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1st Jun 2020, 06:06 PM #1Novice
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AS/NZS 1554.1 - Preheat Calculation.
I'm having trouble getting my head around the provisions in AS/NZS1554.1 Structural Welding Code for preheat - wondering if somebody could shed some light?
If you go to clause 5.3 there is a method using graphs for determining the min preheat required. In section 5.4 - Weather Conditions, there is a further preheat requirement in that no preheat temp is to be below 0 Deg C unless the WPS is qualified IAW section 4. Looking at section 4 all WPS's need to be qualified IAW section 4 - even if only a written PQR & a macro examination is required to do so.
If you go to the table of essential variables - 4.11 (A)(m) it allows a 20 Deg C reduction is the preheat temp on the WPS.
Does this not then permit a -20 Deg C preheat for any WPS for which the graphs in 5.3 show a 0 Deg C preheat....?
Is this not a loop-hole/provision in the standard that needs to be addressed...?
Also the inter-run temp is not allowed to drop more than 20 DegC from that in the PQR - seems bizarre doesn't it? Normally inter-run temp is a maximum and preheat is a minimum, so long as your preheat is maintained and you do not go above the max permitted inter-run temp then who cares how much the inter-run temp drops, in fact it can be an advantage not to approach the max permitted inter-run temp to help control grain growth and maintain fracture toughness....??
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1st Jun 2020, 08:42 PM #2
Not my gig, and have not seen the clauses you refer to... but have you discussed with the engineer or inspector who is drawing up the job / inspecting the work?
Failing that are you a member of any industry bodies (eg WTIA, formerly Weld Australia) who may be able to offer advice?
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4th Jun 2020, 12:40 PM #3
Hi Leaner,
What year is your AS 1554.1
If it is an older one there is every chance that the problem has been queried already and acted upon.To me it sounds very much like a printers error.
Every so often they print an Addendum page ( you can pick it out-its green ) which addresses errors and discrepancies printed in the original.
If you purchased the code you will be aware it is expensive.They are e$$pensive because they are short print run documents and the addendum has been the way of cheaply updating until they rewrite the particular code to allow for new technology and new methods.
Long story made short,chase up the addendum.
Grahame
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4th Jun 2020, 01:11 PM #4Novice
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Good point Grahame. 2014 is the edition I have, which I think is the latest, to this there are two amendments one to do with fillet sizes and the other to do with Boron content....
I think we all know not to weld below 0 Deg C and in fact not to weld below the due point on steel otherwise you run the risk of welding in the damp or wet which is not good from a HIC point of view. Just seemed like a hole in the code that should be addressed otherwise you'll have people taking advantage in frost, alpine or refrigeration type conditions, or even in Antarctica where I think the code applies to the NZL facilities at least...??
Since loosing Chris Smallbone people have noticed that there has been a culture change at WA. They tend not to be as accessible on many levels as they once were.
Notice also how the code does not address post weld heat treatment at all. Meaning you can use a weld procedure with no PWHT and perform a post weld heat treatment on it, even drop the red hot steel into a bucket of water and still be fully compliant with the code's provisions. To me that is dangerous. Or to flip it around the other way; you can take a weld procedure qualified with PWHT and leave out the PWHT. A code is there to prevent these types of things. I don't think there is a code on the planet that allows this, they all address PWHT in some way or another.
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