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CAEPIPE Frequently Asked Questions Part 2

Reference [1]: CAEPIPE User's Manual, v5.1J, 2003.

Q-22. Can I use the Limit stop to model a no gap vertical one way support (like for a pipe rack)?

A-22. Yes. The limit stop can be used to model a 1-way support. Leave Upper limit blank, enter 0.0 for lower limit, and you have it. CAEPIPE's default direction is vertical (Ycomp=1).

Q-23. The program won't allow me to go to T2, P2, T3, P3 fields. How do I get there?

A-23. In Input, under Options>Analysis>Tempertaure, select 2 or 3 for Number fo Thermal Loads.

Q-24. Can I add my own material to a library?

A-24. Yes, select File>New...Material Library. Open the material library of your choice (or start typing data and save later as a new material library file), and add new materials.

Q-25. How to model a miter that has 5 or more cuts?

A-25. Based on the method outlined on pages 232-234 of [1], you will have to create your own. If you do, please send us the completed drawing and we will include it in a future version.

Q-26. What are internal nodes? Can I specify any alphabetic letter to the end of a node number?

A-26. Unfortunately, you cannot specify an alphanumeric node number in CAEPIPE except in a few cases such as Jacket, bend, jacketed bend. These types automatically create alphanumeric nodes (internal) and CAEPIPE allows you to input additional Data for them.

Q-27. Should I use a nozzle in CAEPIPE? Can't I use an anchor instead?

A-27. Yes. You can use an Anchor instead of a nozzle. Keep in mind the different coordinate system for the nozzle when you view results. Answers could be conservative when you use an anchor instead of a nozzle.

Q-28. How do I get API 610/617, NEMA-SM23 reports?

A-28. When you have a line that ends at a rotating equipment, input one under the Misc. menu. On analysis, you will be presented a Rotating Equipment Report.

Q-29. How to model an eccentric reducer?

A-29. See example on page 250 of [1]. Use a regular Reducer type. At the To node, merely specify the eccentricity as an offset on the layout screen (DX or DY or DZ).

Q-30. Is the Restraint in CAEPIPE a 1-way restraint?

A-30. No. An X or Y or Z Restaint is a 2-way rigid restraint. To model a 1-way rigid restraint, use a Limit stop with Lower limit = 0.0, and Upper limit=(Blank).

Q-31. How can I add lining to the pipe?

A-31. Under Misc. menu>Sections>Dialog box (press Enter when you reach here), look for a field called Lining and Lining Thickness.

Q-32. Where do I use a User hanger type?

A-32. Where you have a hanger in the field that you want to model in CAEPIPE (as opposed to a hanger you want to be designed). You can input as much data for the hanger as you have access to. CAEPIPE calculates the rest.

Q-33. What is the use of User-SIF? How does CAEPIPE calculate SIFs?

A-33. CAEPIPE allows users to override the internally calculated SIF by using the Data type "User SIF." CAEPIPE has all codes' SIF calculation methods built-in. See Appendix D under piping codes section (appendix A of [1]).

Q-34. Can I model a globe, angle, relief, butterfly, etc. valve?

A-34. In CAEPIPE, the important properties in a valve are the items it asks you in the dialog box. Differentiation is not made when it comes to the different types of valves. It would have more meaning in a design program.

Q-35. Can I find out the total weight of the model?

A-35. Yes. By adding up all the vertical direction loads for the Sustained case (W+P). In CAEPIPE version 4.1 and earlier, in Results, select Misc. menu>Center of Gravity command. This will be reinstated in a future v5.x release.

Q-36. How do I turn off in graphics all node numbers displayed at the same time?

A-36. In the graphics window, right click anywhere, select Show> (uncheck) Node numbers.

Q-37. How to model "bottomed out" springs?

A-37. Use a combination of a Limit stop with a spring hanger. The maximum travel at the hanger needs to be input as one of the limits at the limit stop. The hanger , after traveling the limit will see the stop.

Q-38. What is SL, SE, SO etc.? Where can I find information on it?

A-38. These are all piping code related terminology. Please see appendix A of [1] under each piping code for an explanation. The best answers can be got from a study of the piping code itself.

Q-39. Under Results>Pipe element forces, how come the same node (eg. 20A) appears on two rows and has different forces/stresses?

A-39. Any A or B node designates a Bend element. CAEPIPE splits the elements into, 1. Upto the bend starting node (e.g., 10-20A), 2. the bend itself (20A-20B), and 3. from the bend ending node (20B-30) to the next one. So, you will see a repeat of the node numbers. Since the node numbers become part of different elements, the answers may differ.

Q-40. In the code compliance screen, what are the two numbers in the third column (Press., Allow.)?

A-40. These are the Internal (user input) Pressure and the piping code calculated Allowable Pressure. The equation for Allowable pressure may be found under the appropriate piping code in Appendix A of [1].

Q-41. What is cold load and hot load (in reference to hanger design)?

A-41. Hot load is the load that balances the piping system under the sustained loads. Cold load is calculated as hot load + (spring rate * hanger travel). See page 179 of [1].

Q-42. Valve forces/moments are not listed!? Where are they?

A-42. Valves are listed under Element forces in the Results list. Pick "Other forces" under the Results menu. So also are rigid elements and other non-pipe elements.

Q-43. What is hot allowable stress?

A-43. It is the "basic material allowable stress at the Design Temperature" (ASME SIII, NC, 1992, p 174). See Material properties in CAEPIPE for the correct value. CAEPIPE will interpolate linearly if required, for the allowable stress value.

Q-44. Explain the options given in the Options menu.

A-44. Please see the Section titled Input and Output menus in the User manual supplement. It can be downloaded from our website. Select FREE Evaluation copies at, fill in the form, click on Download and proceed to the Download page. The file to download is titled "CAEPIPE v5.02x User manual Supplement." It is an MS-Word document.

Q-45. What is the local coordinate system (LCS)?

A-45. It is the coordinate system for each element in the model. For a straight element (such as a pipe), the local x axis is along the element (from the "From" node to the "To" node). For a node location (such as a guide), the local axes are based on the previous connected element; if not available, then on the next connected element. The local y and z axes are calculated depending on whether vertical direction is Y or Z and whether the element is in the vertical direction.

LCS is different from the global coordinate system that is shown by the Axes symbol in the Graphics window. It can be shown graphically for most elements in Results under Element forces. Select "Show LCS" under the View menu in Results, and move highlight to each element. Please see p.214 of [1].

Q-46. Are anchor releases important and if so, how do I release them?

A-46. Anchor releases are usually confused with having no restraint in that direction. Anchor releases are important only during hanger design. The purpose of such is to ensure that the loads are taken by the hangers nearby equipment. CAEPIPE automatically restores the releases after hanger design. Please see Anchor, pages 91 - 92 of [1].

Q-47. How do I model a relief valve force as an occasional load?

A-47. Please see Tip for the month of January 1999 (on our website) for a detailed explanation of the procedure. A near future version will have this procedure automated in CAEPIPE.

Q-48. What are in-plane and out-of-plane moments and SIFs?

A-48. Certain piping codes such as B31.3 have two moments at changes in direction (at an elbow, for example). The moments in the plane of the elbow (two elbow end nodes with the center define the plane) are called in-plane and those outside of it are out-of-plane. Similarly with SIFs. Please see section 319.4.4 of B31.3 for more information.

Q-49. Why is the force in the operating load case zero at a rod hanger?

A-49. Zero force means at the hanger means it is lifting up in the operating load case. Note that in CAEPIPE, the redistributed weight in the system, because of a support lifting up, is not used to recompute the Sustained stresses. The stresses are from the as-installed cold condition. For the rod hanger, you may want to check the other load cases' results (such as Sustained and Thermal) to determine the design loads.

Q-50. Where can I find "Support design loads" in a CAEPIPE report?

A-50. The support design loads (at various supports) need to be determined by looking at all loads for each load case. The design loads would be the absolute maximum amongst all loadcases. In case of the rod hanger where there are zero forces, you would look at Sustained and Expansion (plus/minus seismic) and take the worst case. In cases where you have a seismic load case, you (manually) need to add and subtract the seismic results from the Operating load case results to get the range and take the absolute maximum as the design load.