Joint Efficiency values

[cespi82]

Hello all!

My understanding is that JE is the ratio of the strength of joint to the strength of the base material. I've been trying to find out how the Joint Efficiency (JE) values were determined by ASME?

For example, how did ASME determined that for a Type 1 joint without radiography the JE value is 0.7? How did the established that the strength of a type 1 joint without radiography is 70% of the strength of the base metal?

I have also noted that these values have changed from past and old editions of the ASME BPVC. When was the last change?

Regards!

 

[BJI]

You might appreciate the discussion in this referenced paper on the history of weld joint efficiency if you have access, probably not worth purchasing just for the discussion though. w

http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2660433

 

[TGS4]

The joint efficiency factors are effectively penalty factors for not doing enough weld inspection. There is no scientific or engineering basis for these numbers except that a group of engineers decided that the current numbers seem appropriate. And there is no desire amongst the current Code Committee members to reopen or revisit the values.

 

[XL83NL]

I guess the OP is more looking into the history of the numbers, so why exactly was it set to 70% by that group of engineers, and not e.g. 65%, rather than that he's looking for reason to change the current Code.

 

[TGS4]

There's no technical reason/justification for any of the numbers - as Frith and Laird laid out in their paper that BJI linked to. They are entirely empirical.

Your best bet would be to find a time-machine and ask that group of engineers.

 

[MGZmechanical]

Hi, not sure about the origin but are similar in the European codes. Without testing 0.7, with certain degree of testing 0.85 and with detailed testing 1.
In any case in the european code pressure vessels are categorized depending on the Volume·Pressure figure and the danger of the fluid (gas or liguid, explosive or not, ...). The level 0.7 (no testing) it's only applicable with the lowest category.

 

[cespi82]

Thank you all for your replies. At least a have an idea that there's nothing really sophisticated behind those values.

Does any of you have access to that paper? If you do and do not mind sharing it, could you please email it to me? (cespinoza82@gmail.com)

Kind regards!