CAEPIPE Frequently Asked Questions

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

Q-1. What is CAEPIPE?

A-1. CAEPIPE is the pioneering, premier software for performing linear and non-linear static and dynamic piping stress analyses. A piping engineer can check the piping system for compliance with a host of piping codes (ANSI, ASME, B31, International) and guidelines (NEMA, API). It contains its own geometric modeler with an analyzer. Results can be viewed and printed right within the software with interactive graphics (that includes the industry standard OpenGL (R)). Clear, formatted reports are the hallmark of CAEPIPE. For more details, please go to the software description page under CAEPIPE on the menu).

Q-2. Is your Evaluation copy (downloadable on this site) limited in features in any way?

A-2. We do not place any limitations in our Evaluation version. It is a full-feature, fully functional program. It is not time-limited like many other evaluation versions that have a 30/45/60 day expiration period nor is it crippled in any way (compare others where most analysis features are disabled and modeling is limited to 4"or 6" pipe or smaller). We provide a FREE copy with 20 data rows and ALL analysis features plus no limitation on pipe sizes. We encourage you to model any trial system and contact us for technical support.

Q-3. Printing problems

A-3. Sometimes the printing problem could be in data transmission from your computer to the printer. Please check to see 1. if your cables are ok, or 2. if there are printer settings that are incorrect, or 3. Check under Printer properties for incorrect settings, 4. Or some other setting in your system that may require a change (such as converting to a parallel transmission if you are using serial), etc.

Q-4. I connected a new printer. When I went to change the printer setting in CAEPIPE, I get a "Printer not found" message no matter which button I click on under the Print menu.

A-4. Caution: This operation, if done incorrectly, can disable your computer. Please exercise utmost care. Preferably, have your System Administrator do it. Note: When you do this, you will lose Caepipe settings (printer, options, preferences, window positions etc.). No model data will be lost or affected. Open the registry editor (Start menu, Run, regedit.exe). Search for the key "SST Systems". It should be expandable (that is, have a plus sign). When you expand it, you should see Caepipe. When you expand Caepipe, you shoud see Graphics Printer, Options, etc. Delete the key (SST Systems) on the left. Close editor and reboot system. Now, in CAEPIPE, attempt to change printer setting.

Q-5. Problems with Rendering the image in graphics window

A-5. Please try the following suggestions: 1. If you are using Win 9x, preview the OpenGL screen savers (pipes etc.) on your computer. This is usually available under Right click on desktop>Properties>Screen saver. If you can see the 3D OpenGL rendering of the screen saver then this will mean that OpenGL is enabled on your computer. If not, then please install those screen savers from your OS CD and then try CAEPIPE. 2. If you are using v5.02E, please upgrade to v5.02F. V5.02E supported graphics modes greater than 256-colors. Either you have to change the graphics mode to a higher color setting on your desktop, or use v5.02F. 3. The problem may have something to do with the computer hardware (specifically the graphics board). Try using another driver from Windows if you are using the graphics board supplier's driver, or vice-versa. Sometimes, the graphics acceleration hardware may interfere with rendering. Locate this feature in Graphics Display settings and disable it. 4. Delete the existing CAEPIPE installation. Install a new copy. Some files may be mixed up. 5. If the image is fuzzy in the rendered view, it could be happening because of very small dia. pipes you have in your model. Either increase the pipe size to see if this is the case or load the Sample model that is provided with CAEPIPE and render it to confirm. 6. Please load CAEPIPE on a different computer and see if it works there. 7. Please check your computer with the latest anti-virus software for viruses.

Q-6. While editing a model file I decided to take another look at the results to find them gone? Do I automatically lose a previous results file when I edit the model it was calculated from? If so, why? I don't want to have to print out each results. I can understand it being overwritten with a new analysis.

A-6. The moment you save a new revision to the model in input, the old results file immediately becomes invalid! Hence, the old results file is deleted to avoid confusion. Every model input file can be associated with one output file. The moment the input is changed and SAVED, the old results file is deleted. If you have to hold on to the old one, you will need to save the model to another name using "Save As" command under the File menu.

Q-7. Why don't the numbers under Sustained and Thermal add up to Operating load case results?

A-7. When a model has no non-linearities (such as rod hangers, friction, gaps, etc.), the forces/moments/displacements etc. will add up (i.e., Sustained +Thermal = Operating). When any non-linearity is present, each load case is solved independently, i.e., the numbers are not added, i.e., from Sustained (W+P) to Thermal (T1) to get (W+P+T1). Please look up pages 205 and 238 of [1]. In the past, this independent solution used to be the only method of solving when non-linearities were present. However, now we have a separate option (recommended) called "Thermal = Operating - Sustained" under Options menu > Analysis > Temperature. Use this option to solve for the thermal case as the difference between Operating and Sustained cases, which will also ensure that sustained and thermal cases add up to operating.

Q-8. Why does CAEPIPE not read older version results files?

A-8. CAEPIPE can read older version model files only. It is assumed that the model will be reanalyzed once it is converted to the new version (necessitated by inclusion of new features and/or bugfixes). Just as the existing results file is deleted once you save the model, same way, CAEPIPE deletes any existing older results file after conversion since it is the same as saving a model.

Q-9. Can two CAEPIPE models be combined?

Starting CAEPIPE v6.10, two or models can be merged. For those users who are using older versions and cannot upgrade, please follow the method outlined below.

A-9. Yes. It is possible to combine two or more models the "old fashioned" way! We are working on getting CAEPIPE to do it inside the program. The "old fashioned" method involves the following: 1. Export the model data from each model to a text file format (use File menu>Export). Say, we call this model1.mbf. Now generate model2.mbf. 2. In a text editor such as Notepad, bring in model1.mbf, copy contents, and now open model2.mbf. Paste the first file's copied contents below model2.mbf data. 3. Edit! Essentially, each file will have the same section headings. You need to keep the data under one heading, for every heading there is. You need to ensure that there is repetition (no repeating section, material, node number data etc.). 4. After you have the combined file, start CAEPIPE, use File menu>Import command to read the file in. For more information on format, please see Appendix C of the [1].

Q-10. What does the message "Unable to find plane for Branch SIF" mean? Program does not open the results file.

A-10. Closely examine your model. This message is generated when you have designated node(s) as a (Welding) Tee, whereas, physically, they are NOT tees (meaning less than three pipes meet at that node number). In B31.3 piping code, CAEPIPE needs three (3) nodes to find the in-plane and out-of-plane for further use. But less than three nodes are found. You need to replace these (Welding) tees with an equivalent User-SIF (this can be calculated from the guidelines given in App.D of the code book) and model should be reanalyzed. Or, add another pipe to make a complete tee.

Q-11. What does the message "Stiffness matrix not positive definite" mean? How can I correct it?

A-11. This message simply means that the piping model is incompletely restrained (model is "statically indeterminate"). The model has to be restrained properly in all six degrees of freedom (three translations and three rotations). For example, inputting a rigid Anchor at a node ought to fix this message. Or, a combination of all supports should collectively restrain the six degrees of freedom. This message could appear when model does not have the shear and the hoop moduli specified for the FRP material that you may have in your model. This message could appear when you have only one anchor in the model and you have released all 6 directions for hanger design. When they are released, there is nothing to support the model in these directions during hanger design. This is an unusual situation. Typically only vertical direction is released or there are other supports in the model. This message could also appear when you have jacketed piping in the model, and you don't have a Jacket Endcap at any node along the jacketed piping. A tricky situation could be when you have a component such as a valve that separates the jacketed piping into two and you don't have a Jacket endcap on one side.

Q-12. How is a bend modeled? How do I put a support on a bend?

A-12. A bend is modeled at the tangent intersection point (TIP). Note that this TIP is an imaginary point. It does not physically exist on the bend. As such, many users try in vain to put supports and hangers (Data types) at this node. CAEPIPE does not allow it since the node is an imaginary one. The user has two choices to put a support on a bend: 1. Create an intermediate node on the bend (open bend dialog box, and define intermediate nodes), or 2. Use bend end nodes (A and B nodes that are automatically defined by CAEPIPE after you define a bend). To input any Data type at a node, you have to use Location under Type (type L). So, to put a hanger at the bend end node 20B, you would do the following: On an empty row, (after the bend definition) a. Type 20B (or the intermediate node number) under Node, press TAB, b. Type L, c. Select Hanger (or any other Data type).

Q-13. Can I model a complete support structure in CAEPIPE?

A-13. Yes. You can model a complete support structure and connect that to the piping in the model. Use a Beam element to model the structure. CAEPIPE provides you hundreds of built-in AISC sections for your convenience.

Q-14. Can I model tied bellows?

A-14. Absolutely. There are simple and more involved methods. Please see two tips (for the months of Sep 1998, and Aug 2000) under "Tip for the month" link at our website.

Q-15. I have put in a cold spring, how come the stresses don't change?

A-15. Piping codes do not allow any credit for the stresses when a cold spring is put in. Only the support loads are affected. To look at the affected support loads, do the following: In Input, under Loads menu>Load cases, select all Cold Spring cases. Look at the appropriate load cases in results under Support Loads.

Q-16. How do I put in a cold spring? I don't see it listed as an element type.

A-16. Cold spring in CAEPIPE is input as a "Cut pipe" element. Input the length cut short or long. Look under Element types dialog for Cut Pipe.

Q-17. What is Xcomp, Ycomp, Zcomp in so many screens?

A-17. These are direction vectors (direction cosines). For example, if the vessel's axis was Y-vertical, you would put in Xcomp=0, Ycomp=1, Zcomp=0. For more examples, please see [1], page 145.

Q-18. How can I model the length of a flange?

A-18. The length of the flange has to modeled as a pipe (with additional stiffness, if deemed appropriate). In CAEPIPE, the length is usually not input because the flange is treated as a point property, i.e., it is input at a node, not between nodes. But, some "analytic types" want to be precise and they model the flange with an equivalent pipe section.

Q-19. Confusion between From in the first row and a repeat occurrence of From.

A-19. Every model in CAEPIPE begins from a "From" node. The meaning of "From" is simple: the piping model, or a branch or a new line starts at that point. In Sample.mod, From occurs twice, once at the beginning and next at start of a branch line from node 30.

Q-20. How can I change the friction coefficient for multiple guides/limit stops at a time?

A-20. Use the Edit>Change command to change at one time. Specify the starting and ending row numbers (NOT node numbers) and the new coefficient. All occurrences of the coefficient (in any data type that has it) within the row range will be changed to the new value.

Q-21. How does CAEPIPE select hangers?

A-21. Three step procedure: a. Calculate vertical reaction load (Lh) at all hanger locations by applying deadweight. Also called hot load iteration. b. Apply thermal load (T1 only, not T2/T3) and Lh for the preliminary operating load case. Note x, vertical thermal movements. c. Select hanger from catalog based on Lh and x. A more detailed explanation is given on page 178 of [1].