Weld strength reduction factor difference in thickness equations

[NovaStark]

Hi all,

The facility that I work in was constructed using the B31.3 2004 edition. So piping minimum thicknesses are calculated using this edition.

Have used the 2008 edition and beyond, I saw that the W factor was introduced in 2004 however only one of the thickness equations whilst from 2006 and beyond has it in both equations.

Is there any addendum or interpretations/reasoning for the omission in the 2004 edition? I couldn't seem to find any. So calculation of tmin would find things acceptable whilst the 2006 edition and beyond would deem it unacceptable.

2004 Code

2006 Code

 

[GD2]

NovaStark,
Code revisions are very normal. With new materials evolving and manufacturing quality standards improving, code committee included more and more materials in its acceptable list of materials and higher stress allowable. On the same basics, more and more material study is done and code equations are twigged to accommodate these changes.

When your project was built with 2004 code version, that was perfectly fine because that was the published version at that time but if you are to built a new faculty today, you have to use the latest code version. The project DBM will state the applicable codes to be used for the project and approved by the management. If a facility is being built today with 2016 code edition and 2018 edition comes up while the project continues till 2019, the project will be still good with 2016 edition.

Ganga D. Deka, P. Eng
Canada

 

[LittleInch]

Also W only comes into play (<1) at temperatures above 425C / 800F.

If you're at those temperatures then I suspect you have other issues....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[NovaStark]

Code revisions are very normal. With new materials evolving and manufacturing quality standards improving, code committee included more and more materials in its acceptable list of materials and higher stress allowable. On the same basics, more and more material study is done and code equations are twigged to accommodate these changes.

Understood.

When your project was built with 2004 code version, that was perfectly fine because that was the published version at that time but if you are to built a new faculty today, you have to use the latest code version. The project DBM will state the applicable codes to be used for the project and approved by the management. If a facility is being built today with 2016 code edition and 2018 edition comes up while the project continues till 2019, the project will be still good with 2016 edition.

My query comes into play when I look at the two equations for the 2004 edition, where using the OD (D), the thickness equation does not consider W yet when using the ID (d), W is considered.

Also W only comes into play (<1) at temperatures above 425C / 800F.

If you're at those temperatures then I suspect you have other issues....

The pipe I am referring to is around 1300F and made from 304H SS, so W<1 in this case.

Now using the 2004 code wherein the W factor is not in the OD equation, I get say sch. 120, yet if I use a later edition (where W is in the OD equation) then I may require schedule 160.

So my issue is really do I say my pipe is to code and thus does not require an increase in thickness based on what it is built to or do I say that I need a thicker pipe as latest design code deems this unfit due to a change in the equation resulting from as GD2 says code revisions are done based on essentially refined information or new information.

 

[StoneCold]

NovaStark
If you are installing new piping systems in the facility, use the current code requirements.
If you are modifying an existing system AND you are not having problems with the piping designed to the old code, continue using that code to validate the piping changes.
If your having problems, they might be resolved by following the newer code, they might not.

Thats my thought on the issue.

Regards
StoneCold

 

[NovaStark]

Thanks for the advice.

I wanted to know as I would not want my piping to be at risk with the logic to be "well it's to the original design code even though newer codes say otherwise".

(Kind of similar to how the Nelson curves change for susceptibility to HTHA)