Estimate offshore pipe wall thicknesses - CAESAR II - Help

The DNV Wall Thickness Calculator, combined with CAESAR II piping analysis, lets you estimate the necessary wall thicknesses along an offshore pipeline, based on pipeline depth, pressure conditions, and DNVGL-ST-F101 standards.

Different locations along the pipeline may use different thicknesses based on water depth and material cost. At each of these transition points, use the DNV Wall Thickness Calculator to estimate a new, required thickness.

Set up the model

1. Click Home > Input > Piping Input in the CAESAR II main window and design the pipeline model in the Classic Piping Input dialog box.

2. Assign DNV 2017 as the Code and assign Allowable Stress information.

3. Click Start Run to run error checking. Correct any errors found by the software.

4. Click Edit Static Load Cases .

   The Static Analysis - Load Case Editor window displays.

5. Create your needed load cases and wave loads.

   

   • Use the LMST stress type for combination load cases.

   • You can import example load cases for empty, water-filled installation, operation, and hydrotest conditions. The software includes DNV Recommended Load Cases.xlsx in the C:\ProgramData\Intergraph CAS\CAESAR II\<version number>\System folder. Use Import Excel File in the Static Analysis - Load Case Editor dialog box.

6. Click Save and Cancel to return to Classic Piping Input.

7. Determine element locations along the pipeline to use for estimating wall thicknesses.

Run the DNV Wall Thickness Calculator

1. Select the first element with DNV parameters, and then click DNV Wall Thickness Calculator .

   1. Define global settings for the pipeline on the Global tab.

   2. Review piping input and allowable stress properties on the Geometry tab and the Material tab.

   3. Define pressure cases on the Reference Data tab, burst and buckling details on the Design tab, and load interaction details on the Load Interaction tab.

   4. Review results on the right side of the calculator window. Find the results that indicate the recommended maximum required wall thickness (treq) to use for the pipeline element.

      The results automatically update as you add and change values.

   5. Click Update.-8 0v

      The software displays a message asking if you want to transfer the maximum wall thickness to the piping input.

   6. Click Yes to change the selected element wall thickness in the model.

      The DNV Wall Thickness Calculator closes.

      The software changes the value of Wt/Sch in Classic Piping Input to the maximum value of treq in the calculator.

      

      • Check the value of Depth of Pint in Pipe on the Design tab. It must match the depth defined by the node coordinates on the Coordinates list in Classic Piping Input.

      • The wall thickness is a calculated value that may not match a commercial pipe size. In that case, round up the thickness to the next commercial pipe size.

2. Repeat step 1 for each of the remaining elements to estimate, changing wall thickness as required due to water depth and material cost

Analyze the model with calculator results

1. In Classic Piping Input, click Batch Run to check for errors and analyze the model.

   When the analysis completes, the Static Output Processor window displays.

2. Create the following reports:

   • DNV Thickness Overview for design wall thicknesses.

   • DNV Components for minimum thickness and utility values.

   • DNV Details for forces and moments.

3. On the DNV Components report, review the minimum thickness and utility values.

   • If all utility values are less than 1.0, the thickness values are acceptable, and no refinement of the model is needed.

   • If a utility value is 1.0 or greater, you must refine the model and continue with the procedure below.

If a utility value is 1.0 or greater, re-run the calculator and analysis to refine the model

1. Close Static Output Processor and return to Classic Piping Input.

2. For each element, click DNV Wall Thickness Calculator .

   1. Add forces and moments from the DNV Details report to the Load Interaction tab.

   2. Observe how the new forces and moments affected the required wall thickness (treq) calculations. If treq calculation results changed from the previous results, click Update to re-apply the maximum treq value to Wt/Sch in Classic Piping Input.

   Do not change values on the Global tab. Changing global values invalidates previous results. You must re-run the calculator again on previously calculated elements.

3. Click Batch Run to check for errors and re-analyze the model with the new wall thicknesses.

4. Recreate the DNV Components report and check that all utility values are less than 1.0.