Repairing Tilt Lever Failure in Loaders: Is Welding a Viable Solution?

[Welder Dave]

In order for Cat to have any kind of quality control they need to know the make up of their cast and forged parts (all metal parts for that matter). Nige has access to that information. Cat also has repair procedures and needs to know so that proper filler metals and welding procedures can be followed.

 

[DDoug]

Reverse engineer a new one made from a fabrication.

 

[Welder Dave]

Not always easy to fabricate a replacement for a casting or forging.

 

[mdrifki]

I have my sources and I would guarantee their accuracy.

Thank you, Nige, for your expertise. I hope you can help me again in the future.

 

[mdrifki]

You got this info from Cat therefore I assume the machine is an Elphinstone underground loader. Is that correct.? Do you have the OEM Part Number for the tilt lever.?

I've never heard of "MS025". Cat Material Codes are generally in the format 1Exxxx, colloquially referred to as the "1E Number". Believe it or not but there are two 1E Numbers right there in the photo, plus a Date Code of 07/02/2022 if I am reading it correctly. I assume that was the date of manufacture of the part.

EDIT: 1E1123 is cast steel - 0.17-0.19% carbon.

Bearing in mind the location of the structural failure of the tilt lever in my opinion there are two chances of you being able to successfully repair it by welding - slim and none.


Every tilt lever I have come across on Cat equipment has either been cast steel or some type of fabrication. From the photos the OP's lever is obviously not fabricated so ergo it's cast.

Before attempting any sort of "repair or replacement" decision I would suggest a close look at the operating techniques because, again in my experience, tilt lever failures of any type are a direct result of poor operating practices. Especially repeated banging of the tilt lever against the stops while dumping the bucket.

Hai Nige, do you know material that equivalent with Steel(1E4377A)?

 

[Nige]

Sorry I have no idea.

 

[Welder Dave]

Are you still considering welding it?

 

[sawmilleng]

mdrfki,
Have you considered comparing the cost of weld repairing a broken lever to fabricating a replacement lever? I'm not just suggesting a simple design process, but actually having an engineering company that is expert in finite element design have a look at the forces that are seen in the lever and design a welded fabrication that accepts these forces?

I would think that once the lever is properly modelled in FEA the design of a replacement lever can be relatively straightforward. The analysis should show up reasons why the cast levers are failing. You may find that a welded fabrication may be quite a bit less costly and may easily made stronger in the areas that need the strength.

Just because Cat had originally designed the lever to be a cast steel article does not necessarily mean that they spent the effort to computer model the component to make sure that it was the best design. If a few break in service, well, the parts department makes a bunch of money by selling replacements. And it seems that the replacements are pretty pricey compared to what a fabricated part might cost.

Jon.

 

[RayF]

Those Elphinstone levers are cast in a better grade than mild steel. I have worked on them and they can be done if a weld procedure is followed. The break needs to be properly prepped and any oxy cutting ground away a good millimetre to get under the heat affected zone. Preheat and tack together. Put run off pieces on for the welding. Keep the heat up to 250C while welding with a S6 wire. Don't be tempted to use a Hi Tensile wire as this will cause a brittle fusion zone. Won't hurt to peen during the welding. Preferably, without letting it cool out, get it into a heat treatment oven at 580C for around 4 hours.
When line boring there needs to be a precut before welding,about 3mm oversize and a preheat before welding. I have repaired several where the precut wasn't done and it's easy to see that the final cut was done in the fusion zone and has cracked.

 

[Welder Dave]

I wouldn't use solid wire Mig unless it was in spray arc mode at high amps. Short circuit Mig just doesn't have the penetration or enough heat input for the thickness of the steel. Dual-shield flux-core would be preferred if a faster process than stick was desired. Something equivelant to 8018(8018C3) with 1% nickel would give better mechanical properties than a 7018 equivelant and the 1% nickel would give added toughness without making it brittle. Have never heard of HAZ issues from cutting but the cuts would need to be ground and preheated and stress relieved after welding. Preheat, interpass and post heat/stress relieving would be critical for a successful repair. Stress relieve may need to be higher than 580C and up to 650C. It would also have to be gradually slow cooled over a few hours. I would think a shop that specializes in stress relieving would know all the pertinent info. It's something you want done by people fully experienced in stress relieving. A large vessel shop (Dacro Industries) not too far from me has the largest stress relieving oven in N. America, 36'x36'x156'. They're the same shop that built the 820 tonne vessel longer than a football field that was trucked to the final site. Pretty impressive move. There's a good video of the move and the stress relieving oven is in the background at the beginning.

 

[nicky 68a]

Just found this thread.
We have one of these machines currently for sale.It’s certainly built very well and is impressive to look at.
I guess it’s around the Cat 980/988 sort of size as it has a C18 motor stuffed into it

 

[mdrifki]

Those Elphinstone levers are cast in a better grade than mild steel. I have worked on them and they can be done if a weld procedure is followed. The break needs to be properly prepped and any oxy cutting ground away a good millimetre to get under the heat affected zone. Preheat and tack together. Put run off pieces on for the welding. Keep the heat up to 250C while welding with a S6 wire. Don't be tempted to use a Hi Tensile wire as this will cause a brittle fusion zone. Won't hurt to peen during the welding. Preferably, without letting it cool out, get it into a heat treatment oven at 580C for around 4 hours.
When line boring there needs to be a precut before welding,about 3mm oversize and a preheat before welding. I have repaired several where the precut wasn't done and it's easy to see that the final cut was done in the fusion zone and has cracked.

Hello RayF,
Thank you for your response and valuable suggestions.
May I ask how long your repair lasted in service?

I recently repaired one of these parts. The initial crack was about 7 mm deep. I did not perform a PWHT, but the part passed NDT inspection. However, after being put into operation, a new crack developed on the opposite side of the component — away from the original repair area.

What do you think could have caused this?
Could the absence of PWHT have contributed to the failure?

 

[DDoug]

mdrfki,
Have you considered comparing the cost of weld repairing a broken lever to fabricating a replacement lever? I'm not just suggesting a simple design process, but actually having an engineering company that is expert in finite element design have a look at the forces that are seen in the lever and design a welded fabrication that accepts these forces?

I would think that once the lever is properly modelled in FEA the design of a replacement lever can be relatively straightforward. The analysis should show up reasons why the cast levers are failing. You may find that a welded fabrication may be quite a bit less costly and may easily made stronger in the areas that need the strength.

Just because Cat had originally designed the lever to be a cast steel article does not necessarily mean that they spent the effort to computer model the component to make sure that it was the best design. If a few break in service, well, the parts department makes a bunch of money by selling replacements. And it seems that the replacements are pretty pricey compared to what a fabricated part might cost.

Jon.

We sometimes convert from a weldment to a casting for items cracking
under stress.
Most everything get's run thru FEA these days, even Inventor CAD running
on a PC can do it.

 

[Welder Dave]

Lack of PWHT/ stress relieving could definitely be the cause a new crack(s) to develop. It's one of those weldments that the proper repair procedure has to be followed to a T! A sound weld is only one of the requirements. Proper filler metal, preheat, interpass and post weld heat treatment are all equally important.