Cracked Boom Pictures! Suggestions?

[oceanobob]

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... one aspect..... the number of terminations caused by the welder .... introduce flaws in the weld ...... which is why I would prefer a wire feeder.

When I was taught to repair weld, the instructor(s) insisted we learn how to backstep the welding. I am glad this point about 'starts and stops; was mentioned - perhaps it will solicit some comments pertaining to backstepping a weld.

I figured everyone would consider the backstep procedure when doing a crack repair.

And thanks for your comments on the higher impact property "repair rod" - this is what I was inquiring about....although another company was in my memory that we learned about, but it was a stick rod that performed especially well for making repairs, given the typical challenges. I recall it was notably more expensive than a box of fresh 7018.....

 

[Nige]

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When I was taught to repair weld, the instructor(s) insisted we learn how to backstep the welding. I am glad this point about 'starts and stops; was mentioned - perhaps it will solicit some comments pertaining to backstepping a weld.

I figured everyone would consider the backstep procedure when doing a crack repair.

And thanks for your comments on the higher impact property "repair rod" - this is what I was inquiring about....although another company was in my memory that we learned about, but it was a stick rod that performed especially well for making repairs, given the typical challenges. I recall it was notably more expensive than a box of fresh 7018.....

The price of Nucleotec Xuper 2222 might well make your eyes water, but if you're a fully paid-up member of the "fix it once, fix it right" association then it's a good choice and gives you a better chance of success.

 

[ih100]

However, to disagree on one aspect. I think that the low-hydrogen stick is a good repair tool, but on long welds the number of terminations caused by the welder "running out of rod" and having to change over can easily introduce flaws in the weld however good the welder who's doing the job, which is why I would prefer a wire feeder.

Agree with everything you say except this bit, Nige. A good welder won't introduce flaws at the stop/start, otherwise we'd see a lot more pipeline/rig/structural failures where stick has been used on critical joints. An indifferent welder might, though.

Also no-one has mentioned stringer beading to reduce stress build up, so I am.

 

[Nige]

I wouldn't disagree with what you say when you mention "a good welder". However the problem on repair welding is that generally it doesn't attract the type of top-class coded welders that usually end up things like doing pipework and nuclear sh1t that's all 100% X-Ray afterwards. We get the dregs (in general terms) and if anything can be done to the process to improve it to reduce the number of re-do's caused by process failures then I'm all for it.

 

[Karl Robbers]

I'd echo everything Karl has said and add to it that as an aid to stress relief I would needle peen after every weld pass. Also after completion I would recommend grinding the whole thing back smooth and tapering out any radiuses, etc, in order to further reduce stresses.

However, to disagree on one aspect. I think that the low-hydrogen stick is a good repair tool, but on long welds the number of terminations caused by the welder "running out of rod" and having to change over can easily introduce flaws in the weld however good the welder who's doing the job, which is why I would prefer a wire feeder.

That is a valid point, albeit one that rarely raises it's head with a competent operator.
The ultimate would be to use FCAW, which is gas shielded, (usually CO2), flux cored mig. This would offer the ability to perform the continuous welds that a solid wire Mig can allied with the toughness and ductility of Low Hydrogen electrodes. Stick has one major advantage and always will have, over mig or fcaw, this being the ability to access tight joints far more effectively, (notwithstanding that we should be aiming for our 60 degree vee, a j or a u prep).
It pays to remember that gas and oil pipelines are typically welded with the good old stick welder, often to x-ray standard, (very few welds performed by certified operators fail by the way).
Ultimately we all tend to use what we have at our disposal, that's where knowledge of procedures and workmanship come into play.

 

[Nige]

Again, can't disagree with anything you wrote, but you will insist on using that word "competent" .............. I have no experience of pipeline work other than walking dragline boom assembly and we had some excellent welders on those. Never a fail on X-Ray and all welded with stick.

However at the risk of repeating myself the average welder in a mine maintenance department is far from being "competent" in my experience. Don't get me wrong, I've come across some superstars in my years in the business but they were so few and far between that I can probably remember each one of them by name.

 

[Karl Robbers]

Again, can't disagree with anything you wrote, but you will insist on using that word "competent" .............. I have no experience of pipeline work other than walking dragline boom assembly and we had some excellent welders on those. Never a fail on X-Ray and all welded with stick.

However at the risk of repeating myself the average welder in a mine maintenance department is far from being "competent" in my experience. Don't get me wrong, I've come across some superstars in my years in the business but they were so few and far between that I can probably remember each one of them by name.

I can certainly see where you are coming from regarding the competence level of some welders on mine sites - I currently work in the mining industry.
At the mine where I work, a job such as this one would only be undertaken by our qualified boilermaker/s but the fitters would be allowed to undertake more basic repairs due to the reasons you have given. In fact the strict regulations that mines work under really preclude any other situation.
I certainly did not and do not want to appear argumentative as regards my position on stick versus solid wire mig, but speaking as a qualified and certified boilermaker, the trend I notice is that many times people choose migs as the best tool when they may well not be. Probably due to their perceived ease of use.
I understand for sure what you say about the potential for inclusions and flaws on the multiple restarts required with stick but migs have their areas of fault also and only perform at this level in the hands of, dare I say it, a competent operator.
All the best, I enjoy reading your posts.

 

[oceanobob]

The impact properties have to do with energy absorption and are typically associated with a test known as a Charpy. The key point about the Charpy is the test begins with a flaw (a notch), then the load (a swinging hammer) is applied. The material will absorb a certain amount of energy before it separates.
Applying the thinking there is always a 'flaw' (maybe a non-preferred design, maybe weld stress, maybe an inclusion from a weld, maybe a small amount of undercut, etc) {you get the idea** the Charpy will tell you how well that material will perform as far as being likely to crack all the way or maybe, just hopefully, self arrest the crack.
*
That story above is why I was asking about those 'repair stick rods' - they claim to have much higher values than 7018 for impact properties and are supposedly easier to weld in difficult conditions.
My review of impact properties on wire feeding vs 7018 stick makes me unsure of these wire products for use in crack repair:
A dual shield at -20 is about 25 to 35 ft lb
Core shield 08 (a favored structural steel FCAW wire) at -40 is about 43 ft lb
A 1% nickel added wire can be at -40 about 108 ft lb
and
7018 stick can be at -20 about 170 ft lb for good ole Atom Arc
*
We have every type of Mig at our shop, and when it comes time to "sign your name on a fix", the 7018 rod is used along with most or all the other tasks mentioned previously on this topic ( although opening up an access hole is a new idea to me).
All the 'old sage' weldors have instructed me to use 7018 stick for repair welds. A recent informal poll of a few mechanics at the local dealers (Case and John Deere) both inside and outside as well as the equipment repair machine shops all vote for stick 7018.
*
As for me, I was just inquiring if there were any better stick rods that anyone has tried. I think the original inquirer has received very good feedback. And, as much as I like my wire feeders, I respectfully thank all of you but am too nervous to use a Mig to do these types of jobs.

 

[yank132]

In all likelihood the crack pictured is indicative (as Craft ‘theorized’ in post #10) of at least one inherent design/process flaw.

Craft’s musing that this crack (and other similar cracks) might be attributed to the early stages of robotic welding that possibly contributed to a penetration problem was no crackpot ‘theory’.

If only such issues were just of historical interest. Unfortunately they still have a daily impact on heavy equipment manufacturing globally.

The inverter based systems used for robotic welding, by design, produce an inherently inferior outcome compared to a traditional transformer based CV power source.

The output slope from a multi-process inverter based CC/CV power source is typically steeper (ie. it delivers less current AND produces less fusion) than the output of a traditional transformer based CV power source.

Also, with many CC/CV pulsed machines you can end up with LESS weld fusion and MORE porosity, especially on steel applications over 5 mm thick.

The fact is, the majority of electronics in today's MIG equipment offers limited real world benefits when welding low carbon and alloy steels.

The last thing any welding operation needs is a MIG welder with a computer!

But can you name me one 1st tier global manufacturer still using transformer based CV MIG welders?

And the majority of the equipment talked about on this forum is reliant upon the MIG welding process!

Adding insult to injury, the majority of weld shops use the wrong type of gas shielded flux cored wires (if they use them at all), the wrong size MIG wires, and the wrong type of shielding gas.

Paraphrasing Charles Darwin, "If the evolution of mankind was measured against the technical progress that has taken place in the typical global welding enterprise, we would all still be swinging in the trees".

As the 1st Duke of Wellington (allegedly) said, publish and be damned!

 

[ih100]

??????? In light of what you say, how do the majority of OEM's make their machines hang together if they know so little?

 

[tctractors]

I love it, oceanobob and yanky132 great posts, good reading worth a good bit of thought and I thank you for your well put together script, a lot of comments have been posted on welding do's and donts but their is other considerations on the repair of a boom, especialy a small chunk as in the very first post's, the top and bottom plates in boom construction are the main players in copping a load ether upwards or downwards, the side plates or diapham plates (I aint no speller) are usualy a good bit thiner, the scale on torsional loading is 3 to 1, meaning if the top and bottom plates are 3/4" thick, the side plates are 1/4" thick, its all down to a few simple sums to calculate load factor etc, the side walls are often internaly plated with bulkheads to stop compression (pushing out) and tension (stretching) of the side plates, the grade of steel used is the other magic factor, the higher the No like weldox 700 the thinner the steel plates building the boom can be, but the fail point from load stress incorrectly directed is soon found out, if the steel is to tough the fail point is sudden and dramatic, so a ballance between strenght, weight and cost is directed at machinery construction, the little skinny side walls of that Deere boom would be 5mm thick probably, after drilling the crack ends and grooving out the nasty bit (the crack) you would struggle to use the full lenght of a 3.2mm x 350mm welding rod to weld the lenght of it, I dont think any welder would try to use the stump left to try a second pass (fill) so a new rod would be used to do any subsequent passes required, this boom repair is realy about doing a neat tidy workman like repair as the excavator looks in strong nick, then checking other factors to make sure the boom is hoisting level

 

[yank132]

ih100,

Sometimes because Murphy and Mother Nature are asleep at the wheel, rather than conspiring together against us.

Sometimes by ‘overbuilding’ (thereby needlessly stealing natural resources and energy from future generations in the process).

And, in cases like this, by ‘externalizing costs’, and simply letting the end user discover the weakest link.


All component failures can be attributed to 5 overlapping categories:

Design Faults
Manufacturing Errors
Assembly Errors
Inspection/Maintenance Errors/Omissions
Operator Abuse

There is no such thing as a material failure – ALL failures are human in origin.

Heavy manufacturing industries have embraced almost every welding technology that has come down the pike which has been touted as being able to decrease production costs, often for no better reason than to more effectively compete against ‘off-shore’ competitors.

Rarely are the decision makers in these enterprises trained welding engineers.

Process control in most welding establishments in 2012 still involves nothing more than twiddling dials, and listening for the resulting sounds!

The underlying problem is that production decisions are too tightly focused on cost issues, while the engineering solutions require a level of technical understanding and insight that appears sorely lacking.

If you ever have the chance to compare the voltage traces of a pulsed inverter welder and a transformer welder on an oscilloscope you will realize why I, as well as other weldors, contend that the end results (ie. the welds) have inferior fusion and are prone to porosity.

Best regards,

Steve

 

[icestationzebra]

Yank,

That is quite a post.....

Sometimes by ‘overbuilding’
ISZ - I won't say this doesn't happen, but I can tell you of very few instances with the 6 OEMs I have worked for. (I will admit though that most of them were top tier in their markets.) And knowing the amount of engineering Deere and CAT throw at a project I doubt it very much with their products as well. With today's use of computer stress analysis programs this is becoming a thing of the past. If there is overbuilding it is usually done by smaller companies who can't afford to do the computer analysis or they are compensating for operators who do things with the machines they know they are not supposed to. (Don't think we totally ignore all the warranty claims :cool2 ) Overbuilding takes away profit margins, makes the machines harder to ship, reduces lifting/digging capacity, etc.

"And, in cases like this, by ‘externalizing costs’, and simply letting the end user discover the weakest link."
ISZ - Of course we all know that there are numerous humans in the design/manufacturing loop and errors will occur, but the end user will always find the weakest link. If it was designed to never fail you wouldn't be able to afford it and it would be so heavy that it would be uneconomical to operate. The designers are trying to strike a balance between cost, manufacturability, performance, maintenance, reliability and durability. And no you can't get everything so as a consequence different OEMs, or even different product lines, will prioritize different characteristics. And there are definitely some that push short term profits making too far.

"There is no such thing as a material failure – ALL failures are human in origin."
ISZ - Materials do fail. What I think you really mean to say is that material failure is never the root cause. In some way you can always trace it back to human error. I agree with that.

"The inverter based systems used for robotic welding, by design, produce an inherently inferior outcome compared to a traditional transformer based CV power source."
ISZ - I don't have any experience with robotic welders. Are you saying that you can't have a robot use a transformer based power source?

"The last thing any welding operation needs is a MIG welder with a computer!"
ISZ - I don't necessarily agree with this. IF set up properly, and yes that is a big if, a robot is going to make fewer bad welds than a human. My current company, which I can tell you in no uncertain terms takes welding very seriously, is dealing with a lack of qualified welders. Our products do not lend themselves to robots so we have to reach out farther and farther away, but I can see how many companies are driven to robots. Seems there are a lot of younger people who think manual labor is beneath them.

I have an example of doing it wrong. Unbelievable as it may sound, one plant that I used to deal with had welders as the lowest paid job. People walked off the street and became "welders" then moved up to assembly. We had to put 15% more metal in the machines to compensate for the bubble gum welds. One guy missed some welds so he tried using silicon caulk and a quick coat of black paint. For some strange reason the plant was shut down. :beatsme Some of the workers we so pissed off they were throwing bolts across the factory at the managers.

ISZ

 

[RayF]

This boom started off having a small crack and was patched on site. In my experiance most cracks are patched on site and if a spare is available it is changed out soonest and bought back to a large workshop and repaired before it breaks in half like this one did. You can see that a job of this size doesn't lend itself to stick welding.This was welded out with flux core wire and all welds blended,crack checked and the boom stress relieved in an oven before I line bored it. I spent many hours also during the repair running wires and levels to ensure everything was right before it was welded.

 

[ih100]

ih100,

"Sometimes because Murphy and Mother Nature are asleep at the wheel, rather than conspiring together against us."

Can't have it both ways, if it's human error that causes the failures, we'll let human ingenuity have a bit of credit for getting it right.

"Sometimes by ‘overbuilding’ (thereby needlessly stealing natural resources and energy from future generations in the process)."

I can assure you companies like Caterpllar don't put a kilo of steel in un-necessarily. They are constantly looking for ways to reduce material costs.

"And, in cases like this, by ‘externalizing costs’, and simply letting the end user discover the weakest link."

Again, I don't know where you've got facts to back this up, but the largest manufacturers (certainly in the west) spend billions a year in R&D to avoid the end user doing just this. Everyone on here with experience of equipment will know that none of the biggest companies get it right all the time, but if you have any experience of heavy equipment manufacturing you'll know that externalising costs in this way s ultimately counter-productive.


"There is no such thing as a material failure – ALL failures are human in origin."

Covered above.

"Heavy manufacturing industries have embraced almost every welding technology that has come down the pike which has been touted as being able to decrease production costs, often for no better reason than to more effectively compete against ‘off-shore’ competitors."

Against all competitors. Are you saying this isn't a valid reason to cut costs?

"Rarely are the decision makers in these enterprises trained welding engineers."

Bit sweeping. Evidence please, not hearsay, though I'll grant that accountants have too much say in process decisions.

"Process control in most welding establishments in 2012 still involves nothing more than twiddling dials, and listening for the resulting sounds!"

Again, a bit sweeping, but I'm sure you ca back up a statement like this. Fortunately there are a lot of dial-twiddlers who can produce strong, tidy welds that don't fail and can pass X-ray, ultrasonic and every other test you put in front of them. It's an empirical fact that a lot of blue-collar workers don't need nursemaiding by geniuses.


"The underlying problem is that production decisions are too tightly focused on cost issues, while the engineering solutions require a level of technical understanding and insight that appears sorely lacking."

There are a lot of highly qualified and experienced engineers and technicians who would take issue with this statement. I can tell you this from first hand experience.

"If you ever have the chance to compare the voltage traces of a pulsed inverter welder and a transformer welder on an oscilloscope you will realize why I, as well as other weldors, contend that the end results (ie. the welds) have inferior fusion and are prone to porosity."

Sounds a bit like sales talk. Does your company by any chance make transformer-based mig plants?

 

[CRAFT]

..........What I am curious to know is ..... have you fixed the crack yet ??

....... after all guys ..... it's only a ~120 size machine, comparing it to that boom in the above is slightly not the same comparision .... I mean really ! ... that boom not only in all probabilities weighs more than that whole 490D ....the repair is probably gonna cost more than that 490D is currently worth (no insult intended, just reallity) and I'd bet he could buy a replacement boom cheap from Ritchies or ? ...... but that crack is a tell tale in early stages, if it had already opened up I'd see where there is a possability of the boss being cracked all to rat s**t .....

....... since this thread got started I have since talked to my buddy with the Ex 200 (who had the simular cracking problem) and he had just gouged it out with an air-arc to where he had it back to original pin-boss/boom steel, seen no further cracks in the boom metal (he was lucky) re-welded it with a good E7018 stick ..... that was 10yrs ago and it has never re-cracked again ...... no fish plating, no gussets nothing .... just a proper re-weld job and the 200 is really, "twice the machine that this 490 is" ...... I had my 290D for about 5yrs after our simular repair and up to the point of sale also never re-cracked.

But what I just noticed in the side view, is how far up on top of the boom the pin-boss is welded, almost on top of the side plating, almost into the top cord ..... I just looked out the window to my 312 Cat, and seen that the same boss is mounted almost in the middle of the top/bottom cords ? ....huh interesting ! ........... So with that said is it really that smart to suggest a fish plate around the boss that high up to where you are going to be laying a bead into the top cord ???? ..... Just asking the experts of welding out here ...cause if someone told me to do the repair that way I'd be stumped about that ??????? ......

Any ways he's in Alaska and I'd also bet that there some AMAZINGLY great welders around that do this kinda stuff every day........ VERY INTERESTING analagies in the above posts though.....Great reading ! ....... Gitt-er DONE !

 

[Scrub Puller]

Yair . . . I agree with CRAFT, this thread has been a good read, with lots of different viewpoints.

I was the first responder and as you can see from the tone of my reply I did not believe the crack was thad big a deal. Way back I have repared diggers with the full monte . . . gouge out and plate . . . one owner even took the boom off.

It becomes a big job then, sometimes with templates and what all instead of gouge and weld job you can finish infield overnight. Due to time restraints on a couple of jobs I didn't do the plating . . . you know the caper, "we'll do it at the Christmas shutdown". Never happened and the welds in their unpainted glory were there when they traded in the rigs.

As I said in a previous post I think some cracks can provide "stress relief" and I have seen such cracks go unrepared and don't progress for years.

Just some thoughts from an old bush mechanic.

Cheers.

 

[td25c]

From looking at the picture alaska posted we would just air-arc the crack out & weld up as needed ,then see what happens . If the problem continues I would look at fabricating a whole new pin assembly for the boom with an outer pin boss .Most of the older excavators & crane booms were built this way and it worked fine .

 

[yank132]

Icestationzebra, (what a great moniker!)

I’m from the “if a little is good, and a lot is better, then too much is just about right” school of engineering design. Overbuilding is good. Overbuilding works. Overbuilding keeps Murphy from winning too often!

Perhaps the use of CAE & FEA is ‘improving the breed’ across much of the heavy equipment industry. But as an outsider looking in I’m often left to wonder. My concern is that with much better design tools to use, machinery will be built lighter, which will ultimately have an adverse impact 15 years down the road when the 12th owner learns that the broken CAE & FEA optimized boom is too thin/complex to be safely repaired.

Your right, what I meant to convey was that HUMAN ERROR is the root cause of all material failures. Nothing 'just breaks'.

A robotic welder certainly could work with a transformer based power source. But we (ie. society/etc.) seem so much in the thrall of ‘digital’ that anything ‘old skool’ (like a transformer based welder) seems to be viewed as less than worthless (especially by younger people who know of nothing other than 'digital').

Oh yes, robotic welding systems can produce much more consistently uniform results than most/all human weldors can. Setting aside the issue that adopting these machines has displaced countless jobs (which I find hard to ignore), my issue is that the pulsed inverter based technology employed on thick steel sections consistently produces welds that lack fusion and have more porosity.

Rodney Dangerfield’s catchphrase “I don’t get no respect” seems to fit the job title of weldor all too well. In 2007 the average age of a weldor in America was 54! And it’s not much less than that across the whole of the worlds most developed nations. On the bright side, not many young whippersnappers are trying to oust these rapidly aging weldors out of the workforce! Job security at its finest.



ih100,

I originally contributed to this thread to highlight the ‘whys’ behind at least some of the shortcomings with one of the welding processes (ie. MIG) that was being discussed. However, this can’t really be done without going into at least some of the science and physics behind the root issues at play. Evidently my bad for having the audacity to bring this subject to the attention of forum members.

I believe that all the manufacturers of heavy equipment that are using pulsed inverter based welding systems have embraced a demonstrably inferior technology which is contributing to higher costs and is lowering quality. A perfect loose-loose situation for the customer!

And while I realize that perhaps a narrow line needs to be walked in discussing these issues on this forum, welding is an integral technology of almost every piece of heavy equipment in existence. So if the OEM manufacturers are using a welding process to the detriment of the end users best interests (as pulsed inverter welding is) I believe that forum members deserve to be appraised of the potential downsides resulting.

No, I don’t believe that cutting costs by compromising product quality/durability is a remotely appropriate/defensible business decision.

And while your statement that “the largest manufacturers (certainly in the west) spend billions a year in R&D” is certainly true, you don’t have to look very hard to find publications, web forums, law offices, and courts littered with examples of the consumer being screwed/gypped/hoodwinked by some proportion of this expenditure. I thought about using the term 'Ponzi scheme' to describe this situation, but given that Charles Dickens described just such a scheme long before Charles Ponzi became infamous, perhaps the phrase ‘a dickens of a mess’ is more apt.

I know of NO board level 1st tier OEM heavy engineering executives that are trained/qualified welding engineers. Accountants, yes; lawyers, yes; mechanical engineers, yes; chemical engineers, yes. But welding engineers? I can't find a single one!

And yet ALL these firms make products that extensively rely upon MIG welding for their structural integrity and longevity. Go figure.

I didn’t intend to belittle the capabilities of ‘competent’ weldors anywhere (for there certainly are many all over the globe). However, as an industry, welding soldiers on largely in the technological dark ages, where science and physics seems to be viewed with suspicion (or at least apathy) by a significant percentage of welding practitioners and by those responsible for welding equipment purchasing decisions.

My ‘company’ doesn’t manufacturer anything (much less sell welding equipment). Nobody would employ me!

I’m simply someone who, through spending countless hours (pre-internet) in various reference libraries globally, trying to figure out the scientific reason why the same types of welding defects/material failures were showing up in various industries that I was ‘consulting’ for, I hit upon the idea of looking at what was going on electronically while welding by using an oscilloscope. Wow, what an eye opener!

The use of pulsed inverter welders for thick steel is, as Colonel Sherman Tecumseh Potter on MASH was fond of saying, “Horse Puckey!”

Any oscilloscope can show this to be a factually correct statement.

Best regards,

Steve

 

[alaskaforby4]

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