TB 1140 Slew Problems

[Taat]

Hello masters!
I bought an used TB 1140 excavator and it has a slew brake problem. Sometimes the machine stops slewing after releasing the joystick command and sometimes doesn’t.

Up to now I have checked the pressure for left and right slewing at the marked ports and they both come up to spec too good 30MPa and when the machine does stop slewing the pressure immediately drops to zero. And when the machine doesn’t stop slewing the pressure stays at 20MPa, at this point you can go out of the machine and just push the whole upper structure around by hand. The slewing park brake also never applies.
I have also checked the poppets (marked 13 in the picture) and they seem to be good as well as the seats and the springs.
My next thought was that the fine swing section of the brake valve was messing with the system so I disconnected the connector as marked but it still the same (sometimes stops slewing and sometimes doesn’t).

What would be the next step to narrow down this problem?

One more note. When the slewing does stop and the upper structure holds its position and leave it like that, after some minutes it will eventually release and start to fall under its own weight if not on flat ground. So looks like there is oil coming to the brake valve even after the pressure drops to zero?

 

[V8Druid]

Hello masters!
I bought an used TB 1140 excavator and it has a slew brake problem. Sometimes the machine stops slewing after releasing the joystick command and sometimes doesn’t.

Up to now I have checked the pressure for left and right slewing at the marked ports and they both come up to spec too good 30MPa and when the machine does stop slewing the pressure immediately drops to zero. And when the machine doesn’t stop slewing the pressure stays at 20MPa, at this point you can go out of the machine and just push the whole upper structure around by hand. The slewing park brake also never applies.
I have also checked the poppets (marked 13 in the picture) and they seem to be good as well as the seats and the springs.
My next thought was that the fine swing section of the brake valve was messing with the system so I disconnected the connector as marked but it still the same (sometimes stops slewing and sometimes doesn’t).

What would be the next step to narrow down this problem?

One more note. When the slewing does stop and the upper structure holds its position and leave it like that, after some minutes it will eventually release and start to fall under its own weight if not on flat ground. So looks like there is oil coming to the brake valve even after the pressure drops to zero?

shuttles in the main slice? broken spring? does it do it in both directions??

 

[Taat]

shuttles in the main slice? broken spring? does it do it in both directions??

What do you mean by shuttles in main slice? Sorry english is not my first language. And by springs you mean the ones in the relief valves?
Yes it happens in both direction…

 

[V8Druid]

What do you mean by shuttles in main slice? Sorry english is not my first language. And by springs you mean the ones in the relief valves?
Yes it happens in both direction…

the section of the main valve block controlling the slew, actuated by the servo circuits

the springs in those

if it's both directions I can't really see it being the main valve, unless the shuttle has broken or it's seals have broken/split allowing pressure to bypass them

 

[Taat]

the section of the main valve block controlling the slew, actuated by the servo circuits

the springs in those

if it's both directions I can't really see it being the main valve, unless the shuttle has broken or it's seals have broken/split allowing pressure to bypass them

I tore down the slew hydromotor. The valve plate under the brake valve was worn out, everything seemed to be okay. After putting it back together the brakes stops slewing normally now and holds position.
What worries me still a bit is if I fully extend the boom and arm on a slope the upper structure will start to drift slowly. And if I take off the case drain there is about 1 liter of oil coming through every 10 seconds when I run the slew command.

 

[Left hooker]

Cheapest to check would be the servo controls for slew in the cab is one sticking

 

[Taat]

Cheapest to check would be the servo controls for slew in the cab is one sticking

Hello, are you talking about the 10 and 11?

 

[Left hooker]

Hello, are you talking about the 10 and 11?
View attachment 58233

Yes

 

[Mick-the-fitter]

Hang on, I would start at the brake valves on the slew motor it’s self, only needs a bit of rubber jamming it open.

 

[Mick-the-fitter]

Try SR1 and SR2, strip and clean, but also make sure nothing is stuck in the motor ports.

 

[Taat]

Try SR1 and SR2, strip and clean, but also make sure nothing is stuck in the motor ports.

I have taken a look at the whole brake valve. I cleaned and inspected all the seats and spools. I have taken out the relief valves and changed the O rings and backup rings on them, because the backup rings looked damaged. Do you mean that I should take apart the relief valves and clean them?

 

[Mick-the-fitter]

Yes strip and clean them

 

[Taat]

Just to update this thread. I fixed the problem. To do so I changed cylinder block, pistons and valve plate (also changed the bearings, main seal to the reduction unit and O-rings). After measuring the new parts I found out that the cylinder block had already been ground down -1mm according to the new one. Possibly causing some extreme internal leakage, thats probably why just changing the valve plate didn’t work even though the old cylinder block didn’t seem to have too deep scratch marks.

Anyways the slew works fine now. Feels stronger than ever. And there is no drift on an incline. There is still a lot of case drain according to my manual specifications, but for now I am gonna leave it as it is. Maybe I should’ve also replace the swash plate and piston retainer? Or maybe the oil could escape if the housing of the motor would be worn? The machine does have over 12,000 hours on it…

For anyone with similar problems, the simplest test you can do is test the case drain leakage. And if leakage is high, your slewing device probably need a new rotary group.

Sorry for the late update, I also have a weak right track that I am trying to resolve. Thanks for all the advices I got on this problem. I really appreciate it.

 

[Taat]

Hello!
So after about 100 hours the slew/swing hydraulic motor is starting to drift again.
Also much lower power. When checking the leakage to the right is gushing out with oil, when checking left the leakage is smaller but still not up to spec.
I don’t have the motor apart yet, but my assumption is that the valve/port plate will have this one sided wear pattern on it as always up to now (this will be the third time I will have it apart now). Other components will probably be fine.
Does anybody know what is going on with my hydraulic motor? I am pretty sure that I always assemble it back correctly but you never know.
I am comparing my problem with this article: https://www.hydraulicsupermarket.com/hydraulic-pump-failure.html
According to it this wear pattern indicates improper assembly, focusing on the valve plate. Except in this article the one sided wear is more noticeable on the cylinder block/rotor. I also don’t think my oil is contaminated as there would probably be different more evenly distributed wear on the components.

This is how the valve plates look like every time I disassemble the motor:

 

[doobin]

I can't help you, but I'm sure you'll get to the bottom of it and I look forward to learning how. Always nice when people post updates to problems/help they've received, both good and bad.

 

[Taat]

I can't help you, but I'm sure you'll get to the bottom of it and I look forward to learning how. Always nice when people post updates to problems/help they've received, both good and bad.

Thanks for the reply. Would you maybe know if other types of swing motors have centering holes and pins on the brake valve and the housing of the hydraulic motor?
My motor doesn’t and maybe should, since pumps do have them and it is a similar assembly.

 

[doobin]

Thanks for the reply. Would you maybe know if other types of swing motors have centering holes and pins on the brake valve and the housing of the hydraulic motor?
My motor doesn’t and maybe should, since pumps do have them and it is a similar assembly.

@Mick-the-fitter !

 

[Mick-the-fitter]

Have you tried changing the brake valve to the opposite sides?

 

[Taat]

Have you tried changing the brake valve to the opposite sides?

No, by the shape of the housing this is the correct orientation. Also none of the hoses would reach if I flipped it.

 

[Taat]

I also checked the relief valves. They are set correctly. A little short of 330bar which would be correct setting. So by that I can assume there isn’t over pressurization in the hydraulic motor to create the valve plate separation from the rotor.