Komatsu pc200-7 swing pinion shaft broke

[GTpesado]

what would make this komatsu pc200-7 pinion snap off like this???
I changed the oil seal about 2 years and 2,000 hrs ago. I had to change the bearings because they were seized onto the shaft and i could not press them out

 

[Simon C]

It must of had a hair line crack or the house came to a sudden stop while swinging and the weakest link broke.
Simon C

 

[John C.]

When you changed the bearings back when you changed the seal, how did you remove the old ones from the shaft? You can see the beach marks indicating a progressive failure. There is a flaw in the gear side of the shaft at the lower right corner. That can be caused by an inclusion in the shaft material when manufactured or it can be as simple as a punch or chisel dent from removing the old bearing.

 

[GTpesado]

I pressed the pinion out of the top bearing with about 60 tons of pressure . But the bottom one I took up to 150 tons and it did not budge so i cut it off….the pinion was in perfect condition with only a little wear in the teeth….but no nicks or dents. I put a bucket of amber grease in and i dont think the customer checked the grease in the 2 yrs that he ran it. It seems pretty dry in there i guess that could have made it worse?…..its not like i change these everyday…and i was just wondering if i could have possibly stressed it or is there something that i should have done diferrently?

 

[Nige]

the pinion was in perfect condition with only a little wear in the teeth

But what was the condition of the pinion shaft right where the bearing mounts.? Is there any chance it was nicked even by a hair when the old bearing was removed.? I’m assuming the bearing that is still on the pinion in your photo is the one you had to cut off 2 years ago.?

How were the replacement bearings installed.? Pressed on or heated.?

 

[Coaldust]

I think it had a stress riser from the bearing removal. Beach marks. That happened over a period of time, before the final fracture.

 

[Welder Dave]

How was the excavator being used? I know with a wrecking ball you should never swing it using swing, only use the stick. I think trying to push too much material using swing or slamming into a pile is also hard on the swing gear. It kind of looks like the shaft sheared and then finally broke.

 

[Coaldust]

The swing circuit line relief valves should protect the gear from abuse, unless the pressures are jacked.

 

[Welder Dave]

In normal operation relief valves work but the swing gear can still be abused. Relief valves don't help if you do something stupid like repeatedly slamming the bucket into something solid.

 

[BC Placer gold]

^^^^Have seen operators that make up for a lack of skill/proper technique use side 'sweeping' as a matter of course....

Won't name 'names' but (my buddy) is guilty of this, have seen him trying to side push large trees or piles of dirt...just a matter of time until failure/severe damage. Won't let him on our machines...

 

[GTpesado]

But what was the condition of the pinion shaft right where the bearing mounts.? Is there any chance it was nicked even by a hair when the old bearing was removed.? I’m assuming the bearing that is still on the pinion in your photo is the one you had to cut off 2 years ago.?

How were the replacement bearings installed.? Pressed on or heated.?

I think what you are seeing is where the seal runs ….here are some closer pictures. When i cut the first bearing off, it looked like moisture had gotten between the pinion and bearing race, because it was like seized or rusted to each other. Some of the nicks and busted teeth i am sure occured after i broke because the operator tried to straighten it out to load it on the low boy.

 

[GTpesado]

what would make this komatsu pc200-7 pinion snap off like this???
I changed the oil seal about 2 years and 2,000 hrs ago. I had to change the bearings because they were seized onto the shaft and i could not press them out

Thanks for you guys thoughts on the matter, my guess is it was some abuse and mabey some stress and wear from the last time we had it out

 

[GTpesado]

I see some options for some generic pinions ?? Are they worth sticking in? Or is it better to go with 5k option from komatsu? Thats just the pinion plus seals and bearings

 

[Martin70]

I see some options for some generic pinions ?? Are they worth sticking in? Or is it better to go with 5k option from komatsu? Thats just the pinion plus seals and bearings

I used a generic in a cat, that was many years ago, still going without issue. Trying to remember the brand name, but can't.

 

[Nige]

I think what you are seeing is where the seal runs ….here are some closer pictures. When i cut the first bearing off, it looked like moisture had gotten between the pinion and bearing race, because it was like seized or rusted to each other. Some of the nicks and busted teeth i am sure occured after i broke because the operator tried to straighten it out to load it on the low boy.

I’d still be interested to hear how the new bearings were installed, heat (bearing heater or boiled in oil) or a press.

Does the seal run on a smaller diameter than the bearing and just above it.?

 

[Welder Dave]

Thanks for you guys thoughts on the matter, my guess is it was some abuse and mabey some stress and wear from the last time we had it out

Do you know how the machine was being used when it broke? You haven't said anything that might help reveal why it broke. Not saying it was abused but sometimes people don't want to admit they did something wrong that caused damage.

 

[John C.]

I have rebuilt several of the older Dash series machine swing boxes on multiple sizes of excavators and can say that it is normal to cut the old bottom bearing off with a cutting torch, I have never seen a failure on a pinion shaft that could be attributed to the use of the torch.
The only ways a swing pinion and swing box can be abused is if the swing parking brake is engaged and the boom has something hit it with a lot of force. Think about a dozer running into the boom at speed while the machine is parked or the machine is tied onto a trailer for transport and the machine hits a bridge. The other way to abuse the swing box is running the machine with no oil in the gear box or never changing it when called for in the manufacturers recommended interval. Not enough grease in the ring gear tub causes sliding wear on the pinion more than on the ring gear and that wear can be felt as back lash between the house and carbody. I have done inspecting on many excavators that have never had the grease in the tub checked and even had sand and mud packing in them and all it did was put that sliding wear on the pinion. Your photo shows some wear on the teeth of the pinion but whether it is abnormal would depend on the total amount of hours on the component. The damage on the pinion tooth in my opinion as observed from the photo is from some foreign object being pinched between the tooth and something else. Is there matching damage to the case?
On the second set of photos I see the broken inner race on the broken bearing and all the damage to the mounting area on the pinion. I just note it because there isn't any use in speculating about what happened.
I would not have any problem with an aftermarket pinion and sourcing bearings through a bearing house. I always sourced the seals from the dealer.

 

[GTpesado]

I’d still be interested to hear how the new bearings were installed, heat (bearing heater or boiled in oil) or a press.

Does the seal run on a smaller diameter than the bearing and just above it.?

I just pressed the new ones on. They went on fairly easy with out to much pressure. Both bearings have a plastic ring in them….can you heat them??

 

[GTpesado]

Do you know how the machine was being used when it broke? You haven't said anything that might help reveal why it broke. Not saying it was abused but sometimes people don't want to admit they did something wrong that caused damage.

yes this is the big question…. It’s a customers machine, and his operator is not real experienced… he was loading trucks i a narrow cut he was making and i can easy see him catching the top of the bank on his way around!! Of course he never said anything about that…it just stopped swinging !!!

 

[GTpesado]

I have rebuilt several of the older Dash series machine swing boxes on multiple sizes of excavators and can say that it is normal to cut the old bottom bearing off with a cutting torch, I have never seen a failure on a pinion shaft that could be attributed to the use of the torch.
The only ways a swing pinion and swing box can be abused is if the swing parking brake is engaged and the boom has something hit it with a lot of force. Think about a dozer running into the boom at speed while the machine is parked or the machine is tied onto a trailer for transport and the machine hits a bridge. The other way to abuse the swing box is running the machine with no oil in the gear box or never changing it when called for in the manufacturers recommended interval. Not enough grease in the ring gear tub causes sliding wear on the pinion more than on the ring gear and that wear can be felt as back lash between the house and carbody. I have done inspecting on many excavators that have never had the grease in the tub checked and even had sand and mud packing in them and all it did was put that sliding wear on the pinion. Your photo shows some wear on the teeth of the pinion but whether it is abnormal would depend on the total amount of hours on the component. The damage on the pinion tooth in my opinion as observed from the photo is from some foreign object being pinched between the tooth and something else. Is there matching damage to the case?
On the second set of photos I see the broken inner race on the broken bearing and all the damage to the mounting area on the pinion. I just note it because there isn't any use in speculating about what happened.
I would not have any problem with an aftermarket pinion and sourcing bearings through a bearing house. I always sourced the seals from the dealer.

Thanks …the gear head of the pinion was wedged sideways when I unbolted the swing from the machine. They were trying to swing it to get it on the lowboy and it was wedged, so that when i took one side of the bolts out the swing assembly actually popped up on that side. the damaged teeth are just on the corners and it almost looked like it happened after the initial break…..