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  • high accelerations causing excessive stress on rings around pressure vessel.

    Discussion in 'Industrial design' started by MSHOfficial, Jan 13, 2019.

    1. MSHOfficial

      MSHOfficial Well-Known Member EngineeringClicks Expert

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      Hello everyone,

      I have a pressurized container, that are held by 2 rings in place and a motor rotates it on its z-aixs. Since the material inside has very high viscocity. The material distribution during the rotation is not equal and this causes high stresses on the rings. Much higher than we expected initially. What are some ways we can reduce these stresses. Will rotating the cylinder slower make a difference? we would prefer to rotate it faster though. we cannot change the shape of the rings but we can add cushioning inbetween the ring and the vessel (because the ring is like a y shape, we can add small ball bearings thats might be able to transfer less stress to the rings, but we are not sure how it would turn out, if you guys have any experience regarding this please help). also if there are any other ways you guys could think about, I am open to suggestions.

      thanks in advance.
       
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    3. SenthilJPrakash

      SenthilJPrakash Member

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      A sketch or a picture would help us visualise the design and understand the issue.
       
    4. Mark_Armstrong

      Mark_Armstrong Member

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      I second the request for a sketch.

      That said, a slower speed should reduce the unbalance. Can you increase the speed slowly to allow the material to redistribute itself?
       
    5. Mark_Armstrong

      Mark_Armstrong Member

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      Is this an expeller? A centrifuge? Are you trying to separate the material?
       
    6. MSHOfficial

      MSHOfficial Well-Known Member EngineeringClicks Expert

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      upload_2019-1-20_16-46-29.png
      I understand you guys want to see a sketch but I dont have a sketch, but I tried my best to show you guys. so assume this is a symmetric cylinder and the whole thing is rotating around the center. The red circle is the disc that is the point of discussion here. the material inside is being mixed under 1,5 bar pressure. I dont have information about that except that the viscocity is around 22000 centipoise. the rotations start from 0 and reach 1500 rpm and at that speed the materials are somehow causing unequal stresses on the disc. The whole cylinder is supported at the disc by the way. its hanging basically throught the disc.
      upload_2019-1-20_17-1-38.png
      the attaching point is something like this. the rotating motor in attached on the top.
       
    7. Mark_Armstrong

      Mark_Armstrong Member

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      Interesting. Can you say anything about the application?

      That said, is the cylinder itself dynamically balanced? Any chance this is just dynamic in-balance in one or more parts of the cylinder?

      Also, if the cylinder is not concentric with the support ring, you will introduce forces there, I would think.
       
    8. MSHOfficial

      MSHOfficial Well-Known Member EngineeringClicks Expert

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      I don’t know about the application, I am just doing the design of the ring so I just have the required data from the guy who is giving me the job. But if I had to guess, maybe they are trying to mix concrete? I don’t know really. Or maybe it is a centrifuge to separate something under high pressure and accelerations.

      The cylinder without anything on the inside is dynamically balanced. It doesn’t give excessive forces until I introduce the pressure force and mass on the inside of the cylinder. The original design was to put a ball socket type joint on the top and bottom parts and then rotate from the side using a motor with rubber cushion. But that was introducing a lot of stress on the motor at times and the ball socket was not a good design, it would overheat due to the friction etc.

      Therefore, the team decided to build this and now they want to find the stress on the ring and the attachment point and that is my job. But they are stuck at this point, so I thought I would help them by asking this question here.

      The cylinder with the liquid or whatever inside causes extra stresses. Maybe they could use a doubler ring to make it stronger but its not a solution that I would prefer. Also I have restrictions on the ring dimensions and type of joint. And that’s another reason for not using a doubler.
       

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