problem with hydraulic unit
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  1. #1
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    Default problem with hydraulic unit

    This is the hydraulic unit I'm having trouble with, from my K.O. Lee surface grinder.



    The history is that I ground a part and then left the area of my grinder leaving the spindle and hydraulic system powered up and running. I came back some time later and smelled something hot. I also noticed a big puddle of hydraulic fluid all around the machine. I turned everything off and cleaned up. After, I turned the hydraulic unit back on. It runs like it used to for a few seconds and then a bad noise starts. I don't know if this noise is entrained air, fluid cavitation, or a relief valve cracking. All of those things make noises.

    Here is a short video clip. Turn up your sound and you will be able to hear the sound of the machine starting up, as the noise goes from normal to not-normal at about 0:14. Any idea what this noise is, or why fluid may have leaked when the pump got hot?

    metalmagpie

    http://nwnative.us/Grant/images/temp/hydStartup.mp4

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    After you lost all of that fluid, did you fill the tank back up?

    Pete.

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    Yep, sounds like it ran out of oil, sucked the tank dry. Maybe the inlet is clogged and the flow can't keep up with the pump. Teardown time. Did you find where the oil escaped and fix that issue? There may be an internal leak that is allowing the fluid to escape the system. Need to hunt that down first. Should never be able to get out in that kind of quantity.

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    Quote Originally Posted by Mr_CNC_guy View Post
    After you lost all of that fluid, did you fill the tank back up?

    Pete.
    I guess all that fluid on the floor and the hot smell freaked me out enough so I wasn't thinking. I topped up the tank (took about 2 gallons) and now no more bad noise.

    Still wondering what caused my machine to vomit 2 gallons of hydraulic fluid on my floor. And I'm really grateful for those oil absorbent pads (diapers). As I'm learning my way around this finicky hydraulic unit, they are coming in oh so handy.

    metalmagpie

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    eKretz is correct, you need to figure out why / where the oil came from or in the middle of a grind it might happen again and you will screw up a good part. Have you ever cleaned out the tank and tank strainer? Is there a pressure side oil filter? Could you have over filled the tank ? Was there oil on the top cover by the motor and pump?

    I would think you could repeat the problem and sit there and watch. If the machine uses hyd. oil to lube the ways, maybe a drain hole at the end of the ways plugged up with swarf and it flowed out? You need to trouble shoot this or you may ruin the pump and cost you big time.

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    Finally started working on this unit. On my grinder, the hydraulic unit sits in the base. Hard to get in and look at things. Anyway, I took all the hoses off and removed the unit from the base.

    I found that the discharge hose from the main table valve had come completely off, probably when I moved the machine. K.O. Lee used screw type radiator hose clamps on its drain tubes. This one was attached in a place it would be devilishly hard to get to with a screwdriver. So it probably wasn't tightened enough. I replaced that clamp with one with a hex head that I could tighten by reaching up there with a ratcheting wrench. I believe it is now once again securely fastened to the valve body. I am hopeful that this will solve the leak problem.

    I'm going to replace the pressure hoses and intake filter while I'm at it.

    And I'm going to try to get by without tearing the pump down.

    metalmagpie

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    You may have burnt up the shaft seal from the lack of oil, try globbing a couple of finger fulls of new grease at the pump shaft area to see if it’s sucking air thru the shaft seal. Opening up that Barnes pump will be a pain as there are no replacement parts for those, a shaft seal can be matched with a generic but they use a thin clear gasket for the housing sealing. I’m thinking it’s quiet for the first 13 seconds cuz the shaft seal allows the oil in the pickup tube to settle back down the tank when off. On startup it takes 14 seconds to prime itself and air entrainment will be the noise cuz of the bad shaft seal. That’s my two cents

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    Quote Originally Posted by e-fishin-c View Post
    You may have burnt up the shaft seal from the lack of oil, try globbing a couple of finger fulls of new grease at the pump shaft area to see if it’s sucking air thru the shaft seal. Opening up that Barnes pump will be a pain as there are no replacement parts for those, a shaft seal can be matched with a generic but they use a thin clear gasket for the housing sealing. I’m thinking it’s quiet for the first 13 seconds cuz the shaft seal allows the oil in the pickup tube to settle back down the tank when off. On startup it takes 14 seconds to prime itself and air entrainment will be the noise cuz of the bad shaft seal. That’s my two cents
    Thanks for your input! I believe that my pump consistently pumped fluid up to the table control valve, and that the return line from the valve being disconnected, just pumped my fluid all over the place. So I don't think the pump burned up anything. In fact, after I refilled it I used it to grind several parts and the pump sounded and behaved just like always. It does get hot after awhile, and I believe that this is a symptom of wear in a gear pump. I am corresponding with another guy with the same machine, and his hydraulic pump gets hot too.

    metalmagpie

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