Expansion joint not functioning (Autopipe standard)

Hi, I've used a tied expansion bellow  on a 450 DN line in order to reduce the nozzle loads on a pump suction. However, it doesn't seem like its doing its job. I have specified the axial stiffness, weight and pressure area of the expansion bellow. According to the displacements, the expansion joint seems to be expanding longitudinally until the tie rod limit and creates a force around 60kN force on single tie-rod. Any ideas what could cause this? Thanks.

 

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  • Greetings, 

    Please add a screen shot of the Flexible joint dialog. What load case is causing the hig load on the Flexible joint? Be sure to list the operating condition, and then the individual load cases that make up said combination. One good question, is the analysis set containing the high operating condition have Pressure Extension Checked on?

    My initial guess is that it is a pressure load case. I look forward to seeing your updated information. 

    Regards,
    Mike Dattilio
    Design Analysis Engineering Group
    Senior Analyst Bentley Systems Inc
    =============================================================================

  • Hi Mike,

    Thanks for your response. The pressure extension is turned on and the pressure is 1000 kPa @ 45 degree celsius. The units are in SI. The 1000 kPa, 45 degree celsius load causes the high load.

    Regards,

    Ramith

  • Greetings, 

    I see that you have Axial stiffness set to non-rigid value. Therefore the joint is able to expand due to the pressure thrust of Pressure multiplied by Flex. joint Press Area or 1000 * 1500. This load will be restrained after the tie rods gaps closed. That is why you are seeing such a load on the tie rods. 

    I would suggest that you animate the operating conditions. If the movement does not appear to be correct, have a look at the Tie link gaps to be sure that they are configured correctly, see WIKI here

     Regards,
    Mike Dattilio
    Design Analysis Engineering Group
    Senior Analyst Bentley Systems Inc
    =============================================================================

Reply
  • Greetings, 

    I see that you have Axial stiffness set to non-rigid value. Therefore the joint is able to expand due to the pressure thrust of Pressure multiplied by Flex. joint Press Area or 1000 * 1500. This load will be restrained after the tie rods gaps closed. That is why you are seeing such a load on the tie rods. 

    I would suggest that you animate the operating conditions. If the movement does not appear to be correct, have a look at the Tie link gaps to be sure that they are configured correctly, see WIKI here

     Regards,
    Mike Dattilio
    Design Analysis Engineering Group
    Senior Analyst Bentley Systems Inc
    =============================================================================

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