Chris,
I work in the construction of very large offshore production platforms. The large contractors that build these like to use weldable primers, so I have a lot of experience with them. The fact that your spec names specific primers is not surprising to me. However, what is surprising (unless you just didn't mention it) is that they don't specify that the WPS be qualified with the specific primer, that the actual primer thickness for the PQT be measured, that this becomes the max thickness allowed on the WPS, that there be also a fillet weld break test, that there be a QC program in place to ensure that the max primer thickness is not exceeded on production joints, etc, etc. Weldable primer needs to be carefully managed. I've seen it cause many welding problems.
Mankenberg
I didn't see anything in the spec that called out that I had to run a PQR for this project, everything is regular D1.1.
You bring up a good point though and I found the data sheet for the primer, and it does list a mil thickness requirement not to exceed for "weldability". I called the technincal services department of Carboline and am waiting for him to call back. Basically I asked him what specific tests did they do to confirm it is ok to weld through, he could'nt find it easily so he'll look somemore and call me back.
In the meantime, D1.1 Clause 5 Fabrication says;
5:15 Preperation of Base Metal:
......."a thin rust-prohibitive coating, or anti-spatter compound may remain with the following exceptions"....
I abbreviated the paragraph to save time but it is allowed per the code, and as I intrepret it, it would be ok as pre-qualified becasue of the above statement.
Again, though we always remove it. I just posted this becasue it was the first time I had seen it in a project specification calling for it, which in my opinion is not only allowing it but actaully requiring it.
Thanks for you input.
Chris
For shop fabricated weldments that have field welds, it is usually preferred to avoid painting or galvanizing the field weld end preps. But they do need some protection from rusting until assembly to make them easier to prepare for field welding. Weld-thru coatings are usually used in lieu of leaving them bare or covering them with tape. The weld-thru coatings are also usually removed by wire brushing prior to welding. Some folks will weld over them with SMAW or FCAW and usually don't see any weldability issues. GTAW or GMAW without removal can lead to porosity problems.
Chris,
What is the DFT requirement in the job specs.? If it exceeds the weldable DFT, you have a bit of an issue. 0.75-1.25 is the weldable DFT, and I'd think that with this being a zinc rich primer, the required DFT as a protective coating would exceed that. I guess you could go lighter at the bevels. Surely they'll be touched up in the field after welding.
Deoxaluminite is not a zinc rich primer. This is why brand names are specified, some folks do not understand that they are not the same type of coating.
Marty,
The spec. sheet provided by Chris that was attached to his post is zinc rich. That's the one I was referring to. I'm not familiar with Deoxaluminite, but if it's not zinc rich, it seems kind of strange that the job specs would mention it as an acceptable primer along with one that is zinc rich because as you said, they're different types of coatings. I thought that they were very similar. Does the Deoxaluminite provide the same protection as the CarboWeld 11HS ?
Guys, I have been informed that the only strucutural parts we are providing are lintels, and they are not painted.
I was reading through the spec assuming we had the entire structural package and that this issue might affect me, but now it is not the case.
I have not had the time to look into the Deoxaluminite to see what it says, it's not a proirity now so I'm going to pass for now.
My initial reason to post the thread was to point out a spec that actually called for "weldable primer" because like I said earlier, I had never seen it called out, only that some people use it and others frown upon it.
I am glad to see others had seen it, at least it isn't new.
thanks Chris
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