Qualify 3G position cover all position when require CVN 1

[Thuhuongengineer]

According to table 4.1 in AWS D1.1 when we qualify 3G position we will weld only Vertical position. However table 4.6 statement "A change in position to vertical up. A 3G vertical up test qualifies for all positions and vertical down" Thus 3G postion cover for all postion when apply CVN test. When not require CVN 3G cover only Vertical position (3G).

Why 5G-Vertical postion cannot cover all position because 3G and 5G only difference is 3G apply for Plate, 5G apply for Tubular.

Pls clariy for me understand!

 

[pandithan]

5G will not cover 2G position, 6G will cover all position, Donot relate with CVN requirement because in out of all positins, 3G vertical Uphill will generate more heat input which is harm full for CVN
pandithan

 

[DekDee]

Table 4.5 lists the Essential Variables.
Table 4.6 lists Supplementary (or additional Essential Variables)
So, 3G only qualifies 3G

What Clause (6) in Table 4.6 means is impact testing of a coupon in the 3G vertical up position qualifies all other positions.
In other words if you have qualified procedures for 1G, 2G, 3G & 4G you only need to perform impacts on the 3G coupon - you do not have to perform impacts on all 4 positions.

This is from the Commentary (C4.8)
In Table 4.6, the Essential Variable on line 6 eliminates
the need for CVN testing in all positions but does
not change the requirements of Table 4.5 regarding welding
positions.
Hope that helps,
Cheers,
DD

 

[Thuhuongengineer]

Thank Dekdee,
I am clear this question.

 

[wegm]

As DekDee told, requirements of Table 4.6 could be considered as "additional Essential Variables", please have a look at this link that gives an example for qualification of two procedures that vary only to position as well as gives the metallurgical explanation of the worse CVN testing results that referenced by pandithan:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=15&t=397

 

[gtaw]

I tend to be suspicious of forums/blogs that don't identify the principals involved or the "ownership" of the site.

Best regards - Al