Version Usage Tips Volume 3

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Hydrotest Pressure Feature

CAESAR II users can specify a value for the system hydrotest pressure. The entry for this pressure can be found at the bottom of the piping input spreadsheet, just below P1 and P2. Additionally, an entry field for this pressure also exists on the extended operating conditions dialog. Both of these hydrotest pressure fields are shown in the figure below.

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When a hydrotest pressure is specified, CAESAR II will recommend a load case consisting of WW + HP. The components in this load case are:

  • WW: Pipe weight filled with water. This includes insulation and/or refractory if specified.
  • HP: The specified hydrotest pressure.

For this load case, it is assumed any spring hangers are locked against movement. A typical set of load cases, including a hydrotest case, is shown in the figure below. Note that "Case 1" is the hydrotest case.

Click to enlarge.

Graphics - Displacements & Forces

The 3D Graphics engine can display applied displacements and forces in tabular format. The display windows can be scrolled vertically to review all node points where this data has been defined, as well as horizontally to review all nine possible load vectors. The color key at the far left of the window assists in locating the node points on the model (when the model geometry is complex). An example showing the applied displacements in a model is shown in the figure below.

Click to enlarge.

Note that the displacement window also indicates free Degrees of Freedom (DOF). In this case, a free DOF is a DOF where no displacement value has been specified. Note also that if a certain DOF has a specified displacement in one of the nine possible load vectors, then it si fixed in all other load vectors.

Printing Input for Verification

In many instances, it is desireable to print the piping model input in columnar style to aid in model verification. This can be easily accomplished using the CAESAR II LIST Processor. The initial windows displayed in this LIST processor is shown in the figure below.

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To prepare for printing, any unnecessary columns can be collapsed, by using the mouse and sliding the grid lines together. Next, turn off the display of duplicated data. The resulting display is shown in the figure below.

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Finally, print this information in Landscape orientation. A Print Preview of this setup is shown in the figure below.

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Load Case Options

One of the most important task of the stress analyst is to properly define the load cases necessary for a proper system evaluation. CAESAR II not only makes load case definition easy, but it also provides a comprehensive set of options for combining load cases and evaluating alternate system conditions. The load case edting dialog is shown in the figure below.

Click to enlarge.

In this figure, region 1 lists all of the primative loads that have been defined in the input, and are therefore available for use in load cases. Region 2 is the actual load case area. Each line in this region represents a load case. Load cases are either basic cases (composed of primative loads) or combination cases (composed of combinations of previously defined load cases). Note that each load case has a stress identifier to the right of the load case definition. This control is actually a "drop list" providing a selection for the type of load case (which governs which code stress equations are used).

Region 3 provides controls to have CAESAR II recommend load cases and to provide additional input fields to define the number of times a load case may cycle (for fatigue analysis).

Region 4 consists of a set of tabs to control what is displayed in the dialog box. These tabs provide: additional load case options, data fields for up to four wind vectors, and data fields for up to four wave vectors.

Region 5 contains a set of controls to: add or remove lines from the load case area (region 2), save the load case setup, and perform the analysis.

Load cases can be constructed by using the "plus" key in the toolbar to add lines in region 2. Primative loads from region 1 can be dragged into region 2, or typed in. Once the necessary load cases have been defined the tabs in region 4 can be used to define the specifics regarding wind and wave vectors.

The second tab of region 4, Load Case Options provides a number of very powerful capabilities. Users are urged to study the options available here. The Load Case Options tab is shown in the figure below.

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Notice that in the Load Case Name column, meaningfull names have been used to replace the standard CAESAR II load cases. These names can be optionally used in output reports if desired. The use of these "user-defined load case names" makes interpreting output reports much easier, especially when a large number of combination cases have been defined.

The Output Status column is used to eliminate load cases from possible output review. This is useful when load cases are defined as construction or component load cases only. Additionally, spring hanger design load cases are usually have their status set to Discard since the results of these load cases are typically not of interest to the analyst. This column will display a drop list, when clicked on the right-hand side.

The Output Type column is another column used to reduce output. By using the drop list available here, users can select which type of output will be available on a "load case by load case" basis. Notice in the figure above, the first two cases will only provide displacements and forces, cases three and four will provide displacements, forces, and stresses, and case five will only provide stresses.

The Combination Method column is particularly useful. This column provides advanced combination methods, as shown in the figure below.

Click to enlarge.

Details on these combination methods can be obtained by clicking on this column, and then pressing [F1] for help. Note that the Max and Min options can be used to summarize a large number of load cases.

The Snubbers Active? column can be used to activate snubbers in any desired load case, not just occasional load cases.

The Hanger Stiffness column can be used to dictate how spring hangers are treated on a "load case by load case" basis. Available options here are "rigid," "as designed," and "ignore." Details of these settings can be obtained from the online help system by pressing [F1].

The Friction Multiplier column can be used to alter the effects of friction on a "load case by load case" basis. By default the multiplier is set to 1.0, which means that the load case will use the coefficient defined in the input. Changing this multiplier to another value means that the coefficient of fricion defined at the restraints will be multiplied by the specified value. For example, if the coefficient of friction at a particular restraint was defined as 0.3, then a multiplier of 1.3333 will case the analysis to use a coefficient of friction at this restraint of 0.4.

3D (HOOPS) Element Viewer

One of the best features of the DOS versions of CAESAR II was the Element Viewer. This capability allowed sequential review of each element's data, in a graphical view. The data displayed included the node numbers, the displacements, the forces, and the stresses.

A new viewer has been added to the Windows version using the 3D HOOPS engine. This new viewer is shown in the figure below.

Click to enlarge.

This viewer provides a moveable, scrollable window which allows review of all of the system's nodes, and all degrees of freedom The tree structure to the left allows selection of load cases and the type of data to be displayed.

Note that the current element is highlighted in both the viewer window and on the model graphic. Clicking on a different element on the graphic will move the viewer window to the corresponding element. Similarly, clicking on an element in the viewer window will highlight the corresponding element on the model graphic.
© Copyright 2012 Intergraph Corporation - Printed from on 10/20/2016 7:20:39 PM