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Thread: Hydraulic Relief valve question?

  1. #1
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    Hydraulic Relief valve question?

    I have one of the top two two relief valves pictured in the link below. Forgot if it is one or two seperate valves. It is on a mortar mixer ( Grout Hog). The machine stop mixing from a mix that was to dry. Usually you can revese the direction of the paddles and it breaks free. This time the paddles turn but instead of mixing 3 bags of mortar it now only mixes 1/2 before hydraulics don't have enough power to turn.


    When the hydraulics used to stop from overload there would be a screeching sound now it does not make that noise when it stops. Would that indicate the relief valve is not working?


    Dealer was telling me it was the shear pin really (key on the shaft) from the blade shaft in the mixer that connect to the hydraulic drive motor. I doubt it would turn at all if that was the case.

    It said to turm relief valve adjustment if you have the problem I have. Can the relief valve brake? I know everything breaks but why would it need an adjustment? Does it reset itself if turned in?

    Hope a tad of this makes sense. Thanks!



    Link to valve picture below


    http://www.ezgrout.com/Manuals/Troub...0TSG/Valve.jpg


    Link to troubleshooting


    http://www.ezgrout.com/Manuals/Troub...MH-TSG-002.htm


    Was intersted in this part


    Adjust single relief on (1) 2-Spool Monoblock, Paddle relief on (2) 1-Spool Monoblock, or Main relief on 2-Spool Stack Valve by turning in clockwise all the way in.
    Last edited by Speedpup; 05-26-2009 at 09:21 PM.

  2. #2
    Super Moderator willie59's Avatar
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    Hmmm, good one. I believe I'd pull the motor, if for nothing else, to check the condition of the shaft key. If there's a problem with the shaft key, I'd like to know about before it gets worse. As for the relief changing, I suppose it's possible. Everytime the paddles hang, for whatever reason, you'll be cramming oil over the relief. Done enough times, I suppose it's possible the relief spring begins to loose some strength, making the pressure to open it go down. You could try adjusting it a little, but it's hard to know where your at without a pressure gauge connected to the circuit so you can set it to the recommended pressure. Adjusting the relief all the way in prevents the poppet from lifting off the seat. I think they are recommending this if the paddles won't turn at all. I'm not sure it applies to weak power with material in bucket. You could adjust it in until it bottoms out, then back it out maybe a half a turn, this should give you some relief under load.
    Last edited by willie59; 05-26-2009 at 09:30 PM. Reason: Added text
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  3. #3
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    The first thing I'd do is pull the relief valve out of the valve and look at it. From the picture, it looks like a standard cartridge type valve. The most common type of failure is at the o-ring and plastic backing ring at the bottom of the valve where it seats in the valve block. If this o-ring blows out, the maximum system you can generate is whatever resistance is left as the oil bypasses through the blown o-ring. This pressure would be quite low, therefore = no motor torque and no power to turn the mortar. I see that the valve is a Sauer Danfoss. If you can pull the model code and serial number off. The Danfoss website is pretty good. Around here (and in the US I believe) Berendsen Fluid Power sells Sauer Danfoss. They could likely get you a new seal kit for the relief. They are pretty cheap and dead easy to install. I would highly recommend investing in a pressure gauge so you can properly set the relief pressure after re-sealing the relief.

  4. #4
    Super Moderator willie59's Avatar
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    Quote Originally Posted by T_Gunn View Post
    The first thing I'd do is pull the relief valve out of the valve and look at it. From the picture, it looks like a standard cartridge type valve. The most common type of failure is at the o-ring and plastic backing ring at the bottom of the valve where it seats in the valve block. If this o-ring blows out, the maximum system you can generate is whatever resistance is left as the oil bypasses through the blown o-ring. This pressure would be quite low, therefore = no motor torque and no power to turn the mortar. I see that the valve is a Sauer Danfoss. If you can pull the model code and serial number off. The Danfoss website is pretty good. Around here (and in the US I believe) Berendsen Fluid Power sells Sauer Danfoss. They could likely get you a new seal kit for the relief. They are pretty cheap and dead easy to install. I would highly recommend investing in a pressure gauge so you can properly set the relief pressure after re-sealing the relief.
    I thought about that T_Gunn, but he said he had one of the top two valves on his machine, and it's hard to tell in the pics, but those two valves don't look like catridge reliefs, can't say for sure. The valve in the bottom pic is for sure cartridge relief valves. I'm thinking the top two pics are poppet type relief valves that have a poppet spool go against a seat inside the valve body and has a spring to keep poppet on seat, adjusting screw adjusts spring tension. That's the best I can see them. I have seen erosion of the seat from continued lifting of the relief, but usually on cheap valves, not Sauer Danfoss. Heck, anythings possible.
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  5. #5
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    Thanks Guys for the info. I am leaning towards the o-ring theory in the relief valve. I'll try turning it down and then pop it off to take a peek, I don't care if I get a new valve for a spare. This did happen quite abrupt so I think it may be relief valve failure from to many overloads the past two years. I was thinking it didn't have the snap it once had recently, but thought it was my imagination

    I'll mark it and count the turns where it was set.

    Now I suspect it was on it's way out. Thanks a million, now I got something to shoot at. Too bad it has been a real shooting gallery for me lately, as ATCO knows. I have been keeping him real busy as he very kindly feeds me info, solves problems and saves me money.

    Thank you both for helping keep me sane, if it's not to late!
    Last edited by Speedpup; 05-26-2009 at 10:27 PM.

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    Super Moderator willie59's Avatar
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    Heck yeah, go for it! If you take the relief apart, you could find a bad o-ring, broken spring, any number of things. Be sure and send us some pics of the goodies when your taking them apart so we'll have a better idea of what we're working on. And you might still want to check that shaft key, even if it's getting just a little worn, you can replace it now before it gets ugly.
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    If they are the same I may switch them to see if the problem goes from the one that dumps to the one that turns the paddles,


    video of the machine http://ezgrout.com/pages_products/mi...ducts_mh12.php
    Last edited by Speedpup; 05-27-2009 at 01:15 AM.

  8. #8
    Senior Member stock's Avatar
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    One has to walk before you can run, so go and buy a pressure gauge and see if it is a valve issue,from my experience I would be looking closer at the motor,is the pump and motor getting hot after a reasonably short time,if so it usually a sign of a dud unit .
    The equipment in the picture has a close interaction with personnel so fiddling with the prv's with out a gauge is a recipe for disaster.My years show that a prv deteriorates over time as do most hyd components but the motor is usual first to fail .
    Stock

    Common sense is not common practice

  9. #9
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    I'm with stock relief valves seldem go bad ,,they can back off some one can tinker thinking their makeing it better by fiddling with it but without a pressure gauge of at least 2500 lb before relif valve what the vendor said may be true broken sherre pin may hold till warms up and then slips so check preasure first

  10. #10
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    Those are cartridge style relief valves and they are set higher than the main relief. They are there in case something overpowers the motor while the spool is closed. The main relief would be the one to give you problems because as you said the auger stops turning meaning the pump isn't pushing it.

    I'm leaning towards a shear pin or key way on the connection between the motor and auger. I've seen keys sliced off clean with the shaft and then balled up into the mating bore. It will still turn some but the motor will have enough power to keep griding it up. You could be losing the coupler, the motor shaft or both by continuing to run the machine. Pull the motor and check it out before you get into the hydraulic system.

    Good Luck!

  11. #11
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    Being a one man band stinks. I gambled and ordered a valve today for 361+tax+shipping. I have no time to get a pressure gauge or even play with it much or disassemble or swap hoses. Need the machine to keep going so I ran before walking. If I call for dealer to pick up and then rent one will be hundreds in real short order. I used it today mixing 1 bag at a time. Hydraulic motor and pump never got hot.

    Was going to buy another one but it's 7+ grand slightly bigger. I was going to buy a smaller different type but it was 3600 and I could not get either for 4-5 days in any case Long Island and City of NY and nobody is stocking anything Nothing I wanted. I was looking for a poly drum mixer if I bought smaller 3000-3600 range and none to be had. 90-100 per day to rent + tax. I hate renting.

    Hate buying large stuff I can't see. The other 4 Muller mixers in my yard are old and dead after 23-25 years I had them. Original engines are still good, trannies and clutches are gone. Frames are rusted / rotted after all these years.

    probably be back tomorrow crying if it doesn't work. Anyway thanks for the tips.

    I need to buy about $8000-10,000 in scaffold plank real soon so I am trying to save on big purchases until I hook another job which may be hard. Then I have to spend the rest of the summer weekends on fixing my Lulls and painting about 800+ scaffold frames and all the accessories. That is a whole other story for me to post soon. Came home napped and now back to bed and up at 4 am to do change order proposals for the job which are growing in leaps and bounds. So many I could bury the price of a mixer in there. Crazy job.
    Last edited by Speedpup; 05-27-2009 at 09:10 PM.

  12. #12
    Super Moderator willie59's Avatar
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    Hope it works for ya, keep us posted.
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  13. #13
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    No time today so it will have to limp along another day. Then Saturday I will not be working in panic.

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    Victory was mine! Well after about 400 bucks!

    Well thanks for all the help I swapped the valve and the mixer is running great again. I dumped a bunch of dry sand in there and it didn't stop. Valve is back to screeching again when it gets over loaded. Now I can take the other on apart and see what went bad and have a spare in the truck.. So this thread or another one will pop up when I get a chance to survey the inards!


  15. #15
    Super Moderator willie59's Avatar
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    Quote Originally Posted by Speedpup View Post
    Well thanks for all the help I swapped the valve and the mixer is running great again. I dumped a bunch of dry sand in there and it didn't stop. Valve is back to screeching again when it gets over loaded. Now I can take the other on apart and see what went bad and have a spare in the truck.. So this thread or another one will pop up when I get a chance to survey the inards!


    Excellent!
    Sounds like the relief is doing its thing now. Glad you got her going.
    Ideally, though, you want to operate the mixer in such a way as to not pop open the relief as much as possible. The relief is there to keep things from breaking if the paddles get hung on something, but everything is under a good deal of stress at that point, and it will heat up your hyd oil in a hurry. .
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