Optimization Wizard - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II Version
12

Piping Input menu: Model > Optimization Wizard

Wizards toolbar: Optimization Wizard

Assists with expansion loop design.

This wizard allows you to specify the element into which the loop should be incorporated, the loop type, the item to be optimized - nodal stress or restraint load, and the target value to which the item should be optimized. The optimization routines run the analysis several times to arrive at an acceptable loop size such that the code stress or restraint load on the target element is at the specified limit. Besides offering the opportunity to specify various loop configurations and a selection of height to width ratios, the wizard also provides an option to allow CAESAR II to select the most economical (based on length of pipe and number of bends) of those possible.

The Optimization Wizard automatically chooses the most economical loop solution based on your target input. If there is an issue with the target input or loop sizing, the wizard prompts you and attempts to insert the most ideal loop possible. However, you can always revise your target input or loop sizing and re-run the wizard.

To use the optimization wizard, the job must be run at least once so that there is an issue, such as an overstress, to resolve. These results must be current. The process is illustrated by the example LOOP-WIZARD.C2, as displayed below.

Reviewing the results of the LOOP-WIZARD job shows that it is suffering an expansion overstress of 46,741 psi. The allowable value at node 20 is 41,288 psi. This is due to the expansion of the long run 60-140. A loop should be installed somewhere along that run. The questions are where, and how big should it be?

Before you start the Loop Optimizer, examine the area of the plant surrounding the piping system. To do this, import the CADWorx (or AutoCAD) plant model, using the CADWorx Model command. In this case, import the ...\EXAMPLES\LOOP-WIZARD-PLANT\OVERALL.DWG model. This model shows that there is a convenient area to place a loop beside element 60-70.

Select element 60-70 and then click Model > Optimization Wizard start the Loop Optimization Wizard. The Loop Design Wizard dialog box displays.

Using the Loop Optimization Wizard:

  1. Loop 60-70 is already indicated as the element upon which the loop is installed. You can change this value by selecting a different value from the list, or by selecting other elements in the model.

  2. Click Stress as the optimization type. Optionally, you can optimize restraint load components as well.

  3. Select EXP from the Load Case list. This fills in the element list showing stresses on the left side of the dialog box.

  4. Type 36,000 in the Stress box to define a target maximum stress. This value refines the element list, so that it displays only those elements with stress levels higher than the target.

  5. Select the Max Stress box to limit the maximum stress in the system to the target value.

  6. Select the Loop Type from the available icons. For this example, select the first loop type.

  7. Select <none> from the Height to Width Ratio list to allow the loop height to vary to any size while keeping the width constant. In this case, the terminal run of pipe is set to one bend radius with the loop width fixed to the remaining length of element 60-70.

    At this point, there are two alternatives to indicating where the loop should be placed.

  8. Click Draw Cube to generate a transparent cube anchored on the selected element. You can adjust the size and location of this cube by using the mouse. Use the corner points (Pt1 or Pt2) to adjust the major direction of the loop and the available space. Use the triangle to adjust the minor axis of the loop and the available space. Drag the cube over the decking adjacent to element 60-70 to build a cube with a Major dimension of 17ft 11 inches in the –X direction.

  9. After the dialog box is complete, Click Design to start the optimization procedure.

    The progress of the design scheme displays. After the loop is designed, you are informed of how much pipe and how many bends were required to create the loop.

  10. Click Undo to restart the Loop Wizard using different loop types. You can use this information to find the most economical implementation.

    When the optimizer finishes, the new expansion loop is inserted into the selected element.

  11. Run a final analysis to verify all results. There are instances where the optimizer reports an error. Examples of such situations are: (a) requesting a loop insertion in an element that is not long enough, or (b) setting an impossible target maximum.

    Selecting the special loop type enables CAESAR II to select the best loop to reach the indicated target. This loop type is indicated on the dialog box by a lightning bolt. The best characteristic of each loop is based on the relative cost of bends to straight pipe. When you select the lightning bolt loop type, the Bend Cost Factor box activates. The default value of 100 indicates that a bend costs 100 times as much as the equivalent length of straight pipe. Adjust this value as necessary.