Spring Can Restraint Orientation on Skewed Pipe - CAESAR II - Reference Data

CAESAR II Applications Guide

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English
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CAESAR II
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Reference Data
CAESAR II Version
13

Pipe orientation may not always align with the global axes. The definition of restraints to account for friction must match the pipe orientation when using the Comprehensive method.

For the Simple method, spring cans do not need reorientation because the software does not create rigid elements.

Pipe Skewed in a Vertical Plane

When a pipe skews in the vertical plane, the pipe orientation lies between the vertical global axis and one of the horizontal global axes. The axial and lateral restraints orientations follow the global axis directions, projected onto the horizontal plane. Vertical restraint orientation follows the global vertical axis direction.

The software only considers a pipe skewed in the vertical plane if the angle is greater than 5º.

The software creates a rigid element from the pipe center to the pipe outer surface, oriented in the global vertical axis. You must reorient the element for the pipe orientation.

Before manual rotation of
the rigid element:

After manual rotation of
the rigid pipe radius element:

The Spring Can with Friction Builder creates the rigid elements shown by the dashed red lines in the below figure. The default orientation of the rigid elements matches the global vertical axis. To account for the skewed pipe orientation, you must rotate the rigid pipe outer radius element so that it connects to the outer pipe surface at a right angle. After rotation, the rigid elements align as shown by the solid blue lines.

Pipe Skewed in a Horizontal Plane

When a pipe skews in the horizontal plane, the orientation of axial and lateral restraints follows the local axis direction. Vertical restraint orientation follows the global vertical axis direction. The figure below shows the rigid elements created by the Spring Can with Friction Builder as dashed red lines. You do not need to reorient the elements.

Pipe Skewed in 3-Dimensional Space

When a pipe skews in both the horizontal and vertical planes, the pipe orientation lies between the vertical global axis and between the horizontal global axes. The axial and lateral restraints follow the element local axis directions, projected onto the horizontal plane. Vertical restraint orientation follows the global vertical axis direction. You must only reorient the element for the pipe orientation in the vertical plane, so the process is similar to that of a pipe skewed in a vertical plane.

The Spring Can with Friction Builder creates the rigid elements shown by the dashed red lines in the below figure. The default orientation of the rigid elements matches the global vertical axis. To account for the skewed pipe orientation, you must rotate the rigid pipe outer radius element so that it connects to the outer pipe surface at a right angle. After rotation the rigid elements align as shown by the solid blue lines.

Vertical Pipe

You can create a spring can for vertical pipe by two different methods.

Reorient the rigid elements

Create a comprehensive spring can at the vertical pipe centerline. The rigid elements created are in line with the vertical pipe centerline, as shown by the dashed red line in the below figure. Reorient the rigid elements between the SL and HN nodes to connect at a right angle to the outer pipe surface. The reoriented elements represent a horizontal trunnion connected to the vertical pipe, as shown by the solid blue lines in the below figure.

Place the spring can at a horizontal trunnion

Create a horizontal pipe element connected to the vertical pipe to act as a trunnion. Create a comprehensive spring can at the horizontal trunnion centerline, as shown by the dashed red lines in the below figure.