320BL SWING MOTOR FAILURE

[uffex]

Good day Jon
If I am understanding your thread correctly the hose marked blue had its connection position changed to the tank, that is not correct to move the hose, when the machine is running the blue hose must have a minimum of 35 p.s.i and when you swing and let go of the RCV to stop the pressure must remain positive (Not zero). I suggest you check in the parts book check where that hose should connect make it good - adapt a low pressure gauge into that line and make sure you have the correct pressure. The pressure levels I give are the norm. for swing motors as I do not have Caterpillar information privilege's there are guys on the forum that can help with the exact numbers however in that absence use what I have given you. Excessive case drain pressure will only cause seal failure and be the root cause of swing motor failure.
I hope the information helps you to get it sorted
Kind regards
Uffex

 

[Nige]

4MR-prefix is a Japanese-built machine built for the Japan-only market. A Japanese parts manual is reference XJBP7614.
The equivalent of this machine is a 5BR or 6CR-prefix. Both models were built in Japan but were for sale to the World market as opposed to the Japan-only market. Parts Manual XEBP7645.
I've attached the hydraulic schematic for that series of machines. Actually it suits all three S/N prefixes.

 

[heymccall]

Excessive case drain pressure will only cause seal failure and not be the root cause of swing motor failure.

In the case of gear motors, yes. For this piston motor, excess case drain pressure can, and does, cause slipper shoe failure. Are you gonna make me dig back to find the info that led me there?

 

[uffex]

Good day Heymccall
Thats new but we can all learn something new thats what the mind likes any idea as to the theory behind that statement ? Nige do you have a good illustration of how the replenishing line should connect ?
Kind regards
Uffex

 

[jonbates5]

The one in blue is NOT the case drain.

Case drain is 1/2" hose from swing motor to tee at swivel, then from tee at swivel to return filter.

Gauge must be tee'd in, not just blocking port.

that's where we had the gauge tee'd in, on the half inch line in my picture that a yellow line with the orange line i drew on it.

 

[heymccall]

First google hit on "Caterpillar case drain restricted". I know there is more info on case drains for piston motors out there.

https://www.hydraulicspneumatics.com/hydraulic-pumps-motors/catch-22-filtering-case-drain-lines

 

[heymccall]

 

[heymccall]

Return from swing motor goes to #5

 

[Nige]

Uffex, are these any use to you..? The probllem is that no single parts illustration shows all the hoses.

 

[heymccall]

Smaller machine, same concept.

 

[uffex]

The explaination does not make a great deal of sense to me however I except your statement and lodged it in my memory and thank you for coming back.
Kind regards
Uffex

 

[heymccall]

And to clarify why MY swing motors failed. Both saw excessive slipper shoe damage and complaint was low swing torque followed by overswing.

After replacing the original and replacing the remanufactured swing motors, it was found that the case drain filter had not been changed for over 6k hours, leading to the initial failure. And, obviously the replacement motor failure.

I can assure you that case drain filters never remain on my machines anywhere near that long anymore.

 

[uffex]

Good day Heymccall
I make one comment excessive case drain pressure comes from a damaged motor or blocked filter, the motors shaft seal cannot take excessive pressure and will blow you can see many examples of that on the forum. Providing replenishing pressure is maintained there must be little risks to the slippers only in "very exceptional circumstances" to quote the Abstract article on the web. I am sorry not convinced by either articles it would be nice to question the authors somewhat.
We all have our ideas which remain until convinced otherwise.
Kind regards
Uffex

 

[heymccall]

Not here to argue...
I only know from my experience, and from those who have helped solve the problems presented to me. The moment the failed reman swing motor hit the shop, I was told to verify case drain. They insisted that the case drain circuit was restricted. Had that machine for 17,000 more hours, and never touched the swing motor again.
In 25 years, I have only encountered one (technically, two) swing motor slipper shoe failures.
The three swing motor output seal failures that i have encountered were all worn/ hardened seals.
There is no argument that a makeup line pressure issue "can" cause slipper shoe failure. It's just that I personally have not encountered that. Perhaps someone else has more experience?


I also don't understand how bucket or dipper operation would increase case drain pressure, as the original poster has stated?

 

[DEMLONE70]

High case drain pressure from motors or swivel leads to swing motor faillure .
Its proven by Cat

 

[heymccall]

The original poster say dipper and bucket function make the case drain hit 150psi.
Could full pump pressure, when stroked on other functions, leak enough through travel spools to pressurize the swivel, and then flow from bad swivel seals to the case drain?
Could he be testing wrong?

 

[jonbates5]

The original poster say dipper and bucket function make the case drain hit 150psi.
Could full pump pressure, when stroked on other functions, leak enough through travel spools to pressurize the swivel, and then flow from bad swivel seals to the case drain?
Could he be testing wrong?

The test was performed by a Cat mechanic. $2400.00 worth of testing to be exact. I witnessed the testing and the locations he took the tests. he tested the swivel and track motors by wedging a pin in the tracks and having me attempt to move against it. the case drain stayed at the -50lbs with the gauge tee'd into the 1/2'' line on the top of the swing motor. then he decided to let me operate the machine and that's when we discovered the pressure spiking intermittently to as high as 150 but only when reaching out to get a bucket of dirt. no other time and not all the time. I don't understand the reason for moving the makeup pressure line like he did other then he said it would isolate it from the elevated case drain so it wouldn't affect it. After reading this thread I am thinking that's not the right thing to do.

 

[jonbates5]

The test was performed by a Cat mechanic. $2400.00 worth of testing to be exact. I witnessed the testing and the locations he took the tests. he tested the swivel and track motors by wedging a pin in the tracks and having me attempt to move against it. the case drain stayed at the -50lbs with the gauge tee'd into the 1/2'' line on the top of the swing motor. then he decided to let me operate the machine and that's when we discovered the pressure spiking intermittently to as high as 150 but only when reaching out to get a bucket of dirt. no other time and not all the time. I don't understand the reason for moving the makeup pressure line like he did other then he said it would isolate it from the elevated case drain so it wouldn't affect it. After reading this thread I am thinking that's not the right thing to do.

I might add this machine has 2 pumps also.

 

[jonbates5]

Good day Heymccall
I make one comment excessive case drain pressure comes from a damaged motor or blocked filter, the motors shaft seal cannot take excessive pressure and will blow you can see many examples of that on the forum. Providing replenishing pressure is maintained there must be little risks to the slippers only in "very exceptional circumstances" to quote the Abstract article on the web. I am sorry not convinced by either articles it would be nice to question the authors somewhat.
We all have our ideas which remain until convinced otherwise.
Kind regards
Uffex

I noticed the case drain filter was replaced but also all the case drain lines look to be original and so I am wondering if perhaps a collapsed or peeling hose might be the problem by restricting the flow?

 

[uffex]

Good day guys
I would like to make the point that I have worked from manufactures data and my own experience, if I come over as being confrontational may I apologise for that. I believe we can all learn from one another by understanding what has caused problems and it is to that end I contribute to the thread. A document produced by a major equipment outlet cannot be taken at face value folk can be mistaken which I include myself.
When I look at the actual motor manufacturer installation data many warnings are published towards the end of the document none of which refer to high case drain other that the specification, if the machine can generate such high case drain when using the equipment suggests to me some other issue.
So we are all coming from the same place I attach the information for your observations.
Kind regards
Uffex