NDE inspection method of welds after galvanized
NDE inspection method of welds after galvanized
(OP)
Hello,
We have A 572 structural steel components of transmission towers welded then hot dip galvanized (Zinc coating). I would like to know which is the best NDE method to check weld cracks after glavanizing and why the method is good? Your responses will be greatly appreciated
We have A 572 structural steel components of transmission towers welded then hot dip galvanized (Zinc coating). I would like to know which is the best NDE method to check weld cracks after glavanizing and why the method is good? Your responses will be greatly appreciated





RE: NDE inspection method of welds after galvanized
RE: NDE inspection method of welds after galvanized
before hot dip galvanizing. After galvanizing would be a visual, which is really not cost effective or practical.
RE: NDE inspection method of welds after galvanized
You may hear "that isn't how we do it", and that will be because they rely on HDG to hid weld defects.
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Plymouth Tube
RE: NDE inspection method of welds after galvanized
Regards
aadpilma
RE: NDE inspection method of welds after galvanized
I would presume HDG would fall under the same criteria as paint (although not specifically noted in AWS D1.1)
5.30.2 Cleaning of Completed Welds. Slag shall be removed
from all completed welds, and the weld and adjacent
base metal shall be cleaned by brushing or other
suitable means. Tightly adherent spatter remaining after
the cleaning operation is acceptable, unless its removal
is required for the purpose of NDT. Welded joints shall
not be painted until after welding has been completed
and the weld accepted.
Regards,
Kiwi
RE: NDE inspection method of welds after galvanized
Bruce, Nichols Technology
RE: NDE inspection method of welds after galvanized
Here are a copy articles, though several years ago, that may be helpful:
http://www.aws.org/itrends/2005/10/023/
http://www.aws.org/itrends/2004/07/it0704-29.pdf
Richard www.6sproductivitycom.com
RE: NDE inspection method of welds after galvanized
Why would cracking occur due to hot dip galvanizing? Heating and cooling effect on the thin members typical of towers?
RE: NDE inspection method of welds after galvanized
From page 35 NYRSTAR Half Year Report 2008 report
"Galveco
Galveco is a patent-protected zinc alloy used for galvanising steel. Between June 2000 and March 2007, Umicore produced and supplied (approximately) 45Kt of Galveco to galvanisers in various countries (corresponding to approximately 3.5Mt of steel that
has been galvanised with Galveco). Umicore withdrew Galveco from the market in March 2007 as a precautionary measure following the discovering of cracking in steel that had been hot dip galvanised. It is alleged that a cause of this cracking is the
use of Galveco."
Influence of Various Parameters on Steel Cracking During Galvanizing
(Presented at the AGA TechForum 2003 in Kansas, MO)
Graham Poag and John Zervoudis
Teck Cominco Metals Ltd.
Product Technology Centre
"When levels of tin or bismuth exceeded approximately 0.2%, the size of cracks
became greater than those obtained in samples from a PW bath, often exceeding
1 in. (25.4 mm) in length. As tin levels increased above 0.3%, crack size
continued to increase, whereas the extent of cracking did not seem to increase
further as bismuth levels increased above 0.2%. " http://reddogalaska.com/tc/gg/pdf/presentations/AG...
Current Knowledge of the Cracking of Steels During Galvanizing
http://www.aisc.org/uploadedFiles/Research/Researc...
A Review of Bath Alloy Additives and their Impact on the Quality of the Galvanized Coating http://www.teck.com/tc/gg/pdf/presentations/apggc_...
http://www.ing.be/xpedio/groups/internet/@public/@...
Galvanizing Structural Steelwork - An approach to the management of Liquid Metal Assisted Cracking https://www.steelconstruction.org/resources/public...
https://www.steelconstruction.org/component/docume...
Richard www.6sproductivitycom.com
RE: NDE inspection method of welds after galvanized
So the Liquid Metal Assisted Cracking in this reference is comparable to the terms LME or LMIE used above?
RE: NDE inspection method of welds after galvanized
I found the above publications by Rich2001 interesting. To me, taking the issue of molten zing during welding out of the equation, iron-zinc LMIE during galvanizing is related to impurities within the molten zinc bath rather than liquid zinc itself. Over my career, I have seen numerous transmission and distribution hardware manufactured within the US while working for a large electric utility and not once did I ever come across a situation where galvanized pole hardware and tower steel developed LMIE cracking. I think just like anything else in a global economy as lowest cost becomes a driver, galvanizers will not watch their impurity levels or use additives where suddenly what was a non-issue becomes an issue under certain conditions.
All this means is that the purchaser needs to be involved with the galvanizing process and ask questions related to purity of the molten zinc bath.