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Thread: Volvo EC15B swinging problem by arm move down

  1. #131
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    Quote Originally Posted by v8druid View Post
    Damned if I can see how that works .... deffo not a balanced type valve as no pressure both sides

    Any numbers on the valve Wowe and who's valve block is it ?
    Wowe,

    spent some time last nite and this morning. Got enlightened. The functionality is actually straightforward. Think what happens when the spool moves from right to left. It opens way from A to T and at the same time opens way to the LS valve B-side to sense if there is too much load. Additionally, Pump connects to the B-side through the compensator. If the ram sinks, the reason for that is the main spool.

  2. #132
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    Quote Originally Posted by wowe View Post
    The block is from Rexroth. Type: SX 12 Number: 08100930



    You can immagine it. There is a pic where I hold the complete assembled valve. You can see through the holes the piston part. This part is pressed softly into the seat of the outer part (to the left at the pic). At another pic you can see the inner piston. You can push it to the left then the Piston is lifted from the seat an the fluid can flow between the front of the valve through the many holes around the outer part. If you look to the drawing of the complete hydraulic valve for the boom you can see that this is the flow from pressure-area to the tank. So I say that with tis valve the boom must sink.
    I must be more exactly:

    You can immagine it. There is a pic where I hold the complete assembled valve. You can see through the holes the piston part. This part is pressed by a weak spring softly into the seat of the outer part (to the right at the pic). At another pic you can see the inner piston. You can push it to the left then the Piston is lifted from the seat an the fluid can flow between the front of the valve through the many holes around the outer part. If you look to the drawing of the complete hydraulic valve for the boom you can see that this is the flow from pressure-area to the tank. So I say that with tis valve the boom must sink.[/QUOTE]


    I made a drawing:

    Zeichnung Anti Cav Ventil.jpg

    I made a technical study and I had some physics - but itīs hard to think that this valve is the right one. This valve must produce this sinking effect, or I am mad - may be.

  3. #133
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    Quote Originally Posted by Mattir View Post
    Wowe,

    spent some time last nite and this morning. Got enlightened. The functionality is actually straightforward. Think what happens when the spool moves from right to left. It opens way from A to T and at the same time opens way to the LS valve B-side to sense if there is too much load. Additionally, Pump connects to the B-side through the compensator. If the ram sinks, the reason for that is the main spool.
    Hello Mattir,

    what you describe is the normal function of an movement: The fluid can flow from Section "A" back to the tank and at section "B" the fluid is pressed so it can move the Piston in the RAM.

    When my boom sank, the "main spool" (this complex hydraulic steering Piston) is in the shown neutral mid-position: "A" to "T" AND "B" to "T" is closed. Of course - a wrong secondary valve can bypass the hydraulic piston and open a way from "A" to "T".

    regards wowe

  4. #134
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    Quote Originally Posted by wowe View Post
    Hello Mattir,

    what you describe is the normal function of an movement: The fluid can flow from Section "A" back to the tank and at section "B" the fluid is pressed so it can move the Piston in the RAM.

    When my boom sank, the "main spool" (this complex hydraulic steering Piston) is in the shown neutral mid-position: "A" to "T" AND "B" to "T" is closed. Of course - a wrong secondary valve can bypass the hydraulic piston and open a way from "A" to "T".

    regards wowe
    Yes, if the spool (piston) leaks from A to T in neutral position, then there is a possibility for the Ram to sink. That happens in case the ram seals are leaking as well.

    Take a look at this. It is quite enlightening. At least for a rookie like me.
    https://youtu.be/4REdJIW6-Kg

  5. #135
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    Quote Originally Posted by Mattir View Post
    Yes, if the spool (piston) leaks from A to T in neutral position, then there is a possibility for the Ram to sink. That happens in case the ram seals are leaking as well.

    Take a look at this. It is quite enlightening. At least for a rookie like me.
    https://youtu.be/4REdJIW6-Kg
    But this is not my problem. The test has shown: If I replace this "anti-cavitation-valve" by a plug which separates "A" and "T" all time, then the Arm doesnīt sink. This means, that the fluid Controlling Piston in the hydraulic valve is positioned in the neutral mid and no "A" to "T" Connection is open.

  6. #136
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    Quote Originally Posted by wowe View Post
    I must be more exactly:

    You can immagine it. There is a pic where I hold the complete assembled valve. You can see through the holes the piston part. This part is pressed by a weak spring softly into the seat of the outer part (to the right at the pic). At another pic you can see the inner piston. You can push it to the left then the Piston is lifted from the seat an the fluid can flow between the front of the valve through the many holes around the outer part. If you look to the drawing of the complete hydraulic valve for the boom you can see that this is the flow from pressure-area to the tank. So I say that with tis valve the boom must sink.

    I made a drawing:

    Zeichnung Anti Cav Ventil.jpg

    I made a technical study and I had some physics - but itīs hard to think that this valve is the right one. This valve must produce this sinking effect, or I am mad - may be.[/QUOTE]

    Wowe,

    your reasoning makes a lot of sense. The right hand side (tip) is pressurized by the ram (A) and as you describe, it lets flow through in case the tip side has greater pressure than the other side.

    if and when you have identified the anticav. valve, alias secondary valve as the quilty party, the ram sinking issue is solved. Good.

  7. #137
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    Successful finished repairing

    Hello to all,

    I can tell you, that the digger works now fine. I removed this wrong secondary valve and replaced it by the original plug. Now the boom is fix!!!!!

    Thank you very much for the support in this forum. It is the best place to get a support for a solution.


    Best regards

    WoWe

  8. #138
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    Quote Originally Posted by wowe View Post
    Hello to all,

    I can tell you, that the digger works now fine. I removed this wrong secondary valve and replaced it by the original plug. Now the boom is fix!!!!!

    Thank you very much for the support in this forum. It is the best place to get a support for a solution.


    Best regards

    WoWe
    Glad that you finally solvd the problem, thanks for the report

  9. #139
    Building Site Manager v8druid's Avatar
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    a curious fault, but glad to hear it has been solved ....... at last
    If it's got tracks, wheels, t*ts, or an engine, at some point it's gonna give you trouble!!

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