Cracked Boom Pictures! Suggestions? [Archive]

Scrub Puller

03-19-2012, 04:01 AM

Yair ...alaska. If that was my machine I think I would disconnect the rams and withdraw the rods safe from accidental arcs and splatter and maybe undo some brackets and get those hydraulic pipes out of the way.

I'd then gouge or grind the cracks right out and get a full penetration "vertical up" stick weld in there... I am not familiar with that machine and that boss could well be a steel casting so a call to your dealer about recommended rods would be an idea.

The weld needs to be done by a competent operator to get a smooth finish with a bit of reinforce. When finished the bead should be dressed and blended into the surrounding metal with no flaws or undercuts...I generally polish and blend smooth with a sanding disk.

Idealy of course the area should be plated but it becomes a MUCH bigger job. You have to ask yourself how long did it take to get to this stage. The cracks are not that big really and had you not spotted them the machine would probably have worked another season with out any catastrophic failure.

That's what I reckon anyway. . .I'm sure others here will have other valid opinions. All the best with whatever you do.

Cheers.

grandpa

03-19-2012, 07:02 AM

Alaska,,, Scrubs fix is correct,,, but maybe the source of the cracking could be excessive wear between the pin and bearing? I've seen such slop cause exactly what you have there. Maybe check her out, she might be time for a hole build up, line bore and new pin and bearings.... Good luck,

Bluetop Man

03-19-2012, 08:50 AM

How many hours on that machine?

RayF

03-19-2012, 09:29 AM

I don't have a lot of experiance on smaller diggers like that but more on the larger mining excavators.
A crack like that would first be investigated by cutting a window in the boom and the extent of the crack would established.If it goes into the casting (which looks likely) that would be repaired and ground and flushed out.The outside plate would be prepped and a backing plate put on the inside to weld into. Weld out the crack and grind and polish. Then depending on what was found inside regarding the strength of the structure,a ring could be cut to go around the casting and welded in place then the welds blended out. No good going half way with a crack like that. You need to get it fixed right the first time.

alaskaforby4

03-19-2012, 11:55 AM

Ok great, thanks for the ideas

Nige

03-19-2012, 12:20 PM

I'm with Ray on htis one. FFS don't try to "butter this over" by just working from the outside, it will only crack again but 100 times worse the 2nd time. Even though cutting a hole in "good" steel might seem a bit drastic you have to cut a window in the boom so that the inside can be inspected and accessed for welding, repairing cracks in the casting if necessary. You may find that it was a crack in the casting that caused the outside of the boom to crack but you have no idea until you cut a hole in the boom and go looking.

I'd go a bit different to Ray and suggest that if the external boom crack is easily accessible from the inside, then put the backup strip on the outside of the structure and then make the repair weld from the inside. After welding then grind the interior weld smooth and make sure where it transitions to the casting it's well ground to smooth off the radius. Finally the backup strip can then be cut off and the weld can be back-gouged and the final passes made on the outside. Again grind smooth after finishing. Get some preheat in the structure from the get-go to make sure you drive all the moisture out and beat the crap out of every weld pass with a needle gun to stress-relieve it. Possibly add a stiffening plate over the top if it's recommended by the manufacturer. Maybe your Deere dealer can help you, they may have a repair procedure already.

To fix this one correctly is not going to be quick or cheap. If it was me I'd have the boom off the machine so that the repair work didn't have to be done off a ladder. You don't need to make a difficult repair job any harder than it already is.

JDOFMEMI

03-19-2012, 12:35 PM

Well said. The only trouble I see is that being only a 490, the boom is not that big, and inside access may be tough. Just because it is tough, do not skimp on proper proceedure.

It is good to find it now, instead of when it is out on a remote job in poor conditions.

alaskaforby4

03-19-2012, 12:43 PM

Im waiting to hear back from JD on steel type, then we are going to make a decision forward

CRAFT

03-19-2012, 02:34 PM

That's really strange ..... and quite a coincidence ..... that is now the third time i've seen those exact same looking cracks ...... years ago ~'86 I used to rent a JD60D .... Same sort of crack just showed up ..... then I bought an '89 290D, after a couple of years, that identical cracking showed up on it as well "EXACTLY THE SAME PLACE TOO" ........... both of those machines we had the same welder guy just gouge the crap out of it and relay the beads .... they both hung in there for a lot longer than we had the machines.

I wonder if it didn't have something to do with early stages of robotic welding that possibly there was a penetration problem ? ..... just a theory ...... who knows ???? .......cheers

Ps ..... just thinking about this those were Hitachi machines with JD engines in them I just remembered that a buddy of mine has about the same vintage EX200 and he had the same thing happen as well .....Hmmmmmm ????

Scrub Puller

03-19-2012, 03:12 PM

Yair...my theory (for what its worth) is that some tension is built into the structure during initial fabrication and when the cracks occur it provides "stress relief" and in some cases the cracking does not progress much further.

This was the point of my post up-thread. That is to say, rather than going all out for a very expensive full plate and reinforce I would try the gouge and reweld first. I have seen this approach work many times on several applications...notably Allis Chalmers track frames and Kato sticks.

The type of repair done obviously will be influenced by the owners plans for the machine...is it a keeper or will it be traded off down the track a bit.

Cheers.

tctractors

03-20-2012, 04:55 PM

That looks like a little crack on a small excavator, my thoughts would be to just grind out the crack after drilling a small hole at both ends to ease stress, then weld using standard practice Mig or stick weld, this crack could be caused by boom cylinder check valves not setting off equaliy or a bit more greasing to the rod ends? its no big deal, cracks like this are fairly common to find on plenty of booms, if the casting is damaged the cross pin would be cracked, I would not make a big thing out of something so easily corrected

John C.

03-20-2012, 07:38 PM

It was about the time frame of that excavator that Hitachi has similar problems. They repaired the weld as state here but also put a big fish plate on the outside of both sides of the boom. It looked like a big stylized letter H with a hole in the center for the boom pin boss. Hitachi wasn't in bed with Deere in those days so I'm thinking the problem isn't necessarily the same but that big fish plate setup worked just great.

Just a thought.

roadbuilder6

03-20-2012, 09:45 PM

Yikes

icestationzebra

03-20-2012, 11:27 PM

I have worked for several OEMs as a test engineer and have seen this type of crack on other types of machines. My quick diagnosis from your one picture is that the crack started in the middle of the weld closest to the pin. This would indicate that the weld was either not large enough or there is a sub-surface flaw. (It is tough to tell for sure, but I think there is a start/stop point in the middle of the crack) A well designed joint with a good weld should fail at the toe of the weld - where the weld meets the plate.

tctractors "...my thoughts would be to just grind out the crack after drilling a small hole at both ends to ease stress..."
Yes. Just like people used to do with glass, try to drill a hole at the ends of the cracks.

Nige "If it was me I'd have the boom off the machine so that the repair work didn't have to be done off a ladder. You don't need to make a difficult repair job any harder than it already is."
Agree - plus you can flip the part around so you only do horizontal welds which will greatly increase your chances of getting a good weld.

General weld procedure: Scrub Puller has it right. Make sure you have enough heat, clean out ALL slag between passes, and start/stop as far away from the pin as possible. Don't run the welds into the weld between the side plate and top/bottom plate - that would just create a new stress riser in a new location. You may have to preheat the pin boss depending on what material it is.

general comments about patch plates - If you do it wrong you will create a new stress riser and make things worse. If you decide to try this look at what other machines do, or cut out some cardboard of what you are thinking of and post a picture. The same weld procedures apply.

Scrub Puller " ...my theory (for what its worth) is that some tension is built into the structure during initial fabrication and when the cracks occur it provides "stress relief" and in some cases the cracking does not progress much further."
All welding creates built in stress, that is why we see parts warp when they cool. While some cracks may stop or slow down, in most cases though once a crack has started it won't stop until something falls off. FYI - on the very large CAT machines they put the boom into an oven after welding to help relieve the built in stresses.

CRAFT "That's really strange ..... and quite a coincidence ..... that is now the third time i've seen those exact same looking cracks ......"
I'm not surprised. That is one of the most stressed areas on the machine. In "less refined" machines they weld a bunch of different pieces of steel to create the boss, but this leads to a lot of welding and there is bound to be a flaw, which will lead to a crack. A better design is a cast steel boss - you only need one weld joint to attach it to the machine so you minimize flaws, plus the casting is designed to minimize stress concentrations. An even better and more expensive option would be to use a robot to weld this part as it would eliminate 95% of the weld flaws. This machine has one of the first two - not quite sure from the picture.

ISZ

Scrub Puller

03-20-2012, 11:42 PM

Yair...good one ISZ. This discussion here is what this site is all about.

I am pretty much out of the game now but I find it intertesting to come here and and see how other folks (professional folks like yourself, grandpa, Nige and others) deal with problems that us old bushies have been doing our best with for years.

Cheers.

RayF

03-21-2012, 12:27 AM

Back in the days when Komatsu PC650's and PC1000's were a big mining digger we did heaps of cracks in that position. Sometimes the casting inside was so badly cracked inside we either replaced it or fabricated a new one. Casting were hard to get. As said here good weld precedures including correct preheat and we always stress relieved to 580C in an oven after a repair like that. Probably overkill for this job.

tctractors

03-21-2012, 03:22 AM

It is good to see all the differing thoughts and repair methods put forward on the repair of this pin location, it realy makes some interesting reading, the weld area around the boss does look a bit lacking of weld thickness, this is as already stated a common crack zone, I have found the check valves on the hoist cylinders to be a cause of some boom damage through signal pressure imbalance on a few excavators in the past, 1 cylinder would work before the other causing a twisting effort in the boom, I had to replace a few check valves on Volvo excavators with this issue, lets hope the J.D. gets sorted.

RayF

03-21-2012, 04:17 AM

Your right about the check valves. I remember Liebherr having trouble with the early 994's. The cylinders were set up to keep pulling even though the arm was out of travel.A young bloke just out of his apprenticeship used a limit switch wired into the electronics and fixed it.

Nige

03-21-2012, 07:15 AM

What worries me is that there is a casting, 90% or more of which is not visible inside that structure, and if that casting is cracked in a location you can't see I don't care how good the welder is who's doing the repair. It's going to crack again, guaranteed. Repairing the visible cracks just from the outside is chancing it IMHO.

tctractors

03-22-2012, 04:30 PM

Scrub Puller

03-22-2012, 04:55 PM

Yair...hey fellers what am I missing? Comment above from tctractors #18 post.

1 cylinder would work before the other causing a twisting effort in the boom.

When I build stuff with two synchronously working rams I tee between them and feed and return down a common line.

I'm a self taught bush mechanic and (to me) this always seemed the simplest way to balance out the forces and avoid the twisting problem.

What are the disadvantages as obviously (according to the comments) this isn't common practice on diggers.

Cheers.

Nige

03-22-2012, 05:12 PM

Nige, the bit I cannot see I dont think I would worry much about, I would weld it up and check things are working smoooothly, get the pilot to keep his eye on the boom and let it earn a bit of corn??, if it was new I would ask for Product Support to investigate the boom cracks, with a repair or replacement program, but I would not be cutting in to take a peep on a little swinger like this, it might need a plate improvment that often the dealers will have detail information on that might be of help, but hacking holes to get your head in " aint worth nowt" on this chariot.Tony, I take your point. But the problem I have come across many times is that by the time somebody starts to think along the lines of "trying to fix it from the outside ain't working" usually the structure's been so badly buggered about by just welding it from the outside that there's almost nothing left to weld to, and the inside is proably in pieces. I know it's easy for me to say "fix it once, fix it right" because my previous experience has taught me that a large percentage of structures like this boom can generally only be successfully welded as a long-term fix by going inside and sorting out the problems there first instead of going for the quick fix and just welding the outside.

I understand your point completely about getting the machine up & running and earning, but you and I both know from past experience that today's "temporary" fix has a habit of becoming permanent and is possibly only putting off until tomorrow what should really have been done today and if it had been it would have only taken half the time if someone had bit the bullet and done it right first time.

Like you I would be looking to the manufacturer's dealer network in the first instance to help with a repair procedure before even starting to clean the paint off the cracks. It would surprise me very much if they didn't have something.

I can also understand why people who haven't previously seen repairs done by cutting holes in a structure being more than a bit wary of the procedure, but in truth it's really quite simple, and what's more it works. What I'm going on for this excavator is a load of documents I have for similar size Cat machines detailing repair methods for booms that in all probability are dam nigh identical in internal & external design even though they are painted a slightly different shade of yellow.

alaskaforby4

03-22-2012, 10:21 PM

The cracks will be drilled, v'd welded, ground smooth and a 1/2 plate is going around the pin boss and everthing from the top to the bottom, I'll post pics once we get it finished.

r_steven

03-22-2012, 10:29 PM

I know I'm coming in a bit late, but couldn't a hole be drilled into the boom and an inspection camera be used?

tctractors

03-23-2012, 03:24 AM

Scrub Puller, the common practice on excavator hoist cylinders is the fitment of check valves, these are often signal pressure activated to put the boom rams to move, there is also the fact that each cylinder has its own check valve set, so if 1 cylinder valve is releasing before the other due to valve adjustment etc, the boom cylinders are working on the gimp so as to speak, I check the signal line pressure with the boom up, engine stopped, pressure gauges on both check valves, then lower boom using stored hydraulic power to lower, 1 check valve will always open before the other, it just needs to be a close thing, I myself think check valves are a pain, slowing the working rate of a swinger a good bit, but they must have saved a few lifes plus they are hear to stay so its "bend with the flow"

Scrub Puller

03-23-2012, 06:39 AM

Yair...gotcha tctractors. Thanks for the explanation.

Cheers.

Nige

03-23-2012, 07:58 AM

The cracks will be drilled, v'd welded, ground smooth and a 1/2 plate is going around the pin boss and everthing from the top to the bottom, I'll post pics once we get it finished.If you like PM me with an e-mail address and I'll send you a repair procedure for a Cat boom of similar size. It might give you a few pointers, especially regarding the shape and the welding sequence of the reinforcing plates.

I know I'm coming in a bit late, but couldn't a hole be drilled into the boom and an inspection camera be used?Good point, never thought of that. Especially with modern fibre optics to light up the inside.

uffex

03-23-2012, 02:12 PM

Good day cracked JD
My experience of the cracks in this area are caused by a inbalance in the hoist cylinders very common when the boom cylinders are fitted with hose failure valves. I recommend you check out the cylinders a issue much the same was recorded by www.excatech.com some time ago, I hope this helps if not you can mail me for more details.
KR

tctractors

03-23-2012, 02:45 PM

Nige on a light note, I never worry about my customers equipment, I only worry about how they intend to pay my bill, for years I have been focused on doing a good job, doing the impossible with little reward and never any thanks, in these tough times the machine owners only want them earning coins, so a crack in a light excavator boom would be drilled, welded and plated in as fast as my backside could be kicked, I might be able to get a days work out of it, but it would not be 2, this week I had to be on a site Wednesday morning at 6.30am to fix a Volvo dumper near Hereford, just as I was thowing my tools in my chariot I get a call to go to J10 of the M40 to repair a broken track on a Rock Hawg, by the time I finished pressing up the pins etc and made it home it was 1.30 am, the Volvo owner will take forever to pay up and I would be suprised if the Rock Hawg man beats him on the coin sorting deal, so thats why I dont worry about if things brake in 6 months time. blowing it on tctractors

Scrub Puller

03-23-2012, 03:39 PM

Yair...I know the feeling tc...see my comment on "reasonable charge for repair thread".

It's not funny but it makes you laugh.

Cheers.

rare ss

03-25-2012, 05:45 AM

worse i had was a CAT 235C which had cracked through 3 sides (bottem was holding the boom together) and the top had opened up enough to fit your hand inside the boom, funny thing was the operator was still loading trucks!

will have to find some pics, we just scrapped the boom, found another one which was differant prefix had to re-bend/remount pipes and fit sleaves in the lift ram bores, was a fun time

pp13bnos

03-25-2012, 04:37 PM

He just wanted to get every ounce of $$ out of the machine. ;) Pics would be great though.

oceanobob

03-25-2012, 09:46 PM

Should the weld rod be 7018 or perhaps one of the so called 'repair weld rods' which have additional ductility and perhaps a bit more strength? I use the 7018 fresh out of an oven but the sales approach of the 'repair weld rod' I always wonder about.

tctractors

03-26-2012, 03:35 PM

Nige

03-26-2012, 03:53 PM

We came across some extremely useful rods for repair welding - Eutectic Xuper Nucleotec 2222. Originally designed for the nuclear power industry. Much more ductile than a 7018 (45% elongation) but with almost identical tensile properties.

Karl Robbers

03-27-2012, 06:47 AM

The weld could be 7016 - 7018 or MIG, that is low Hydrogen basic coated welding rods would give the best result, there is talk of pre heat etc, but I would glue it all up with 7016 3.2 rods at the correct voltage and forget the heat, but that is me doing a job and we all do things different???, any plate aditions would be welded in the same style if possible using weldox plate or 50b grade steel, then I would check out the hoist ram set up for even operation as something has caused this crack to show its face, but its a common crack to see, it also gets fixed easy.
Don't mig it whatever you do!
Solid wire mig is a low hydrogen process for sure, BUT, it has nowhere near the toughness of a 7018 electrode, particularly when an Argon based shielding gas is used. If we are talking FCAW, (flux core arc welding) then that is equal to or better than the low hydrogen electrode.
As to preheat, when in doubt preheat. When the grade of steel is unknown, particularly when dealing with heavy or uneven thicknesses preheat is a must as it reduces thermal shock, slows cooling and also has the ability to drive out moisture from the joint, all of which contribute to a sound weld.
By preheat we are talking between 50 to 200 degrees celsius.
When welding the joint full penetration is imperative and don't just chip the slag out - give it a light grind every run, make sure that your finished weld has no undercut and is not overfilled as this creates stress at the toe of the weld. Obviously cool as slowly as possible, (don't quench and try to avoid cold winds etc).
Personally, I would use a 3.2mm (10ga) 7018 electrode (due to their smoother running and better deposition rate over the 7016) although for the root ron may opt for the same electrode but the next size down if I felt I needed more control over penetration/ blowthrough.
Generally speaking, for repair work the low hydrogen stick is king.

Nige

03-27-2012, 07:43 AM

tctractors

03-27-2012, 01:49 PM

Just like to say I used to do pressurized welding (pipe Line) but now only certified for upto 2" vertical permenent work, my welding skill and prefered method is MMA, the MIG weld is avoided by myself as much as possible, low hydrogen welding rod (Basic coated) are to all intents just sand coated (silica) after welding the slag is like glass and can be hard to chip off/remove, all that grinding and needle gunning is great, but making sure the W/Rods are dried as specified on the box to reduce the Hydrogen parts per Million is the route to go, 7016-7018 are both great spec rods for this style of repair, anything is better than a crack some times

Nige

03-27-2012, 02:01 PM

Needle gunning is a must for stress relief - it has an additional advantage that it cleans the slag off the weld at the same time. Can't argue about making sure the rods are dry, expecially in the climate condtions here where it seems so rain 330 days a year.

oceanobob

03-27-2012, 02:59 PM

.
... 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

03-27-2012, 03:37 PM

.

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

03-27-2012, 04:14 PM

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

03-27-2012, 04:48 PM

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

03-28-2012, 04:32 AM

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

03-28-2012, 08:23 AM

Karl Robbers

03-28-2012, 05:58 PM

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

03-29-2012, 11:40 PM

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

03-30-2012, 02:04 AM

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

03-30-2012, 09:55 AM

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

tctractors

03-30-2012, 03:47 PM

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

03-30-2012, 05:23 PM

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

03-30-2012, 10:29 PM

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

03-31-2012, 06:48 AM

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

03-31-2012, 12:03 PM

[QUOTE=yank132;350131]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

03-31-2012, 12:05 PM

..........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

03-31-2012, 03:33 PM

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

03-31-2012, 10:17 PM

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

04-01-2012, 01:04 AM

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

04-07-2012, 11:39 PM

The Fix

pp13bnos

04-07-2012, 11:46 PM

Looks good to me!

John C.

04-07-2012, 11:57 PM

That is about what the old Hitachi fix was years ago. I would be really surprised if the crack ever shows up again.

Really nice work!

JDOFMEMI

04-08-2012, 12:12 AM

Nice work! That should hold for a good long while.

ddigger

04-08-2012, 12:16 AM

well done

Scrub Puller

04-08-2012, 01:28 AM

Yair . . . yank132 Thanks for the detailed post.

For this old bush mechanic some things are slipping into place. As mentioned up thread I see things break from the OEM and I rock up with the old Lincoln with a couple of packets of low hydrogen sitting on the exhaust manifold of the Perkins and I gouge it it out and weld it . . . no plates or anything and it never breaks again.

I have no confidence in any weld made by a wire feeder on anything over three eighth . . . might look okay on the surface but so do some bad women.

With the inverter power sources for TIG though I reckon they are magic. . . especialy for alluminium.

Any comment?

Cheers.

OldandWorn

04-08-2012, 07:17 AM

Good looking repair alaskaforby4. I would also like to comment on your nice shop and well maintained looking excavator. Is the red thing in the corner a press?

Nige

04-08-2012, 11:08 AM

I think that repair is going to solve the problem, however I'm going to be picky and opine that maybe the curves should have been "tailed out" even more pronounced than they have been and maybe that the welding on the curves should have stopped possibly an inch before the end of the plate rather than run right to the end (and into the high stress areas of the top/bottom plates) as they have been. But as I say that's me being picky.

I like the fact that the repair has been cleaned up and painted afterwards. Proves my theory about "if it looks professional, it's likely to be professional"

alaskaforby4

04-08-2012, 11:37 AM

Thanks! Yes its a 50ton press, she is an antique but it works great!

icestationzebra

04-16-2012, 02:38 AM

robin yates uk

04-16-2012, 03:43 AM

that repair will outlast the pyramids, good luck

Nige

04-16-2012, 09:30 AM

The patch looks pretty good. The rosette welds are a good touch. The only thing to watch it that new cracks don't start forming at the corners of your patch plates, especially since they end in line with the stick cylinder anchor. I think you will be OK, but it would have been cheap insurance to run the corners out farther.

ISZGlad that it wasn't just me who was thinking about curving the doubler plate more & tailing the welds out. I always believed that you need to "curve & tail" the doubler plate out so much that the weld on it is almost running parallel to and about 1" away from the OEM weld at the point at which it runs off the plate. The plug welds in the holes on the repair are perfect so that the stress created by welding the fillet welds at the edges of the plate do not tend to pull the centre of the plate up away from the structure.

Please don't take what I have written above as a criticism. I reckon that repair will outlast the machine. :drinkup

TozziWelding

04-16-2012, 03:10 PM

Looks good, but I would have rounded the corners on the patch, cracks propagate at sharp corners.
90094

xcmark

04-16-2012, 04:06 PM

Looks good, but I would have rounded the corners on the patch, cracks propagate at sharp corners.
90094

I think if I was going to own this machine for a long time I would plate the other side of the boom the exact same way , chances are if one side is stress cracked the other is not far behind.

well done.

CRAFT

04-16-2012, 04:23 PM

I think if I was going to own this machine for a long time I would plate the other side of the boom the exact same way , chances are if one side is stress cracked the other is not far behind.

well done.

If you go back and look at all the pics he submitted you'll see that he already did : Post #1- shows that the original crack was on the right side of the boom .... Post #60- (1st pic) shows the right side preped for the new plate and a repair weld ...... and the last pics just happened to show the repair completed on the left side of the boom .... just thought i'd bring that to your attention .... :drinkup cheers

Nige

04-16-2012, 06:03 PM

Looks good, but I would have rounded the corners on the patch, cracks propagate at sharp corners.

Sorry I don't agree. IMO the doubler plate needs to be curved outward like this illustration. Also the doubler plate need to be approximately 30mm (1-1/4") narrower than the structure - 15mm on each side. The welds on the curved ends of the doubler plate should either stop about 20mm (3/4") before the end of the plate, OR be run out 50-75mm (2-3") past the end of the plate terminating parallel to the existing structural welds and approximately 15mm away from them

90095

Bluetop Man

04-16-2012, 06:30 PM

welds on the curved ends of the doubler plate should...stop about 20mm (3/4") before the end of the plate

I've noticed this technique is a prevalent practice in the fabrication of CAT equipment with welded attachments.

I don't have a clue as to how the off brand manufacturers do it...:beatsme

icestationzebra

04-17-2012, 12:32 AM

Sorry I don't agree. IMO the doubler plate needs to be curved outward like this illustration. Also the doubler plate need to be approximately 30mm (1-1/4") narrower than the structure - 15mm on each side. The welds on the curved ends of the doubler plate should either stop about 20mm (3/4") before the end of the plate, OR be run out 50-75mm (2-3") past the end of the plate terminating parallel to the existing structural welds and approximately 15mm away from them

90095

Nige - If you are referencing the picture you attached, the doubler plate is narrower so that the weld beads line up with the side plates to get the most strength. Plus if you run too close to the edge you risk a burn out which will create a big stress riser.

"that repair will outlast the pyramids"
This repair looks pretty solid, but one thing that I learned early on is that adding metal is not always the answer. Often you just move the problem somewhere else! And the welding details (filler, preheat, fillet size, post treatment grinding/peening, etc.) are just as important. Every place in a weldment where you have a change in shape or thickness is an increased risk of cracking. If you want proof just compare the shape of almost any machine today vs. it's 1970's counterpart. Even though it is more expensive you now see mostly radiused or tapered parts vs. the old boxy shapes.

Anyway, just tryin' to pass along some wisdom. Hopefully it helps someone else. :)

ISZ