straighten or regain its circular form in cross-section when pressurized...."

             

            So it would seem a non-circular (oval or "flattened") cross section is crucial to capturing the behavior. Forgive me if I'm off base here

             

            2) This is a geometrically nonlinear problem

             

            I noticed you have the study set up to run in Large Displacement mode, which is the best option available in a Static analysis.

             

            Do you have access to Nonlinear analysis study type? There's an option that can be enabled in the Solver properties to "Update load direction with deformation". Without this option enabled, the force/pressure directions do not change as the part deforms. This is pretty much required for pressurization problems with large scale deformation (such as inflating a balloon or membrane) Since the deformations are probably more subtle here I am not sure if it will be required, but it is a good thing to know about

             

            I would try to verify if the cross-section of the tube is correct, and then also look into see if you have access to the Nonlinear study type (requires Simulation Premium)

              • Re: Bourdon Tube Testing - Simulation setup
                Jim Roberts

                Ryan, you are correct, the tube will be a flattened circle (they begin as a tube then get rolled and they flatten).  I have it designed as an ellipse with the current model having height and width equal.  I guess this leads to another question, do I have this designed right if I elongate the width or do I need to make it more of a slot shape?  We know what the OD will be of the circle before being flattened but we are getting tripped up on how to make the formula correct to appropriately size the "crushed" tube.  Looks like I do not have non linear simulation, so I will talk with my local distributor and see what will go into purchasing this as I foresee running similar simulations often as we begin to go into our own Bourdon tube designs.  Thank you for responses Ryan and Bill.  I apologize for my "green-ness" in the world of simulation.