American Welding Society Forum
I was curious how many of you have used Annex XI (Hydrogen Control Method) of the D1.1 to determine preheat and interpass temperatures?
I have several projects which specify the use of the Annex in lieu of Table 3.2. The preheats as determined by the MTR's submitted all require what I consider to be excessive preheat (e.g.: A572, Gr. 50 with a T of 5/16" = 280 degrees F.) I had a P.E. check my calculation, and they were accurate.
I feel this is due to the micro-alloying that occurs as the materials' mechanical properties keep going up with recycling. The Engineer who checked my numbers agrees and noted some of the high percentages of elements noted in the MTR's, particularly C, Mn and Si. We even tried the calcs. on MTR's whcih appeared to have low pecentages of alloying elements.
Any thoughts from the Forum on this subject?
I have used Annex XI when required for offshore structural work. The specifications usually specify to use the high restraint and we end up with 300F or 320F preheat usually. Sometimes though, they allow reduction of preheat by conducting a controlled thermal severity tests (CTS) conducted at the minimum preheat to be used with the lowest heat input to be used. So far we have passed this test at room temperature for a 50YS cast alloy and HY80 at 320F (had to do this one to verify no PHWT cracking instead of preheat reduction). I agree with your assesment of the recycling situation. We make castings from scrap plate/sheet/casting returns, and it is hard for us to keep the Cr under .2 or the Mo under .15. Too much alloy in our melt stock.
We qualified a PQR using the D1.1 Table 3.1 preheat and all of our test results including impact far exceeded the minimum required by the RDP.
The engineer is not sure what Annex XI is reallly for, nor does he understand the purpose of this annex and has admitted this fact. He just states that is what he wants.
The commentary at the end of D1.1 contains some explanation as to how annex XI was developed. (page 435 of the 200 code) If this project is extensive, it may be worth it to convince the engineer to accept a preheat determined by testing with a CTS test.
I have ran into those type engineers before. Don't have a clue but they want it anyway just because they said so.
My client has for the most part thrown in the towel. The engineer and proponent are imposing new rules everyday. Now they want us to test every heat of FCAW wire. They (the fabricator) are now choosing the path (which I recommended 3 months ago) to dig in deep and hold their ground.
Again, we proved our preheat by testing. We are not making any more changes to the WPS's or PQR. The steel has been sitting in this shop for 3 months. How many of you guys can hold your breath that long?
Have another one of these sitting here John, maybe I'll send it back.
How do you spell relief? C-H-A-N-G-E O-R-D-E-R!
It sounds like you have a fracture critical job there. Just an observation, D1.5 section 12 does not require heat/lot testing of filler metals and fluxes, IF they are produced by a manufacturer who is operating under a certified quality program such as Lloyds, ASME, and etc. I've found that most all major companies do that. I don't know if D1.5 applies in your case but it works for bridges.
Annex XI is intended for predicting adequate preheats lower than Table 3.1 lists or for unusual situations where higher preheats may be warranted. However, both the text and the commentary indicate Annex XI is a guideline to be applied with common sense. If you have done some testing with the material and processes to be used and everything was OK, then Annex XI is not needed.
Sounds like you have all the fun.
Hope it works out,
I will be compensated for my time (including each time I have to re-issue the WPS's and PQR), but my performance is also in the interest of my client (the fabricator) as well. I have been outspoken on this subject, but my client is concerned about politics. I would think the $$ they have wasted messing around with this for so long would have been the indicator that it is time to quit screwing around and move on.
SMRF's are fracture critical, but not like a bridge. D1.5 does not apply here, but you would think it did based on the project specifications. The D1.5 FCP is not contractual in this situation.
The RDP's specifications are lengthy, but he has to look to others to get an interpretation of his own specs...
All of the "required changes" that we have been asked to make are not in our contract, bid documents, the code, nor in any changeorder. These guys just think we should do.
Some of these changes (to name a few) have been:
a.) change the root opening for fillets from 3/16" to 1/16"
b.) change the amperage from 225 to 250 (to a number that is exactly like that of LIncolns recommended numbers)
c.) This is a good one: Make the WPS only for this project(?), The proponent has stated these WPS's can only be used for this project (again with the ??)
Yes. Yes I am having fun.
This sounds like a client we had that didn't know that much about welding, but was reading some stuff and kept asking for anything they read about that was beneficial for the situation in their reading, but may or may not have any beneficial effects on the welding at hand. We had to just keep telling them how much time and money everything would take, and they backed off of 90% of their requests. I have never heard of conformance testing for every lot of FCAW electrode for structural work. We have to do that sometimes, but it is for Nuclear work, or submarine parts and the like. You aren't bulidng a reactor are you?
I think clients get like that when they are scared something will go wrong, but the price and schedule usually scare them even more. I'm glad I don't have that client, we have enough of our own like that!!
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