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Hot weather- can't couple wetlines

Discussion in 'Trailers' started by RobVG, Sep 23, 2009.

  1. RobVG

    RobVG Senior Member

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    We have 3 newer dumptrucks with 3 pup (pony) trailers. When the drivers un-hook and leave their trailers for the day, the wet lines get hot and the pressures go up enough to make it impossible to couple the disconnects.

    You have to release the pressure by pushing in the nipple on the female coupler. This results in a small puddle of hydraulic on a city street.

    I was just wondering if anyone else had this problem and what they did about it?
     
  2. willie59

    willie59 Super Moderator

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    What type of couplers are you using? I looked at the Stucchi webstie and it said that standard wing type wet line couplers could be made up under pressure.
     
  3. RobVG

    RobVG Senior Member

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    Been using Parker 60 series

    The line for the hoist is 1" and the high lift gate line is 1/2". I helped the driver pop the pressure on the lift gate and could hear the gate drop a bit when I did it. Haven't had the problem before the new trailers arived last year.
     
  4. willie59

    willie59 Super Moderator

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    It sounds like you have a problem with the control valve that works your lift gate has excessive internal leakage causing the lines to become pressurized. I think you have a problem with the new trailers. Holding valves on the lift gate cylinders would fix this problem. But, I'm sure you don't want to have to deal with changing the component design of your new trailers, then again, you may want to call up the trailer builder and give him an earfull. If your content in being able to "hook up" with a bit of lift gate drop, the Parker 60 series coupler is your problem. It's a general purpose coupler. I doesn't compensate for pressure on the lines. You might want to consider changing to a "connect under pressure" quick couple. I don't know what the Parker coupler would be, but here's a link for the Stucchi coupler.

    http://www.stucchiusa.com/PRODUCT SERIES/APM.html
     
  5. OCR

    OCR Senior Member

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    Hot weather- can't couple wetlines:

    Now, that's a link I can connect to... lol

    Good find, ATCO... :thumbsup


    OCR
     
  6. Steve Frazier

    Steve Frazier Founder

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    I have the same problem with my 4 way bucket and grappler on my skid steer. I've tried the coupling that ATCO suggests with some success, but it has its limitations. My solution has been to cycle the attachment a few times just prior to disconnecting to warm the oil in the attachment. You could do this with the trailers, but I imagine it would take quite a bit of time.
     
  7. RobVG

    RobVG Senior Member

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    Yeah, the couplers ATCO posted would help but they are expensive. Our guys drag them down the road on occasion and they have to be replaced.

    The problem isn't warming up the oil- it's the fact that the oil is getting hot in the hoses coming out of the tounge causing expansion and creating pressure.
     
  8. Lashlander

    Lashlander Senior Member

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    We use the 6100 series Parker Quick Couplers.

    http://www.hydraulichouse.com/TOC/Hydraulic_quick_coupling.cfm

    Your right they are expensive though. Especially if they drag them around. The cheapest option would be to go to the hardware store and buy some new paint cans. Put an oil diaper in the bottom and pop the ball into it. Put the lid on and carry it in the truck. Solves the oil on the street problem.
     
  9. willie59

    willie59 Super Moderator

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    The more I think about it, I believe you might be right. You're saying you take a trailer out in the morning, drop it off, then come back later to pick it up, and have a problem making the connection to the lift gate line. Correct? There would be a small amount of oil in the line, and, if the cylinder is installed in a way that would leave the cylinder extended even just a bit, there would be some oil in the cylinder. As the oil warmed up from the days heat, the oil would expand, creating pressure, and even lift the gate ever so slightly. Pop the coupler and "thunk"...gate comes down. If all this is correct, I wonder if installing a small nitrogen charged accumulator in the line would help? In theory, it would absorb the pressure allowing you to connect couplers. Can't say for sure it would work, just a thought. :)
     
  10. Steve Frazier

    Steve Frazier Founder

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    I understand what the problem is, I have the same issue here. The oil expands when it is warmed and creates the pressure. What I was suggesting is to cycle the hydraulics before detaching to warm the oil in the trailer, so it is parked with warm oil and will actually create a vacuum when it cools. It works for me every time, but as I mentioned, it takes a while for the dump trailers to cycle. Might not be practical.

    By the way, my bucket develops so much pressure you can't depress the center of the coupling, I have to crack the fittings. The hose will stand out straight if you hold it a ways from the end.
     
  11. willie59

    willie59 Super Moderator

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    That's a neat trick Steve. ;) By adding warm oil to the cylinders, then allowing time for cooling, the oil will contract as it cools, taking away the pressure, and allowing you to re-connect the couplers. I'm wondering, though, if the mutiple drivers for RobVG could remember to do this each time. Forget one time and it's back to pressure on the coupler. :Banghead I haven't had to deal with this, it's an interesting problem.
     
  12. RobVG

    RobVG Senior Member

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    I see what you mean now Steve.

    ATCO, you understand the problem exactly. An accumulator would work but how much would it cost? I'll talk to our Parker rep and see if there is some kind of inline "bumper" I could use.

    I realized today that our trailers are now parked on fresh blacktop. This probably added to the problem.

    I was trying to think why our old trailers don't do this. I think it's because the rams on the old trailers leek.:D
     
  13. willie59

    willie59 Super Moderator

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    If I was to take a wild guess...I'd guess the way the cylinders are installed. The 1/2" line would have some oil in it that could cause the problem, but I'd guess the cylinders are installed in such a way that when the lift gate is all the way down it still doesn't have the cylinders fully retracted. Which, depending how far they are extended, could be a cosiderable quantity of oil remaining in the cylinders to expand. It's enough expansion to raise your liftgate a bit, that takes pressure.
     
  14. RobVG

    RobVG Senior Member

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    Well, I should wait untill after I look at it but the cylinders for the liftgates are vented- just one hydraulic line behind the piston. The weight of the gate brings it back down. The line for the liftgate and the line for the hoist are always full of fluid- fluid is trapped when they're disconnected.

    Your idea of talking to the manufacturer is a good one.
     
  15. willie59

    willie59 Super Moderator

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    Yes, I understand, you have single acting cylinders. They only have a hose going to one end of the cylinder. Here's what I'm getting at; fluid is pumped into the cylinder and begins to fill the cavity behind piston. The volume of oil is increasing inside the cylinder, so this forces the piston to extend the cylinder out until it reaches the gland and bottoms out. Now, you release the gate lever, this allows the oil to discharge from the cylinders and go back to tank. The weight of the gate forces the piston back into the cylinder. But...does it force the piston all the way back in until it bottoms out? That's what I'm getting at. If the piston doesn't bottom out, then there's going to be some quantity of oil in there to expand.
     
  16. RobVG

    RobVG Senior Member

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    Hmmm...

    Yeah but...

    The cylinders and the hoses are covered by a metal "hood". They don't get any direct sunlight. On the otherhand, the gate hose and the hoist hose coming out of the tounge are in the sun and are black. I think the sorce of the pressure is the hoses capped with quick couplers?
     
  17. willie59

    willie59 Super Moderator

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    I agree with all above. I haven't really encountered this problem, just trying to noodle through the thermal dynamics of it. We can assert it's a real problem by what Steve has experienced with his attachments. Are you having the same problem with the 1" line on the hoist cylinder?
     
  18. RobVG

    RobVG Senior Member

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    10-4
     
  19. willie59

    willie59 Super Moderator

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    Ahhhhh! Mystery of mystery's as to why your new ones do this and the old ones don't.

    Let's try a different solution. Typical wing style wetline couplers. They thread together so they can be connected with pressure on the lines. Parker and others make these style couplers as well.

    http://www.stucchiusa.com/PRODUCT SERIES/Wing.html
     
  20. RobVG

    RobVG Senior Member

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    I'll check 'em out tomorrow.

    This problem will shortly disappear- until next summer:)