Hydraulics not smooth on the H10MBE

[Paska]

Hi again.

Our H10BE works very smoothly. I just corrected the servo pressure on the H10MBE to 68 bar and the hydraulics don't feel nearly as smooth as on the H10BE. It doesn't shake but it's difficult to move it very slowly and also the engine seems to be much more easily overloaded. I would think as this is a load sensing system the pressure differential for the LS system might be set too high and the pumps are trying to push too much oil there? Maybe the previous owner tried to fix it by lowering the servo pressure. Again the swedish adjustment instructions are a bit cryptic so I don't know exactly what to adjust and where to measure the pressures

[Jac]

These are not LS, I think it is OpenCenter but the pumps are variable and have a power regulator.
If the powe regulator is adjusted too high it will bog down the engine. But BEFORE you start messing with the power regulator make sure the fuel system doesn't have clogged lines or filters.
We have seen it many times here on the forum, people think that there is something wrong with the hydraulic system because "the hydraulics kill the engine" and then it turns out that they just needed new fuel filter or there was a fuel hose with microcracks sucking air.

I don't have any ideas for why it is not smooth to operate. Maybe some extra function is stuck halway on so that the pumps always have a bit of pressure?

[Paska]

Interesting, we have a 60's O&K RH 6 that has an open center valve system with a power regulated piston pump. It behaves completely differently, there is a constant loud hissing sound whenever you move the hydraulics slowly or even at less than the current flow of the pump. These åkermans behave more like LS and I would have thought that they didn't stuck in the 60's for 30 years?

Anyway, the fuel filters are new, we had a fuel transfer pump fail on the track machine last year that caused a huge power loss but this has all the power.

[akkamaan]

I just corrected the servo pressure on the H10MBE to 68 bar and the hydraulics don't feel nearly as smooth as on the H10BE.

Is it the pilot pressure for the joysticks you refer to?
Increasing that pilot pressure will shorten the response time and make the function respond quicker. If your directional valve needs 5 bar pilot pressure from the joystick to start a motion and 15 bar for full speed there is an optimal pilot pressure that should feed the joysticks. I know one pilot valve manufacturer recommends a main pilot pressure 10 bar over max used pressure. In my example that would be 15+10=25 bar. According to reliable manufacturer sources a too low feeding pressure will make the function's response slower. And accordingly, the function will overreact when feeding pressure is too high. Obviously that's what happened with you system, hard to operate in slow motions

[Paska]

I don't know if what they refer to as the servo pressure is what actually adjusts the pump flow rates or uses the hydraulically controlled valves and joysticks or both? Anyway, I adjusted it with a new gauge to the book value upper tolerance limit. A few bar difference down doesn't make a difference in how it feels like. So the actual misadjustment or fail must be somewhere else.

[akkamaan]

I don't know if what they refer to as the servo pressure is what actually adjusts the pump flow rates or uses the hydraulically controlled valves and joysticks or both?

Pilot pressure for pump flow is usually not used since the pumps adjust that internally with the actual pump pressure. But a hydrostatic drive pump can be of the type that uses pilot pressure for flow regulation

Anyway, I adjusted it with a new gauge to the book value upper tolerance limit. A few bar difference down doesn't make a difference in how it feels like. So the actual misadjustment or failure must be somewhere else.

What was the tolerable range of pressure advised by the book? Of course, a few bars change from "65" to 68 bar will certainly not have a noticeable effect. Ackording to the book PS (Pilot Servo) pressure should be set at 6.5 MPa or 65 bar, and this pressure is used for the joysticks

Our H10BE works very smoothly. I just corrected the servo pressure on the H10MBE to 68 bar and the hydraulics don't feel nearly as smooth as on the H10BE

What was the reason for raising the PS pressure?
Did this symptom occur AFTER you adjusted to 68 bar?

[Paska]

I don't know if what they refer to as the servo pressure is what actually adjusts the pump flow rates or uses the hydraulically controlled valves and joysticks or both?

Pilot pressure for pump flow is usually not used since the pumps adjust that internally with the actual pump pressure. But a hydrostatic drive pump can be of the type that uses pilot pressure for flow regulation

Anyway, I adjusted it with a new gauge to the book value upper tolerance limit. A few bar difference down doesn't make a difference in how it feels like. So the actual misadjustment or failure must be somewhere else.

What was the tolerable range of pressure advised by the book? Of course, a few bars change from "65" to 68 bar will certainly not have a noticeable effect. Ackording to the book PS (Pilot Servo) pressure should be set at 6.5 MPa or 65 bar, and this pressure is used for the joysticks

Our H10BE works very smoothly. I just corrected the servo pressure on the H10MBE to 68 bar and the hydraulics don't feel nearly as smooth as on the H10BE

What was the reason for raising the PS pressure?
Did this symptom occur AFTER you adjusted to 68 bar?

The reason I adjusted it was because the hydraulics were slower and weaker than on the track machine and the Ps warning light was blinking sometimes. The issue was completely solved. I don't know what the pressure originally was because I measured at the wrong point at first but I can tell it was much too low.The tolerance was 65 +- 3bar but some people here have used 75 bar without issues from what I read. It acts just the same at 62 bar.

I think now that I used it more that most of the issue happens when the boom float option is on. The other moves are smoother. So the main issue is on the main boom down movement, when using it in single acting mode. It doesn't want to start moving very slowly and then suddenly goes. It's a bummer since it's mostly used in single acting mode.

IDK if the hose rupture valve could do this somehow? Anyway, it would be nice if someone who had a similar issue could point out what the problem was, to avoid beating around the bush.

[Paska]

Here is a video if it, it's not impossible to use somewhat smoothly but the sudden movement causes the machine to rock on the wheels sometimes. You can also hear there is hissing sounds on other moves too, on the track machine only the main boom down movement makes a sound, as I think it's supposed to work.

[Paska]

Update, it works smoothly if the handbrake is on for some reason. Some guru might know why, is the pump arrangement connected differently when the drive hydraulics are on? I haven't used the handbrake just because the brakes don't work. I will repair them next summer if I can. But I think now it works about as good as the track machine.

[Anton]

When the handbrake is open, there is servo pressure on the brake. When the brake is on, the servo pressure is trained and the brake is depressurized. (Negative brake)

[akkamaan]

Update, it works smoothly if the handbrake is on for some reason. Some guru might know why, is the pump arrangement connected differently when the drive hydraulics are on? I haven't used the handbrake just because the brakes don't work. I will repair them next summer if I can. But I think now it works about as good as the track machine.

If it takes servo pressure to release the handbrake (negative brakes as Anton says) there might be a leak (internal or external leak) on the parking-brake release circuit which causes a pressure drop on the servo circuit for the joysticks and causes them not to work properly