HELP Needed - Issues

This forum contains general questions about pipe stress, not necessarily related to ROHR2
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Mechanical Engineer
Beiträge: 8
Registriert: Di 8. Nov 2016, 09:17

HELP Needed - Issues

Beitrag von Mechanical Engineer » Fr 6. Jan 2017, 18:08

Dear all,
I Have started evaluating ROHR2 32.0 software. I considered training materials 01 and 02. For my work, I need to analyze pipe movement and stress analysis due to thermal expansion and other forces imposed on iping system.
I built my own model. I would kindly ask for further clarifications...

1) Please advise if dead load analysis consider weight forces only (pipe+medium+insulation) WITHOUT thermal expansion.
2) How to add HVAC elements e.g. tanks, air handling units and connect them to piping system? On the web site, I see some examples where tanks are connected to piping system. As I was not able to do this, I used approach in which connection point between piping and air handling unit are presented as fixed anchor.
3) What is difference between calculation and operational data? Operational data are used by software algorithm for analysis, correct?
4) I encountered several problems with T fitting and reducers. I was not able to add T fitting and got error message "Wrong number of couplings". What is correct way to add T fitting?
5) Whats is difference between head vs blind flange? When I added head, I was expecting to see Header (pipe manifold) but did not.
6) What is presented by point mass?
7) Please take a look of attached error report and my model. Please advise how to correct them and make change distances between nodes that are touching each other.
I think that mistake occurred when I was trying to add reducers, Tees and change pipe dimensions. For example, I drew pipeline layout using the same diameter e.g. DN80. Then I started adding reducers e.g. DN100toDN80, DN250 to DN200 etc and changing pipe dimensions. Moreover, I could not add Tees when have 2 different pipe sizes for branch and main run. I used approach to drew main runs first and added branches and changed pipe size later. Finally, I noticed that software does not recognize Tees, bends reducers. In attached model file, you will notice that in list of components for fittings there is 0. Please advise on the best approach to drew pipeline network with Tees, reducers, bends.

8) What is axial stop in support type? Please provide an example.
9) What operation data to use for Shutdown option? When does this situation occur?

Your prompt reply would be greatly appreciated.
Thank you.
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Zuletzt geändert von Mechanical Engineer am Fr 13. Jan 2017, 15:02, insgesamt 1-mal geändert.

Mechanical Engineer
Beiträge: 8
Registriert: Di 8. Nov 2016, 09:17

Re: HELP Needed - Issues

Beitrag von Mechanical Engineer » Mo 9. Jan 2017, 13:07

Hello,
Please find attached error report for a second simulation (Model 2). Please advise on how to correct them.
Thank you.
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Mechanical Engineer
Beiträge: 8
Registriert: Di 8. Nov 2016, 09:17

Re: HELP Needed - Issues

Beitrag von Mechanical Engineer » Fr 13. Jan 2017, 11:30

Dear ROHR2 technical supportm

Please advise
(1) on difference among dead load (S1-01), range (S3-02) and dead load, range (S4-03) in stress analysis results?
In other words, does S1-01 consider forces imposed on system due to weight only excluding effect of thermal dilatation?
Similarly, does S3-02 consider only forces imposed on system due to thermal dilatation only?
Does, S4-03 consider combined effect of dead load and range simultaneously?
Which stress analysis should be used for analyzing problems with hot water piping S3-02 or S4-03?

(2) What is range? How this relates to operation scenario?

(3) How to include Stress Analysis S4-03 in report only? From Documentation/Create report , the software generates report with S1-01 Stress Analysis (Dead Load). Only when Appendix is selected, S4-03 is included in Appendix.

Thank you
Zuletzt geändert von Mechanical Engineer am Fr 13. Jan 2017, 15:02, insgesamt 1-mal geändert.

Mechanical Engineer
Beiträge: 8
Registriert: Di 8. Nov 2016, 09:17

Re: HELP Needed - Issues

Beitrag von Mechanical Engineer » Fr 13. Jan 2017, 14:16

Dear ROHR2 Support,
Could you reply to my concerns as I am using trial version of your software to evaluate its functionality,please .
Much appreciated.

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rohr2admin
Administrator
Beiträge: 417
Registriert: Di 13. Sep 2011, 14:03

Re: HELP Needed - Issues

Beitrag von rohr2admin » Fr 13. Jan 2017, 15:47

Dear user,

Maybe it would be helpful for you to have a look at our webpage under the section “service” and “download” section, where we collected some material which shows the workflow of ROHR2:
http://www.rohr2.com/en/downloads.html
Regarding your questions:
1) This load case is the according primary load case (weight of pipe, insulation and media + pressure) for your secondary load case (thermal expansion). Due to this you have to enter the operating conditions, pressure and temperature as well.
2) You can either use rigid elements or pipe sections with the acc. diameter to represent the equipment. Please be aware, that the only purpose of modelling equipment is the consideration of the thermal expansion. Within the pipe stress model you can’t perform a vessel calculation against internal pressure etc.
3) Calculation temperature is used to determine the allowable stresses, calculation pressure defines the primary stresses due to pressure (longitudinal).
Operation temperature is used for determination of y- modulus and thermal expansion. Operation pressure is used to calculation reaction forces and expansion due to internal pressure.
4) A Tee always expects 3 couplings (two of the run and one of the branch), you simply can “draw” the branch pipe onto the main run.
5) A blind flange is basically a flat end, where the head is a spherical end. A blind flange you can apply on the second side of a e.g. welded neck flange and a head on any end point of the pipe.
6) A point mass is a single mass which will act like the mass of the pipe itself. You could use it e.g. for representing the weight of a vacuum ring.
7) See end of post.
8) An axial stop is used to block the movement in axial (longitudinal) pipe direction.
9) This load case is a follow up load case of the operating load case. It supposed to consider the changing sign of the reaction force due to friction while shutdown. You should enter the operation conditions under shut down.
10) For the definition of the stress equations please have a look at the calculation code or the ROHR2stress manual. The S1 equation considers the primary stresses (weight+insulation+media+pressure), the S3 equation the secondary stresses and the S4 equation the combination of primary and secondary stresses.
In any case the S1 and S4 equations have to be fulfilled, the S3 equation can be exceeded as long the S4 equation is within the allowable limits.
11) The stress range combines all thermal load cases and is used to calculate the secondary stresses. Imagine for example a pipeline with a load case -50°C and +50°C. In these two load cases the resulting bending moments might have a different sign, e.g. -10kNm and +10kNm. The resulting range of bending moment will be 20kNm and this will be used to calculate the stresses.
12) You might have to edit the report template by using the “Documentation|Edit report template” function. There you can add placeholders to your template, which will be used as data links.
Regarding your second model you actually only have to reduce the distance of the long section between pt153 and pt151. After the calculation you will see, that you also will have to add supports, as the sections will “fall down”.

Best regards,
ROHRsupport

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