how to understand the Minimum leak path dimension of QW-193

牛丫丫

Hi all , when you read the QW-193,  the acceptance criteria of Macro-Examination, you may see the "Minimum leak path dimension---------" , So, who can explain it to us for understanding?  

牛丫丫

Great! For those who build heat exchangers, Section IX has added rules to QW-193 for
making tube-to-tubesheet welds. These rules are very similar to those found in Section
VIII, Division 2, Article F-3 and identical to the rules in Section III, NB/C/D-
4350.
Tube-to-tubesheet welding is qualified by welding ten mock-ups of the tube-totubesheet
joints using the same geometry holes in the tubesheet and the same tube
size and thickness as that to be used in production. Testing consists of performing
liquid penetrant examination followed by cross-sectioning of each joint and examining
it at 10X magnification for cracks or flaws. The minimum leak path (distance
from the root of the weld to the surface nearest the root) must equal that required
by the design or by the Construction Code, typically two-thirds of the tube thickness.
The new Section IX tube-to-tubesheet welding rules only become mandatory when
the applicable Construction Code (Section VIII, Section III, etc.) invokes them. If
they are not invoked, tube to tubesheet welds have to be qualified by groove or fillet
weld testing. Both Sections VIII and III are proceeding to drop their rules for tubeto-
tubesheet welding and will be referring to the Section IX rules in the future.
Those accustomed to following the Section VIII rules should be aware that the Section
IX rules have added current, current type and polarity, type of welding (manual,
machine, etc.), diameter, progression, cleaning method and the addition of expansion
prior to welding to the list of essential variables. Whether or not WPSs qualified under old Section VIII rules would be acceptable for new work once the
Section IX rules are adopted by Section VIII would have to be addressed by Subcommittee
VIII by inquiry. For welder and welding operator qualification, QW-
305.5 specifies that the standard rules for groove and fillet weld qualification apply
when the WPS is qualified by groove or fillet weld test, but if the WPS is qualified
by mock-up, the welder or welding operator has to be qualified by mock-up.

lwycumt

这个我也没查到具体什么含义，你可以参考下这个帖子里讨论的
http://www.maihanji.com/bbs/showcontent.asp?id=30223

lang21

对于这个问题我有跟哈特福德的AI交流过，他的理解是从焊缝根部到焊缝表面的最近的距离，说白了就是有可能泄漏的最小的厚度。

牛丫丫

This is one of the questions that some one asked me several days ago, he was confused by the translations of "最小泄露通道尺寸“，hopefully,  the above may help us understand this well.

viliant

谢谢分享，虽然不知所云