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SIX and SIF factors in BENDFAC table
29-01-2017, 09:56 PM, (This post was last modified: 29-01-2017, 10:03 PM by shaswin.)
#1
SIX and SIF factors in BENDFAC table
When rerounding due to internal pressure is taken into account the loadfactor PRESS-F shouldn't be applied here. It will reduce the SIX and SIF factors.
   
Press should be 1.00 MPa instead of 1.15 MPa. This makes the SIX and SIF more safer.

I have a question about how the K, SIX and SIF are calculated in the 'General' Option. When I manual calculate with the following formulaes another values are calculated then the Educational version. I can't reproduce it the SIX and SIF in the 'General' Option:

   

   

I have to do some SIX and SIF corrections due to miter bends.


Attached Files
.zip   Test Edu.zip (Size: 195.4 KB / Downloads: 2)
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03-02-2017, 12:20 PM, (This post was last modified: 08-02-2017, 09:06 AM by Dr. J Foerster.)
#2
RE: SIX and SIF factors in BENDFAC table
You mention two different issues here:

1) The usage of the pressure load factor.
You are right, if the factor is set to 1 during calculation of SIX and SIF, the results become safer / more conservative.
This is actually done when using the NEN 3650 calculation option (not available in the educational version).
When calculating "general", we decided to apply the pressure load factor as we feel that the results would be too conservative otherwise.

2) Calculation of the K, SIX and SIF factors.
The calculation differs when using the NEN option or the General option.
In case of a NEN calculation the formula's you mention are used.
In case of a general calculation more complex formula's based on Clark & Reissner-ASME/TNO) are used:
   
This explains the differences between your manual calculations and the results in Ple4Win.
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04-02-2017, 12:54 PM, (This post was last modified: 08-02-2017, 09:09 AM by Dr. J Foerster.)
#3
RE: SIX and SIF factors in BENDFAC table
Jens,

Thanks for your reply.

In point 1 you are meaning NEN 3650 instead of NEN 3630 Wink. [note: right, corrected]

What I also know is, that the calculation of the rerounding factor the loadfactor had been removed in Ple4Win in the past. The loadfactor for the internal pressure is also not applied in the following formulae in the NEN calculations:

   

Consider you have a 'General' option calculation with for example the loadfactor 1.88 conform Rotterdam handbook for Pipelines. Then the SIX and SIF are very optimistic for the bends in the BENDFAC table. Is this still safe? According to the code NEN 3650-2:2012 (table 2 footnote a) multiplying with a loadfactor 0.9 should be used in the case where multiplying with a loadfactor is not working safely:
   
The loadfactor 0.9 should also be taken into account the rerounding factor. Currently Ple4Win uses a loadfactor 1.0 for the internal pressure of the f_rr formulae.

For point 2:
The formulae for SIX and SIF are also different then in the 'General' Option. Can you give a screenshot which formulas are used for SIX and SIF in the 'General' option? So I can do a miter bend correction in the 'General' option without to open Ple4Win every time to check the SIX and SIF every time for every bend in the 'General' option.

According to the text in the attached document "mijterbocht.pdf" the calculation of miter bends would be implemented in the future of Ple4Win (this was written a long time ago):

   

I have also opened a new topic about SIX and SIF here. There might be an open issue in the NEN 3650-1 code.


Attached Files
.pdf   mijterbocht.pdf (Size: 50.99 KB / Downloads: 0)
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