Frame break Komatsu PC 110R

[cat951b]

Hey guys!
I would like to ask for help with a Komatsu PC 110 R frame break. I've heard that this is a common fault with these machines, but I couldn't find any information about it online. Has anyone had a similar problem or experience with this? I'll try to take photos of it tomorrow. The "Y" frame supporting the boom is broken under the cab and the fuel tank. I bought the machine a few days ago at a good price and it is in pretty good condition. Any little help or information can be useful, thanks in advance!
Zsolt from Hungary.

 

[cat951b]

Hi everyone.
I started to disassemble the machine to get access to the broken frame..

 

[Lagwagon]

If your an experienced welder then you know what to do, if your not, get an experienced welder. This is not an easy job and if not done correctly will likely break again and be harder to fix.

 

[Welder Dave]

Yeah, that's a pretty big repair job. Not a DIY job unless you have a lot of welding experience. First thing you need to do is get all the hoses and wires well out of the way. You may have to dismantle part of the machine to have enough room to do the welding. May help to drill holes at the ends of the crack. Everything will have to be beveled for full penetration welds or a section cut out so an inner backing plate could be inside and then filled up with weld. It also looks like the wide part of the crack needs to be pushed together. The problem there is if it's pushed together and welded there will be a big stress build up because the weld won't be able to contract naturally when cooling off. You'd need to stress relief it to get the best strength. Preheat and peening every pass will help along with post heat and slow cooling with a welding blanket or some kind of insulation. You could put some reinforcing plates on but make them oval and don't weld all around the ends. It would be good idea to drill a hole or leave a small section unwelded if the assembly is boxed in. This will stop the heat from welding building pressure inside. Let it mostly cool off and then weld the hole or finish the weld. The pressure build up inside a smaller box section can be enough to cause the weld to crack as the pressure is trying to escape. I'm not sure if the entire broke section could somehow be removed? It would certainly make it a whole lot easier. It's a big repair and not worth doing unless you try to do it as well as possible.

 

[cat951b]

Hello Lagwagon, Hello Dave,
Thanks for the info and advice. I appreciate! Yes, I have experience in this field and can also weld. I also have tools. I am not saying that I am the master of such repairs, but I judge myself that it will work. Of course, more specialists and more experience can always be a good help.
Of course, I will share more photos of the work process with you.
Dave, I see you have a lot of experience in this field, can I contact you in a private message to analyze a detail or two?

 

[Welder Dave]

Just ask on the forum. It's a big repair so there are no dumb questions. There might be good ideas from others. You can PM me if you'd like though. I will say you need to use 7018 electrodes or an equivelant to do the welding. I know 6013 is common in Europe but it is not suitable for this type of repair. I'm just posting established good welding practices. A needle scaler or even a dull chipping chipping hammer to peen the welds while hot would help relive some stresses.

 

[cat951b]

Just ask on the forum. It's a big repair so there are no dumb questions. There might be good ideas from others. You can PM me if you'd like though. I will say you need to use 7018 electrodes or an equivelant to do the welding. I know 6013 is common in Europe but it is not suitable for this type of repair. I'm just posting established good welding practices. A needle scaler or even a dull chipping chipping hammer to peen the welds while hot would help relive some stresses.

Hello Dawe, ok.

Unfortunately, I do not speak English and I use the Google translator for communication, which does not always give a clear translation. That is why I may ask you several times about the same topic, so I ask for your understanding and patience. Thanks.

 

[cat951b]

Thank you for your advice regarding the preparations, (dismantling, grinding, preheating, slow cooling...) this is fine. I have a personal relationship with a welding shop, where they help me choose the right welding rod. For me, what is still not clear is the stress relief after welding, could you explain the technique of this in more detail? I would like to repair the broken frame with an "X" welding seam, and then strengthen it on both sides with webbing. (See photos) what do you think about this?

 

[The Peej]

I don't think you need to apologize for not speaking English anymore than we need to apologize for not speaking your language.

I will probably never be involved attempting a repair like this but still like to hear about it and learn the process.

 

[Welder Dave]

I don't think you could do a double bevel X style set up. You can't weld from the inside. You need to do single bevels from the outside to get 100% penetration or leave a gap where you can fit a backing plate inside. Don't need to worry about U groove. U grooves are used on thick vessels/plates to reduce the amount of filler metal required. You just want a good sound weld. The heat from welding and then cooling can create a lot of stress in the metal. Stress relieving gets rid of that stress. It's done on large excavator booms, dragline booms, critical pressure vessels and pipe and other weldments. The steel around the weld including the welded area is heated to a specific high temperature and then carefully slow cooled. Large furnace rooms or induction heating blankets are used. I think the temp. for steel is 1400- 1650F deg's. but would have to look it up. I'm not sure if you'd really need it if you peened the welds and slow cooled them.

 

[cat951b]

A few photos of the demolition process...

 

[cat951b]

...

 

[oarwhat]

Is the broken piece solid? or hollow?

 

[cat951b]

Is the broken piece solid? or hollow?

Solid.

 

[Welder Dave]

I thought there was a boxed in section. Now I'm thinking the cracks are a result of bad steel or fabrication techniques. Maybe wasn't preheated and crack started in heat affected zone of weld. I can't see the pics. good enough on my phone. I'll look on the computer when I get home. Is the crack(s) anywhere close to the edge of a weld?

 

[cat951b]

Fortunately, there is no box, by removing the cab you can easily access it from all sides. I also thought a lot about what could have caused this break?! The machine is 15 years old and has 8,100 working hours and is in very good condition. It was owned and operated by the same person. (unfortunately, I didn't know him) If it was a material defect, it should have broken already. There are no signs of excessive force on the devices that come with it. Yes, the cracks start at the end of the stiffener plates. Material size 40x250mm (1.6"x10")

 

[cat951b]

Now I'm thinking the cracks are a result of bad steel or fabrication techniques. Maybe wasn't preheated and crack started in heat affected zone of weld.

I don't think the entire frame is preheated before welding during series production. It was produced in northern Italy and it is possible that the production took place in the colder winter period when the raw material was colder and the welding cooled down faster?!

 

[HarleyHappy]

Was a hydraulic hammer run on that machine? That is just plate steel and yes the gussets, where they end is what killed it.
That or it was rolled off a trailer.
Not to hard to X weld that and add in some strengthening plates on both sides, well past that brace, only need room for the pump.
Not really into the turn table.
Those welds were done with high nickel sub arc welding. I would root pass with a mig and stick weld from there making sure to rotate sides to keep an even temp and cover as it cools. Peening will help.
Whatever you do, don’t let it cool off fast.

 

[Welder Dave]

The heat from welding the stiffener plates could have contributed to the cracking. It's not a big excavator so it's doubtful if any special welding procedures or higher nickel filler metals would have been used. Likely no preheat either which may have prevented the failure, especially if the weld on the stiffener started at the same place the crack started. Instant quenching effect. Even slight undercut from the weld on the stiffener could be where the crack started. It may even be case where the end of stiffener would have been better left un-welded. The same reason you don't typically weld across the boom on excavators. I don't know if the steel was cut from plate or was made as a long bar. Bar stock typically has the grain structure going lengthwise where plate has the grain structure going in multiple directions. Basically if pieces are cut from plate they will have equal strength no matter what position they are placed in. Pieces cut from flat bar only have max. strength in the direction of the grain structure. For a lot of stuff it won't matter but will on more critical weldments. Preheat before starting the repair.