Volvo EC15B the whole digger is swinging at arm move down

[wowe]

Hello,

if the Arm is moving down slow or with medium Speed, the whole digger Begins to swing. This is only at the arm moving down, not at moving up. I checked, if the mechanical play is somewhere too much - but I found nothing. So what do you Thing about the reason for this behaviour?

Regards wowe

 

[melli]

The arm control is on right joystick? The swing control is on left joystick?
That is odd.
I could see if boom and swing went at same time...would suspect an issue with pilot controls, specifically, the left joystick.
Is Arm and Swing control valves beside each other?

 

[wowe]

I only move the right stick softly forward, so that the digger-arm moves slowly down. And then the whole digger Begins to swing forward and back with the frequency of 1-2Hz.

wowe

 

[wowe]

I made a Video

https://youtu.be/jp90Fw3LUO0

 

[melli]

Oh! That isn't swing activating.

Someone will chime as to what exactly causes that...it is a valve getting stuck, then released that causes the jerkiness.
Or a solenoid....I'd look in manual, find out where the pilot line goes to valve block and check out that section.

 

[wowe]

I took a look at the hydraulic level. At the hydraulic tank there is a plastic cap, where the oil level should be. But there is no oil visible. I took a meter and did a measurement. The oil-Level is 13cm (about 5 Inch) below the should stand. I think this is a lot. I will refill the oil and then we will see. By the way: The reason, because I checked the Level not yet, was, that the seller said, the digger got a new service...

regards wowe

 

[hosspuller]

Wowe... Before you add oil, check where the boom/stick position should be to measure oil levels. The owners manual should show the proper position. The cylinders take a significant oil volume depending on position.

Also, try moving the down control more. The weight of the boom is overrunning the cylinders and pin tolerances. You're hitting the critical point of the system.

 

[wowe]

Before you add oil, check where the boom/stick position should be to measure oil levels. The owners manual should show the proper position.

thank you for the advice - I did it.

Also, try moving the down control more. The weight of the boom is overrunning the cylinders and pin tolerances. You're hitting the critical point of the system.

Maybe - but at YouTube you can see many of EC15´s at moving down the boom softly.

 

[wowe]

Only for testing I bought a 15W40 motoroil and filled the hydraulic up with 6 Litres. The whole hydraulic oil contains 33 litres. I strartet the engine and it seems as it would be much better - maybe ok. Then I greased the complete arm. But after greasing the jerky effect was back again. Surely the greasing was not the reason for the returned jerking. And the hydraulic oil didn´t foam up. So - now the easy things are done and the state is unchanged.

How will we continue the procedure? As an inexperienced digger mechanic - but I had become a car mechanic many years ago - sugggested 2 things:

1. I will remove all filters and meshes in the hydraulic circle and clean those which are cleanable.


2. I will change the hydraulic hose at the Joystick so up and down is changed. So I can see, if the behaviour has also changed and the jerking is at up.

3. Maybe I will try to reverse the buying. But the digger seem really in a good condition - except the jerky boom down movement.

Thanks for reply.

 

[melli]

Many machines have a lever to change between two types of operation (ISO/STD)...this changes the pilots ports for joystick.
You're in Germany, so I am not sure you have feature. If you did, it would change function of joysticks, and you could ascertain whether pilot pressure (joystick circuit) was to blame. My joysticks are control valves with spring return to neutral...I think.

Occasionally, I get a similar jerkiness when lifting heavy objects...I just stop and slow down, and it goes away.
Your getting it without any weight per se.

Really would be handy to do a hydraulic diagnostic...checking build up valve, pilot, relief and crossport pressures. Knowing those would narrow down the problem.

 

[wowe]

Okay - the reason for the jerky behaviour is found: It was a boom drop valve. I removed it and the arm is moving down without jerking. But: Now I have the problem, that the arm is lowering with about 1cm/s although the joystick is in neutral position. As the boom has no sinkink Problem with the boom drop valve the RAM is ok. the problem must be located before the RAM. What must I do to find the problem?

Regards wowe

 

[kthompson]

Many machines have a lever to change between two types of operation (ISO/STD)...this changes the pilots ports for joystick.
You're in Germany, so I am not sure you have feature.


The control on my Volvo ec 45 to change the operation is in the tool box on the right front side of the machine, just in front of the hyd tank. Also mine has a sight gauge for the hyd oil level on the front of the tank visible without taking the cover off. Of course they could be different on your machine.

 

[melli]

Yeah, I was thinking he could change from STD to ISO to see if the problem was related to pilot system. He appears to have found the problem.

Wowe - what is this Boom drop valve you talk about? Never heard of it. Can you post a pic of what you removed? Maybe it is the problem and needs replacing....

 

[wowe]

Here is a pic:




The "boom drop valve" supresses a sinking boom, if the hose or steering get a leak. Maybe you name it in another way.

This jerking Problem has gone - but the sinking boom is the new Problem. Any idea to locate it?

 

[melli]

I think we call that the (cross?) port relief valve. Or it could be a load check valve...I don't have that on my boom, just my boom swing.
Could be that or the seals in boom ram need replacing. On mine, the port relief valves are on the valve block in hydraulic compartment (maybe you have something extra).
The boom rod relief valve is set to a higher pressure than the boom base relief valve to account for the area differences.
I recall one can check to see if the ram seals need replacing by swapping hoses, but I am not sure...could be dangerous as there is a reason the rod and base valves are set to different pressures. Hopefully, someone in the know will chime in and help you. Best.
The relief valves are there to ensure one doesn't blow up the ram or seals in ram. With joysticks in neutral position, the boom should hold position, as the control valve has those lines in the closed position. The only way for oil to leak is through one of the port valves, ram seals or the control valve. Figuring out which one is beyond me...although, I do have a pressure diagnostic gauge, and I would check the boom pressures to ensure all is well there (I can adjust the relief pressures).

 

[wowe]

I think we call that the (cross?) port relief valve.

At Volvo it´s called "Hose rupture valve". It´s no relief valve.

I made some Trials:

1. I moved the boom up and down. What I have noticed:
If I move the arm slow down and go then back to neutral, then the sinking rate is small and about 1cm/5s.

2. If I moved the boom fast (if the Joystick is moved more to front there is a stronger movement after passing a Special Position) ang go then back to neutral, then the sinking rate is higher and about 1cm/s.


3. I supported the boom in high Position. Then I removed the lower hose and closed the lower port of the RAM (the port of the RAM which the oil is pushed in for Lifting up) by a blind plug. Then I removed the Support of the boom. The boom was absolutely fix. I waited 15 minutes and the boom was in the absolutely same Position. That means that the internal RAM seals are absolutely ok.


4. I removed also the second hose of the RAM, so that both boom-hoses ended in the air. Then I started the engine. The Joystick was in neutral Position, but on the hose which is fixed to the "down side" of the RAM, there was a massive flowing out of oil. I dont know, if this is normal.

 

[kthompson]

30 plus years ago I worked for a hyd crane company and we called those holding valves as they prevent the cyl retracting if pressure was lost for any reason well other than cyl failure. But we did have them to fail to hold along and along and we just replaced the valve (simpler setup as those were screwed into the fitting body) but I felt most of those were due to some piece of trash holding the valve from fully closing. My guess if your valve is maybe stuck to some degree and not fully opening so lowering it jerks and then if lets the load slowly lower. But maybe read it wrong maybe the valve is holding the load but still failing to fully open when load is lowering. Either way if you can not repair that valve really suggest you replace it. You need to be able to depend on the boom staying up when you cut the machine off. Sooner or later you will find something under the boom you did not want it to lead down on. It could be YOU.