Ex70 excavator ram snapped

[Countrygal]

We just had our ram rebuilt last week as it broke and it snapped today while being very easy on it.
Any ideas why it may have snapped again?
Apparently this ram was rebuilt back in 2013 as well.

 

[Junkyard]

What broke? Polish rod? Barrel? Clevis? Which cylinder was it? Anything else binding up? Making contact? I've had new polish rods made that seem to be brittle. Also, the torque it takes to break the piston nut loose sometimes gets up there and can be hard on the rod. I had one take over 6,000 ft lbs. it didn't shatter on the bench but did a short time after. I always wondered if the twist I had on it was a contributing factor. Take some pics and perhaps we can help determine the cause. Could be relief valve pressure Yours isn't a large machine so I can't see that torque values on the nut could cause it. Who knows. Pics will tell us a lot.

Junkyard

 

[Countrygal]

Ram pictures



Here are two pictures.

 

[Nige]

Is it a trick of the camera in the top photo or does that rod look bent, especially close to the break..?

I see welding repairs to the end of the boom in the 2nd photo. When were they done..?

What was the "rebuild" you mention in the OP that was done to the stick cylinder..? Was the rod repaired or replaced..?

 

[Countrygal]

Farmacia bowmer

We just purchased this unit two weeks ago. We really know nothing about it other than all three rams were rebuilt in 2013.

There is a definite bend in the rod that was replaced last week.

I'm thinking the rebuild is fine and there is something much bigger going on.

 

[Nige]

The $64k question is whether the bend was there when it was installed after the most recent cylinder rebuild, or it has bent in service and that's what caused the failure.

 

[Wytruckwrench]

I would guess that the operator left the bucket down in the ground and backed up. Bends the rod then breaks it.

 

[lantraxco]

I would guess that the operator left the bucket down in the ground and backed up. Bends the rod then breaks it.

Only if the port reliefs are nonfunc.

Nige mentions the boom repairs, wondering if perhaps the stick is no longer true to the boom, putting a side stress on the rod. Doesn't take much with tight pins and an induction hardened rod.

 

[Nige]

Nige mentions the boom repairs, wondering if perhaps the stick is no longer true to the boom, putting a side stress on the rod. Doesn't take much with tight pins and an induction hardened rod.

That was kinda the way my mind was working. The issue with a lot of problems like this one is to get the full story, and when a machine has recently changed hands like this one has that makes it even more difficult. I'd bet money that something isn't straight somewhere.

 

[Wytruckwrench]

Good point, I was looking at it on my phone and didn't see the boom repair.

 

[Vetech63]

Check the top of the cylinder barrel for any scrapes or hits, check the rod too. I had a JD do this after the operator lifted the boom under a bridge and the stick cylinder barrel hit a girder. They didn't notice it until it broke later that day.

 

[Vetech63]

I just realized the op said "snapped again". I would concur with something not aligned right.

 

[Bls repair]

How much slop in the boom to dipper pin and bushings?

 

[Welder Dave]

What exactly were you doing with the machine when it broke? I see there's snow on the ground, was the ground frozen? Also banging the bucket to break lumps or penetrate hard ground can bend the stick cylinder. I ripped the top swing post mount right off my backhoe trying to dig some frozen ground.