Design Guidelines

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

Design Guidelines

Beitrag von Mechanical Engineer »

Dear all,
I would kindly ask for information please.
1) Could you recommend good design guidelines (free of charge downloadable from Internet) on pipe stress thermal accommodation e.g. anchor placement strategy when pipes are branching off from main pipe (Shall I put fix anchor on main pipe next to pipe branches or branches next to main pipe ? Any suggestion is highly appreciated.
2) I am not sure how to treat pipe flange connection to AHU or fan coil. Shall flange be treated as fix anchor?
3) Most of piping system I am working on are 3D problems. What is general design strategy for accommodating thermal expansion e.g. to divide pipe network into sections with anchor positioned strategically to make L,Z,U compensation.
Thanks muchly
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rohr2support
Beiträge: 455
Registriert: Mi 14. Sep 2011, 08:23

Re: Design Guidelines

Beitrag von rohr2support »

Hi

1) Unfortunately we don't know a good, free piping design guideline on the internet.

2) Connections to equipement are often treated as rigid achor points (maybe including thermal anchor point movement) unless more detailed flexibility characteristics are known. The calculated anchor point loads are then checked against the allowable of the manufacturer.

3) Good pipe routing and supporting needs some considerations. While there are simple "heuristic rules" such as EN13480-3 appendix Q, these simple rules only treat the expansion between neighbouring piping sections without consideration of transmission of bending and torsional moment along a 3D piping system.
As a result, these methods give a subobtimal solutions for complex cases.

If you have a given routing of piping system a simple strategy could be:
  • position vertical supports at equal distances (based on piping diameter, medium and operation conditions)
  • Calculate a dead weight situation
  • replace all supports which are not required to be anchor points (such as piping ends and nozzles etc ) by constant support and calculate a "free" thermal expansion case
  • based on the deformation line, replace supports again by rigid supports such that they hindering of the "free" thermal expansion case is limited
  • add occasional loads like wind and earthquake to check that the pipe is sufficiently restraint
  • add more anchors if stresses from occasional loads are unacceptable, remove or move rigid supports if thermal expansion is overstressed
Best regards

Rohr2 Support
Mechanical Engineer
Beiträge: 8
Registriert: Di 8. Nov 2016, 09:17

Re: Design Guidelines

Beitrag von Mechanical Engineer »

Hello Sir,
Thank you very much for your feedback.
I did web search. Most of the topics deal with simple U,L,Z natural pipe compensation between fix anchors. Very little reliable literature sources (e.g. from manufacturers, case scenarios) is found on the web for complex situations. Perhaps for hot water flow temperatures and pressures e.g. 90/70C,NP6bar thermal expansion, stress issues are not significant. If the piping route is flexible enough e.g. natural L,Z,U bends could deal the problem successfully. However, for overheated water system and higher pressures e.g. 120/80C,NP16 , it would be very difficult to approach the problem successfully without available literature or good software tool such as ROHR2 and others.
If project cost is not of importance (which usually is not the case), another successful strategy would be to use Victaulic joints for pipe connections.
Much appreciated.
Kind regards,Sasa
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