Pump / Motor internal leakage on Hyd system
Pump / Motor internal leakage on Hyd system
(OP)
Hi
I got a Hydraulic Winch which runs out of two pumps which are paralleled, the winch is rotated by 4 A6VM motors, the whole system is a closed loop system. i got currently a problem where i am losing charge pressure from the compensation pump during winch operation, i suspect one of the motors are leaking inside and causing this issue because we had all pumps replaced not long ago on the system. My problem is that i'm unable to find any data for the flow rate on the Case Drain on these motors (A6VM), any ideas from some one who have experience with these motors on what the case drain flow should look like ?.
Thanks
Marvin
I got a Hydraulic Winch which runs out of two pumps which are paralleled, the winch is rotated by 4 A6VM motors, the whole system is a closed loop system. i got currently a problem where i am losing charge pressure from the compensation pump during winch operation, i suspect one of the motors are leaking inside and causing this issue because we had all pumps replaced not long ago on the system. My problem is that i'm unable to find any data for the flow rate on the Case Drain on these motors (A6VM), any ideas from some one who have experience with these motors on what the case drain flow should look like ?.
Thanks
Marvin
RE: Pump / Motor internal leakage on Hyd system
A.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
The motor with the coldest crankcase is the one with the most internal leakage.
If you gave more information, you would have specific answers.
Where is the exchange valve (s)?
With an infrared thermometer and by thinking a little you can make a diagnosis.
cordially
RE: Pump / Motor internal leakage on Hyd system
I have checked all the motors and the case drain on all of them looks normal.
I'm currently having a strange problem with one of the pumps (A4VG 250), where one will produce pressure and the other will not even bother moving the gauge pointer at all, i am trying to actuate it manually in both directions but it looks like the swash plate is not adjusting. The boost pressure is all fine.
RE: Pump / Motor internal leakage on Hyd system
Fortunately, you don't give any details about your system. So I can't help you.
Attached is a diagram showing the exchange valve. Often it is flanged on the A6VM. Attached is a block diagram
cordially
RE: Pump / Motor internal leakage on Hyd system
The diagram shows the full main system, the current problem is just with the winch. everything else is working OK. for any details just let me know.
RE: Pump / Motor internal leakage on Hyd system
It's really complicated your system.
Are you losing the charge pressure at the TAP60 pump?
The displacement of A6VM engines depends on the pressure at the X port. Look at the reference on the nameplate and take the instructions to know what pressure it takes at the X port to increase the displacement. Have you checked the pressure on the pilot X?
Each engine is swept through the U port, so the crankcases should not get too hot.
I can't quite understand the Liebherr scheme. How can fresh and filtered oil be injected into the closed circuit of the winches in exchange for hot and polluted oil ????
I don't think I'll be able to help you from a distance. I am not qualified enough.
RE: Pump / Motor internal leakage on Hyd system
Here's your hot oil valve (and the answer to 73lafuite's question about where the hot oil goes). A worn hot-oil relief is quite a good way of losing charge pressure.
But then I'm not 100% convinced I'm looking at the same motor as you are - the component labelling on the drawing is a bit strange.
A.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
73lafuite "How can fresh and filtered oil be injected into the closed circuit of the winches in exchange for hot and polluted oil ????"
The normal leakage will exchange the oil. I would not design it like that, I would use a flushing valve but systems without flushingvalves do exist.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
I lack detailed documentation on these pumps, all i can find online is general pump specs.
RE: Pump / Motor internal leakage on Hyd system
1) My remarks which do not help barbican: Totally agree with Jacc, the valve serves well to cancel the flow of the pump when the pressure is too high. Indeed I have already seen closed circuits without exchange valve (example lawn mower). But it is not serious. Any particles that are a little large will be laminated in the distribution glasses, the piston pads and will break up into millions of particles the size of several molecules to manage to come out with the internal leaks. And so as long as it's in the closed loop it scratches and tears off other particles. Liebherr should have put a nozzle and a normally closed 2/2 directional valve between the A of the engines and the tank. And supply the distributor when the load increases.
2) For barbican:
2a) It is normal not to detect anything with the Flir camera, because you have a sweep of cold oil which comes through the U port of each motor.
2b) Can you answer my 2 questions of June 22, 6:42 am?
2c) Does the winch operate without load? In 2 ways? Do you lose the boost pressure at the TAP60 pump when there is a large load? Or if you leave the winch brakes closed? Does the A4VG180 pump on the same shaft as the faulty pump 250 give flow? If not, then the coupling is not in place.
RE: Pump / Motor internal leakage on Hyd system
The winch will operate without load but only in one direction which is UP, the down direction will cause the pumps to lose charge pressure,
When there is a load on the winch, the problem will be apperent mostly when lowering the load, the charge pressure will drop at that time just under 10 bars. It should be sitting at 35 bars.
The coupling is fine because the A4VG 180 pump on the back of the A4VG 250 pump is operating fine. I
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
- I think I found it. It appears to control flow to shift the swash plate, so it's not charging anything.
RE: Pump / Motor internal leakage on Hyd system
Did the system ever function right after all the pumps were replaced? Perhaps moving the valve block from one hoist pump to the other would tell if there is a failure in the valve block or the pump.
RE: Pump / Motor internal leakage on Hyd system
you are correct, the brakes operates of the TAP60 pressure as well, but because of something that is dropping the pressure on the TAP60 pump, the brakes are losing pressure as well. once that happen i will stop the hoisting to prevent getting the brake packs welded.
The TAP60 pump has been replaced with a new one and has been tested.
The system was working prefect after the pump replacement. this problem happened just recently and just suddenly.
Swapping the control valves is a good idea to do a simple test, will definitely try that.
RE: Pump / Motor internal leakage on Hyd system
Also - I'm tired of looking all over the drawing - what zone are those check valves?
Found them - those provide identical pressure to both sides of each pump and don't seem to be critical to pump function as much as to bleed air from the system.
RE: Pump / Motor internal leakage on Hyd system
Are the H62 valves properly closed?
Look for particles in the filters. If it is bronze it must be from abnormal pump or motor wear. If it is black or white plastic it may come from the 1/4 turn valve seats. In this case after a complete shutdown of the whole system and zero pressure everywhere, the lever of the defective valve turns freely.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
these valves are used for emergency operation of the winch in scenarios where you need to release the brakes and lower a load. motors will start to turn due to the hanging load, the oil flow produced by the rotation of the motors will go trough these orifice's once the H62 valves are open, the orifice's are there to limit the speed of rotation of the motors during lowering.
RE: Pump / Motor internal leakage on Hyd system
One of the steering pumps is also used as a feed pump. There is proportional relief valve in that circuit, it could be something with that.
To 3DDave: You should take a look at the concept of closed loop hydraulics. Here is a good start: https://www.youtube.com/watch?v=zyzsTfADvJA
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
That steering pump you are referring to dumps its oil to the main hydraulic tank once the relief valve opens at 290 Bar, it is not connected to the feed pressure system.
I am currently in progress of replacing the pump which is unresponsive with a new one, that is because i am out of ideas. i'll let you know of the results.
PS
its so damn difficult to do a case drain test on this system, all the pumps are connected to pipes instead of hydraulic hoses, the case drain pipes are branched to all the other motors and the space between everything..... you can barley fit your arm between these pipes. a such test will require me to modify a lot of the pluming, something i don't want to even think about, due to the amount of things that have to be considered.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
It seems to me the W port goes into the feedpressure manifold. Yes, no oil unless the valve opens but it is controlled by a proportional valve so potentially it could ad to the feed circuit. If it was a normal relief I would think it would be connected to tank.
RE: Pump / Motor internal leakage on Hyd system
I have reviewed the Schematic and indeed that pump does serve as well as a feed pressure pump, but only for the Luffing cylinder and it's pump lines. it is controlled by the 4L-Y02 valve which is always closed during steering mode. I can't find any path for this circuit to get oil into the other main feed pressure circuit which is supplied by the TAP60 pump.
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
RE: Pump / Motor internal leakage on Hyd system
The hydraulic diagram of the hoist gear is perfect for selling spare parts. But not for the image of the manufacturer to whom we will blame a very low lifespan. You must absolutely add a normally closed 2/2 directional valve plus ø7mm nozzle between the B of the A6VM motors and the A7 filter. A Hydac WS10Z type dispenser without a nozzle may also be suitable. And supply the distributor coil when the pressure at A of the A6VM is greater than 50bar for more than one second. Rexroth will never make the warranty with this scheme.
After each opening of the circuit, it is advisable to clean the circuit: Bypass an A6VM motor, supply the distributor coil, tilt a pump to 25% of the maximum flow and have hot oil.
RE: Pump / Motor internal leakage on Hyd system
I would be interested to know what you have discovered to resolve your problem.
cordially
RE: Pump / Motor internal leakage on Hyd system
I will for sure let you guys know what was causing this once i disocver the cause.
RE: Pump / Motor internal leakage on Hyd system
A lot of work to intervene on such a system!
A photo of the A6VM or the Rexroth reference should show if the exchange valve is installed when it is not shown in the diagram.
If there is no exchange valve: when you cycle at low load and high speed, the temperature in the closed circuit rises too high. In this case the viscosity becomes too low and there is abnormal wear at least of the distribution plates of the pumps and motors. You should notice that the gaskets on the pump and motor flanges are burnt.
For my crop: what type of oil is used on these cranes?
Good luck
RE: Pump / Motor internal leakage on Hyd system
The A6VM's on the system does not have any exchange valves, the only exchange valve i have discovered in the system is the one mounted at the generator pump. on the diagram it is located at the lowest right and has the 503.20.01.10 as a part number. i checked that valve and it is working ok.
i have already taken apart all pumps by now for inspection and i am impressed by how clean they are considering a unit which runs for 3 to 4 days continuously every week. i'm no hydraulic design expert but what i can say is that these machines has been running on the same original hydraulic parts for over 10 years on this design. they do get hot but we never had a problem.
shell tellus 68 is the oil that is being used.
RE: Pump / Motor internal leakage on Hyd system