Strange Welding Variables. 1

[InspectorClouseau]

Training required.

Would be interested to understand what people think of the variable as described in Table 4.11A item (m) in AS/NZS 1554.1:2014.

Preheat is determined as per clause 5.3, but is allowed to drop another 20 Deg C according to this variable, seems strange the 20 Deg C isn't mentioned in 5.3. It lowers the prheat to figures we don't feel comfortable with on the lower grades of steel. Also seems a bit strange that they call for an interpass temp within 20 Deg C of the PQR interpass temp - or am I missing something here...?

 

[kingnero]

Any chance you can post the relevant sections/tables from that standard?

 

[InspectorClouseau]

I don't want to break any copyright protocols for obvious reasons so I haven't posted any material from it here. I am really not sure of the rules relating to this and given what could transpire if I am seeing this correctly I think it best to stay on the safe side Gents.

But, if you do have a copy then also take a look at PWHT in AS/NZS 1554.1:2014. It isn't establishing the PWHT condition of the weldment as an essential variable, in fact not as a variable at all. It is stunning to me is this, so I thought I'd ask the wider community what they thought. Early feedback was that PWHT is out of the scope of 1554.1, scope doesn't say that, or put limits on thickness? So it looks to me superficially at least that you can weld, let's say, a 50 mm + thick butt weld with no PWHT, with no testing other than a macro to demonstrate its fitness for purpose and you are fully compliant with the Standard. This does not makes sense to me, what other Structural Steel Welding Code/Standard treats things so, and if there are others what is the science behind it please. It may help improve other codes may this!?

For seismic service they place a 300 Deg C max interpass temp limitation on WPS's, 4.6.1.3, that's normal. BUT, this "seismic" requirement does not appear to be classed as an essential variable in the EV table - why?

 

[DekDee]

IC,
"It lowers the prheat to figures we don't feel comfortable with on the lower grades of steel."

If you do not feel comfortable with it then write your own minimum on WPS.
The standard is a guide, you can apply more stringent conditions as you see fit.
(AWS D1.1 allows 15 degrees C so not a lot of difference especially when you take in to account the major climatic differences between the US and Australia)

Minimum preheat and minimum inter-run are basically the same thing.

Cheers,
Shane

 

[InspectorClouseau]

Thanks Shane,

Codes, Standards need to be safe on their own stand alone basis otherwise if they are not safe then they run the risk of being dangerous - especially in the wrong hands.
I won't write WPS's that are unsafe, others may well if they blindly follow, and, there are a lot of people who rely on this Standard to get it right for them in the absence of a degree of welding knowledge, including Governments - THIS is the concern.
In this part of the world it is any action or inaction, so to do nothing about a situation like what I think this is is just as bad as doing something dangerous. I'd imagine this piece of law would be much the same around the globe - would it not? It is also a nice feature of anybodies career to be involved with Standards that are sound, or, on the flip side, I do not want to subject myself to unsound practices described or provided for by Standards - what ever the case may be. My sense of responsibility tells me to get it fixed if it is wrong, not turn a blind eye.


Interpass is used throughout the world to typically describe THE MAXIMUM condition, i'e. Maximum interpass temp. Preheat is used to typically describe the Minimum condition the steel needs to be at to meet requirements good engineering practice before the arc is used to melt. i.e. the Minimum required preheat. I don't know of people who talk about maximum preheat [normally it is a struggle to get the thing up to temperature]and minimum interpass temp to describe the temp zone or range suitable for arc welding when discussing Structural Steel. For ASME P91 Cr Mo V material yep you are interested in a temp drop before PWHT but that is a different scenario all together - and not described by either term.

As a side note I've noticed they don't reference max permitted interpass temp to address their 300 Deg C limit on the matter, [perhaps they should instead of mixing the parameter with PH] is isn't even a recognised variable in the variables table. I am not comfortable with that approach at all - seems Mickey Duck.

What do you mean by the 15 Deg C comparison, what is that is relation to and does that include the 20 Deg C they say may be taken off in (m)? Is it that 1554.1 copies D1.1 to within 15 Deg C for preheats across the range of steel types and thicknesses...?
In 1554.1 take a look at the preheat temps for the group 1,2 & 3 steels - 0 Deg C for unlimited thickness...?? Then take 20 Deg C off for variable (m) -20 Deg C. Am I missing something, it just does not seem right. And this qualified by macro only??

https://www.youtube.com/watch?v=W7Ak5m9UX3c

 

[DekDee]

IC,
I hate AS/NZS 1554 with a passion.
I do everything I can to stay away from it.
One of the foremost experts on this code/standard is Graham Fry - do a Google search of Technoweld Australia and it should give you his contact details,
Cheers,
Shane

 

[InspectorClouseau]

I just wrote to them and told them just that, I know of no expat bar on our planet where people say that 1554 is cracker, in fact after they find out you're a Kiwi and after the sheep jokes have been dispatched with, we normally get straight down to "and how is 1554 these days, decided you need a PQR yet?" Earlier versions didn't even provide for a PQR even though I'd always prepare one. The looks, oh God the looks! Now if I can just get the PWHT in there, or scoped right out or a limit on thickness or some such mechanism to stop the rot, sort out the preheat and variable tables and and and and and and have it written by somebody who's first mother tongue is English, understands code architecture, Boolean logic and is literate I might just be able to be proud to be Kiwi.

I'd also told them people avoid it like the plague, including me so I don't learn its nutty isms. It's like watching a teenager spell, it simply messes you up - no response.

Now how would I go about making a change to the area I am in, I think Mechanical is closer to reality for me, I am not a Petroleum person, know nothing about it except the machinery that directs it.

That has been therapeutic - thank you very much Shane!

Shall we move over to the Welder Quals. Three standards for that under 1554.1, you have to prepare a qual addressing all three, they'll tell you two, but it is three. Bit like PDO days with six or seven layers of documents - eventually even the mighty PDO agreed it's impossible to comply with so many layers of standards all piled on top of each other - still doesn't stop AUS and NZL from repeating the feat - why should they miss out - and are we sure three layers is indeed enough Gentlemen. Now where's the Concierge.....

 

[DekDee]

IC,
If you are working in petroleum what are you doing with AS/NZS 1554 - pipe supports ?
And why are you so concerned about PWHT on structural items ?

 

[InspectorClouseau]

Have you heard of another structure code that does not address PWHT on unlimited thickness material qualified with a macro only? This appears to be a provision of 1554.1. There is no EV or NEV covering it, you can add it to your WPS just by writing it in, or leave it off, or turn up the heat, or turn it down and save some power and shorten the time at temp and whistle dixie, make it red, orange, its a great provision. No PQR required at all, no proof of effectiveness, just do what you want, no testing to verify anything. What code do you know allows this approach across the board?

 

[InspectorClouseau]

Some of the steels covered by 1554.1 can be upto 100 mm thick and are TMPC steels that do not like a PWHT over 620 Deg C. Even if there has been work done to reduce the thermal treatments traditionally reqd during fabrication I am not so sure there is no need for PWHT if you are butt welding thick sections. This is the type of thing you need to be acutely aware of, big thick sections of TMPC steels that will have their properties altered if they are heated above 620 Deg C during a PWHT. Easy done if there are no rules to guide you. Until somebody I know knows can tell me I do not need to carry this in the back of my mind I shall - always!

Now where's the good Dr. to tell me I'm wrong - the other blokes have all run for the hills.

 

[InspectorClouseau]

Thank you Eng-Tips.

The other variable issue in 1554.1 that annoys profusely is this neglecting to classify standard requirements as essential variables or non essential variables.

Once the Boolean nature of Welding Standards is understood then you can get real smart by playing the logic backwards to get Beethoven’s V th instead of Smoke on The Water. It is a way of checking you have got things right, logically, if you run it backwards. Goes something like this.
Why do we have WPS’s? So that all things that a welder has control over that makes the weldment suitable for service, suitable for service – for the joint under consideration. Everything s/he needs to know to achieve this is on one piece of paper or in one easy to access location for reference.
Why do we have a Code. So that all things that go into making a weldment suitable for service are addressed by the people who need to address them. For the welder we make a nice list for each joint called a WPS.
I can smell an equation, why don’t we say everything a welder has control over that is in code that affects the weldments suitability for service needs to be on a WPS, i.e. needs to be classed as a variable – and appear in the variable table waiting to be addressed by the user.
E.g. if Code says remove arc strikes outside the fusion faces by grinding and performing MPI - that goes on the WPS as a formal variable [I shall leave it to the infantly wise to decide what type of variable, and incidentally you need to know you have removed the affected microstructure of an arc strike not just do MPI on the site. Acid etching is a great way to do this and so very very much superior to MPI which doesn’t do that of course.] It does not stay buried in 125 pages of code for the hourly worker to read through each time s/he has to make a weld and ends up with a strike. They don’t even know they have to do something about it cause it aint on the WPS – right?
Now you have a list of stuff the welder has to comply with from the code, but you also have an inspection checklist.
Backing up a bit further, that then means because it is a variable it should be included on the variable table 4.11 for mandatory inclusion in the WPS. Stops things being kept secret.
Why are there so many mandatory requirements in this Standard/Code that a welder has control over that are not required to be on a WPS? It sets them up for failure. Is it secret society stuff “Oh the welders are not supposed to know those things” like what was once told to me about weld acceptance criteria. Ah there’s another essential variable & we all know where they belong, certainly not in some chart under some chapter heading Management of Quality. Too logical? Only in Spocks world? In my world the code pages are plastered on the walls and every welder is a damn expert on the bl00dy thing.
Then the competition starts, who knows the most about the codes, the welders or the QA. Perfect environment.

End the practice of failing to understand when you are describing an essential variable AND make sure you reference all variables the welder has control over in the variables table. On the flip side, help those that leave variables unaddressed by the variables tables buried deeply within standards to understand that they are setting everybody up for failure.

https://www.youtube.com/watch?v=tOCCvN8YDuc

Since there are NO essential variables or any materials variables listed in the variables tables at all for 1554.1 how about you and your mate see if you can list what they are in any case - for how else would you write a WPS if you are not clear on all the materials EV's. I've done the same - maybe we can compare notes....