Introduction to Pipe Support


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2 Responses


    Valery, the man built the plants before the creation of finite elements theory. Codes have been developed to rule these issues. We are engineers, not physicists. A simplified theory with a safety margin is better than a precise but too time-consuming one. A theory based on experience results is also acceptable even if not supported by theoretical calculations in its entirety. So We have code by rules (B31.etc) that are not “illegal” and also supports standard that have been always used and only now analyzed with the new calculation methods. So We can consider a Pipe as a Beam, the important is to know when a shell problem can arise, but codes help to avoid them.

  2. The application of the theory of girder finite elements to the stress simulations of pipelines is “illegal”.

    The hypothesis of FLAT sections and the Saint-Venant principle are valid only for long rods of a LIMITED profile, i.e. having transverse dimensions of ONE order!

    For thin-walled beams, when one transverse dimension is much larger than the other, estimates of the relative orders of magnitude of the normal and tangential stresses cease to be valid, the hypothesis of flat sections loses force and the Saint Venant principle becomes unacceptable.

    Pipe is not a beam element

    Pipe is a thin cylindrical shell

    Therefore, for almost all cases – the pipeline should be considered as a shell construction

    In the process of loading the pipeline, the cross section ceases to be perfectly round – the curvature of the pipeline changes, both radially and in the longitudinal direction – this can not be taken into account by the theory of beam finite elements.

    The beam theory of finite elements excludes the possibility of REAL simulation of the contact of pipelines with supports.
    And since in the process of loading the area of contacts and their location change – the beam theory of finite elements can not give REAL values of stresses that arise in contacts.

    You are mistaken in saying that the pipelines have small deformations.
    Almost always – pipelines have large deformations and almost always pipelines have geometric nonlinearity.

    Applying the theory of beam finite elements it is impossible to obtain distribution of stress at the intersection / conjugation of pipes, as well as at the intersection / junction of pipes with reservoirs.

    Applying the theory of beam finite elements it is impossible to correctly define the boundary conditions that simulate the supports – since the boundary conditions are set to points located on the axis of symmetry of the pipeline.

    In fact, the support of the pipeline to the supports occurs along the outer surface of the pipeline – thus the “error” in setting the boundary conditions will be 0.5 the radius of the pipeline.

    The consequence of this is an incorrect calculation of the forces , bending and twisting moments => incorrect distribution of strain/stress in pipe.