Problems with PM trailer hydraulic crane

[Pixel123]

Hi! This is my first post, so please bare with me.

We have a pretty old PM hydraulic trailer crane which powers a hydraulic pump from a 4 cylinder Deutz engine which can lift approx 1.5 ton.
The crane has load/hose break protection on every cylinder. There is 1 piloting line which is connected to these different valves on the cylinder.

On a sunny day when I was sitting in the seat next to the main boom suddenly I got a non-mineral oil washing . One of 2 controlling valves of this piloting line cracked, opening the way for the oil.
These 2 controlling valves are in series. I took the broken valve to a local hydraulics center. However, there was no type number or anything on it, so it couldn't be identified.

They told me that usually the only thing these protection valves on the cyclinders need is a pressure reducing valve, so they "gave" one, a Walvoil VRPRL38 (100-200 bar range) it is the one below:



You can also find it on this link, page 11.

I mounted this valve between pump and tank, and the regulated pressure is connected to the piloting line.

- I can control the main boom but the motion is slightly unstable (when going up, it is not a smooth motion, but shaky)
- When I let go of the control lever, the main boom cylinder slowly retracts, which was not the case before, it was completely still. So it is definately not the cylinder leaking in itself.
- Whatever I put for the control pressure, it keeps showing above behaviour

In my hope of debugging this I rubbed the protection valve clean on the main boom and found following type:



With a quick search I ended up with: "1E45P4W35S11 overcenter valve 70 - 350 bar"
However I cannot find additional data on this. If you have additional data on this, this would be grately appreciated.
I then started looking into these overcenter valves. But I always see diagrams of double acting cylinders. I only found 1 metal line going to the cylinder, so I think this is just a single acting cylinder.
I don't see how this is connected or what I am doing wrong. Any ideas?

Thanks in advance!

 

[oldnslo]

Pixel,
Eaton purchased Integrated hydraulics several years ago so finding information has proven more challenging. My guess is that the Integrated valve is a counter balance or "over center" valve but I cannot find a single document to prove this. A pressure reducing valve would NOT perform the same function.

 

[Pixel123]

Hi oldnslo,

I am certain that the valve on the cylinder is a 1E45P4W35S11 overcenter valve 70 - 350 bar which is shown in the second picture. However there is a pilot line going to this valve. And this pilot line was originally controlled by 2 valve blocks in series from which 1 cracked and could not be identified. These 2 "controlling" blocks I have replaced now by the pressure reducing valve shown in the first picture.

 

[oldnslo]

Pixel,
How or to what were the valves in series connected to? One end was connected to the pilot lines of the 1E45** valves. What were the other ports connected to?

 

[Pixel123]

In the picture in attachment I've drawn how it was previously connected. But I have no clue what these 2 blocks do. the T-section is just to connect it.
If i'm correct, the pilot pressure for an overcenter valve is generated by the cylinder/load itself. So why do I need a seperate tunable pressure?

I've did some research on the overcenter valves. Apperantely there are also overcenter valves with a pilot dump. I might be looking at it the wrong way. I also see only 1 connection to the cylinder, so I think it must be single acting. But it than baffles me that there are 5 connections to the 1E45... overcenter valve .

Tomorrow I will take a fresh look at the cylinder and hoses to figure this out.

 

[oldnslo]

Best guess on the five connections to the 1E45 valve block.

V1 & V2: This would connect to the directional valve controlling this function.
C1 & C2: These would connect to the cylinder.
5th port could be either external pilot or external drain line.

Since this is a crane I would be very careful in making any changes without knowing exactly what the valve is that you are replacing. Dropping the load on someone would not be good.

 

[Pixel123]

Hello oldnslo,

I debugged the problem using a pressure gauge. From 50 bar onwards on the pilot line, the cilinders do not retract anymore. It seems that the valves fixed on the pistons are piloted over-center valves and they need the pilot pressure to fully close/operate safely. If I shut down the engine (and thus the pump) I am unable to lower the load using the crane which is exactly how the safety should work. I left the crane up for a night, and it was in the exact position where I left it. I tested this with closing a manual ball valve when there was > 50 bar pressure on this line. I've now ordered a check valve with high pressure opening of 10 bar (so it also closes also very well) and I will put this on the pilot line after the pressure reducing valve and then it is fixed! Thank you for helping me crack this one!

 

[oldnslo]

Pixel,
Glad you solved your problem and have your crane back in service.