Re: [PipingDesign] Mitre bend Calcultion

From: <Tony>
Date: Mon Jul 28 2003 - 11:59:00 EDT

>Can anyone guide me how to calculate teh mitre joint calcultions for large
>diameter pipe.

Christopher wrote:

There is no closed form calculation.I've seen some numerical methods for doing this calculation (Do a search at <http://www.scirus.com> or <http://www.google.com> FEA is quicker, but it's not a trivial problem. The stresses are non-uniform around the miter and comprise both primary and peak stresses which have to be sorted out because different allowable stresses apply.

In addition we would say:
The B31.3 code equations mentioned below by Tushar in conjunction with Appendix D expressions for stress intensification factors tend to serve well for most miters in PVP applications. We consider pipe to be of large diameter when D/T>100. The 100 limit is found in the notes to B31.3 Appendix D. When the D/T ratios get larger than this you tend to get handling related and support problems. Fatigue is another issue not well addressed for large D/T pipe but is not often seen, i.e. most systems do not cycle more than 5000 times in their life, and this is where the B31 Code safety factors reduce to values in the range of 2.

Large valves or fittings within a diameter of the miter can effect the stress in the miter because of the restriction to ovalization. There are recommendations pending to provide this length definition to the rules for SIF's and attached flanges. For the FEA models we've run external pressure on large miters tends not to be a problem as long as you use the standard ASME VIII external pressure rules for stiffening.

FEA Software we write and sell builds the miter joints automatically, but building the model is only a part of the problem. You must plan on spending at least a few days scratching your head wondering how to take the pretty plots and relate them to practical piping designs. (My opinion only.)

Regards,
A.Paulin

From: zope_tushar@fwuk.fwc.com

   To: PipingDesign@yahoogroups.com
   Sent: Monday, July 28, 2003 4:14 AM
   Subject: Re: [PipingDesign] Mitre bend Calcultion

   Md Danish,

   For miter bend calculations, please refer to the equations (4a), (4b) or    (4c) of para 304.2.3 of ANSI B31.3 Piping Code.    Miter bends generally have pressure limitation and this can be calculated    by the above eqations.

   Best Regards.

   Tushar

                         "Md Danish"
                         <danish_petro@yah        To:
   PipingDesign@yahoogroups.com
                         oo.com>                  cc:
                                                  Subject:  [PipingDesign] Mitre
   bend Calcultion
                         28/07/2003 14:15
                         Please respond to
                         PipingDesign




   Dear All,
   Can anyone guide me how to calculate teh mitre joint calcultions for large    diameter pipe.
   Please do provide me with the formula for doing the calcultions and the    relevant material available on the sites.    Thanks & Regards,
   M Danish



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[Non-text portions of this message have been removed] Received on Mon Jul 28 11:59:00 2003

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