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  1. #1
    Gold Member
    Join Date
    Aug 2005
    NW Pa.
    Kubota L3400

    Default WR Long Grapple

    I have had one for several years and it is the handiest "Tool" to have. The only thing that bothers me is that some times lifting heavy large rocks, logs etc., the bucket will creep open and the load will fall out. So I keep hitting the (close) relay to keep the pressure on.

    My question? Can I put an inline check valve on the grapple cylinders.

    I have seen them in the Surplus Hydraulics catalog.

    JW 5875

  2. #2

    Default Re: WR Long Grapple

    " So I keep hitting the (close) relay to keep the pressure on."

    ok you need to be asking yourself why you loosing pressure between the valve and the cylinder, when lifting heavy loads.
    So the load still holds when you have the valve open, and keep supplying it with oil from the pump. Therefore we can say 2500 PSI holds the load ( I dont know your machine, but I will take a guess its 2500 PSI ).

    So why we loosing pressure in the line then?

    1/ Is there any external oil leaking from that circuit?
    2/ Seals are interanlly leaking in your cylinder ( most probably )
    3/ Control valve is leaking internally ( not very common, but have seen it happen )
    4/ If that Grapple circuit is fitted with secondary relief valves, then the load could be too heavy, and the pressure has reached the set pressure on the secondary relief valve and it dumping some oil back to tank.

    Or the secondary relief valve is adjusted to low or the seals are leaking internally.

    Adding a check valve will not solve the problem if you have leaking cylinder seals.
    Adding a check valve to the circuit would cut out, the secondary relief valve if you have one. The secondary relief valve is there to protect your circuit.

    If you were going to add a check valve, it would have to be a pilot operated check valve. A normal check valve would not allow return oil back to tank.
    A pilot operated check valve has pressure oil from the other side of the cylinder to open the check valve to allow return oil back to tank.


  3. #3
    Gold Member
    Join Date
    Aug 2005
    NW Pa.
    Kubota L3400

    Default Re: WR Long Grapple


    Thank You for the reply and jogging the "Grey Matter" (Brain).

    I will check the solenoid control valve for it's limits. I do not have any leaks in the lines or the cylinders. When storing the unit, I connect the hose lines together, and depending on how wide I leave the grapple open, sometimes it will bleed down. This would be that the cylinders are in "Series" and just pushing fluid back and forth? However I do suspect that when the grapple is on the tractor, my solenoid valve may be letting fluid by pass from both cylinders when under load.


  4. #4
    Advertiser kennyd's Avatar
    Join Date
    Jul 2003
    Westminster, MD
    John Deere 4110, 455

    Default Re: WR Long Grapple

    I will bet a dolar that the cylinder seals are leaking/bypasing internally. You won't see anything...but the fluid is moving from one side of the cylider to the other past the piston seals. If your grapple has two cylinders, then only one has to be leaking to get the problem you have.

    You could add a DPOCV like a lot of top link cylinder have, but like Duff wrote if the seals are leaking/bypassing internally then it won't help. Grapple cylinders are small, and live a tough life because they are always forced to the stops to clamp a load.

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  5. #5
    Bronze Member
    Join Date
    Oct 2004
    Eastern, NC

    Default Re: WR Long Grapple

    Depending on your valve kit we have a check valve designed to help with type issue. Normally it is an issue when trying to carry a heavy fairly slick load like a concrete pipe.

    I'll be happy to help you with it.

    W. R. Long Inc.

  6. #6

    Default Re: WR Long Grapple

    "depending on how wide I leave the grapple open, sometimes it will bleed down. This would be that the cylinders are in "Series" and just pushing fluid back and forth?"

    Ok this bleeding down by its own weight, even though the hoses are hooked together, tell's me your seals are not very tight in the cylinder.
    When you reseal a cylinder with new seals and the cylinder is within specification, you will struggle to pull the rod out by hand. It really takes allot of force.
    Now this is not 100% way of telling that your seals are gone in cylinder, but its a pretty good indication !!

    In the grapple its only a very small volume of oil, it only takes a small couple of drops to leak between the seals in your cylinder, and it will drop your pressure internally by quite a bit.

    I was thinking more about the pilot operated check valve today, and it would actually be a good idea to fit.
    This will not solve your problem with leaking seals in your cylinder.
    Adding the pilot operated check valve will add some safety to your grapple. The last thing you need if you blow a hose is to be dropping your load, especially if someone is near by.

    All the best

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