Blowing out o-ring, stumped, need help!

[Venturabass]

I have a brand new Kioti DK5310SE tractor I just bought this year. I also have a Woods TSG50 stump grinder. I've had two incidents now where I was about two hours into stump grinding, and upon repositioning the tractor and lifting my 3 point hitch, I've blown out an oring on the tractor's rear remote. The oring seals between a side cover plate and the rear remote. It's been to the dealer twice and covered under warranty. The first time they found one of the cover plate bolts was loose. The second time that was not the case, but in each it appeared the oring had been forced out. They've had the rear remote valve off and have mic'd the gland where the oring sits and are telling me it's all to spec. Now they're looking at me as if there's something off about how my stump grinder is plumbed. I've talked to a few other dealers, and Woods Equipment, trying to figure out what the issue might be. Hoping a hydraulic expert on here can help, as it sure is frustrating. I'm afraid to use the grinder again, thinking I need to come to the bottom of this so it doesn't happen again. Here's some details and photos on the setup.

Tractor Hydraulics

• Your typical open center system with a tandem pump and dual hydraulic circuits in parallel. For the main circuit, fluid flows from:
  • Hydraulic filter
  • Pump
  • Hydraulic block - routes fluid to the front end loader, and also 3rd function valve (which selling dealer installed during sale)
    • Also includes the main relief valve, set at 2700+ psi from factory.
  • Rear remote valve
    • The valve is a detent type, and uses a single set of quick connects to send hydraulic fluid to your implement.
  • Rear lift valve
  • Sump

Stump Grinder Hydraulics

• Has two dual acting hydraulic cylinders, but only 1 inlet and 1 return hose. To accomplish this:
  • Hydraulic fluid runs from the tractor's rear remote valve, to a Prince monoblock, two spool directional control valve. This is also open center and the spools are spring return to center.
  • Stump grinder valve is rated as at a nominal 8 gpm, tractor's main pump is rated at 9.6 gpm.

How To Operate/How It Fails
Let's see if I can explain this.

• Back up to a stump.
• Lower the 3 point hitch and stump grinder frame to ground.
• Start up PTO.
• Take the lever for the tractor's rear remote valve and move into the flow position (detent) to start hydraulic flow to stump grinder.
• Now fluid is flowing to the two spool valve on the stump grinder.
  • Use 1 spool to raise the grinder head to the the right height.
  • Then use the 2nd spool to pass the grinder head left and right, grinding while you're doing this. Mind you this is a very slow process. You feather the grinder so it doesn't buck and kick in the stump.
  • After each pass, lower the head and repeat.
• Eventually you've ground deep enough into the ground, and it's time to reposition.
  • Retract the grinder head cylinders so it lifts the head off the ground.
  • Put the tractor's rear remote valve lever back in neutral. This stops flow of fluid to the implement and will now allow use of 3 point lift.
  • Lift implement with 3 point hitch.
  • Reposition tractor to stump.
  • Lower hitch and repeat the whole process.
• Both times the oring has blown out, it's been about 2 hours into this series of events.
  • Eventually I'll go to lift the 3 point hitch, and one of the 3 or 4 orings that's sandwiched between the tractor's rear remote and this side cover plate will fail, and hydraulic fluid will come spraying forcefully straight backwards out the tractor from this flange.
  • Once this happens, if I take my hand off the 3 point hitch lift level, the spraying will stop, but a continuous stream of hydraulic fluid will start pouring from the flange as long as the tractor is running.

In talking with Woods Equipment the only lead I've gotten so far is that they'd prefer that I run the hydraulics from the tractor's rear remote valve to a selectable valve to send the hydraulic fluid to either one of the grinder's hydraulic cylinders. Then I'm using the tractor's rear remote valve to actuate the cylinders on the stump grinder. They had concerns that I'm already sending fluid through the tractor's valve (which is held open 100% with the detent, and then it's going through another valve rather than just an open passageway if I were to use a selectable valve.

I bought the stump grinder used about 4 years ago. It was the previous owner that took the selectable valve from Woods off and installed the 2 spool valve.

The point Woods made was that it wasn't so much as I was building up too much pressure with the setup I'm running, but that I'd be creating a lot of excess heat, and for whatever reason I'm finding the weak point of failure on this model. And no I'm never hearing the relief valve open or the engine bog.

Can anyone help corroborate or explain the proper hydraulic setup and why what I'm running doesn't work? Photos below.

Tractor, you can see the single set of hydraulic quick connects, this is where I connect the stump grinder to.

Here's the stump grinder. You can see the two cylinders, two spool valve, and the inlet/outlet line I plug into the tractor.

Here's a close-up of the two spool valve on the stump grinder.

After oring failure, you can see the constant stream of hydraulic fluid. It's coming from this cast iron cover and the side of the tractor's rear remote valve.

From the service manual, this is a better view of what the rear remote valve(s) and that cover look like. There are 3-4 orings in there.

 

[oldnslo]

Will Woods supply you with a schematic of what they recommend for operating this stump grinder. Yes heat can weaken seals but curious what the Woods system would do to produce less heat.

Is it possible your three point tries to keep lifting after fully raised? I.e. feed back linkage needs adjustment?

 

[mrmikey]

Can't see how it would generate too much heat unless you're way over the flow rating of any of the pieces which you are a bit for the grinder valve. Get a non contact thermometer and check the temps, don't guess. You should be able to hold your hand on any component, not for ever but you should be able to touch it gently.
You're not deadheading the cutter wheel when you shut it down, i.e. closing the valve when it's still rotating? The pressure relief is not set too high? Wrong size/profile/material O rings? Return line obstruction causing back pressure? The block sealing surface is flat? Bolts are torqued to the correct specs (maybe change them out for a gr8 bolt and flatwasher to preclude any possibility of stretching).
Not knowing the actual specs of the machine but 2700psi seems high to me but it could be correct, just throwing it out there. I don't doubt shock load is a lot higher than that......M

 

[KWentling]

I too would question if the correct O-rings are being used and if the bolt torque is correct. Those should probably be Duro 90 O-rings. Most generic kits are only Duro 70. I would hope the dealer is using the Kioti O-rings for that application.

 

[ArlyA]

If the correct O-ring is being used and bolt torque is correct, I'd guess you have some poor machining where the o-ring is which allows its premature failure.

 

[Venturabass]

Will Woods supply you with a schematic of what they recommend for operating this stump grinder. Yes heat can weaken seals but curious what the Woods system would do to produce less heat.

Is it possible your three point tries to keep lifting after fully raised? I.e. feed back linkage needs adjustment?

I can check with Woods but per my convo with them they just recommend I install their delectable control valve on the grinder (which does nothing more than send fluid to either one of the cylinders but not both) and then plug that into my rear remote on the tractor and use that for feathering flow control. Doesn’t seem much different than the way I’m doing it but they think that going through the tractors rear remote and then a second flow control valve is making it too hot.

I don’t think the 3 point continues lifting. Per the manual and as observed you can only control the rear remote or rear lift. But not both at same time. And when I take my hand off the lift it stops moving and you can hear the engine relax as it’s not reacting to lifting the load.

 

[oldnslo]

Is that stump grinder heavier than it looks in those pictures? Does not look heavy enough to make a 50 HP tractor grunt to lift it. If 3 point is straining enough to bog engine then you definitely have the pressure to blow seals if anything in the seal style or cavity is not correct.

I looked on Woods website and it showed weight of approx 550 lbs so that should not strain your 3 point. Sounds like an issue with how 3 point works if straining engine to lift this stump grinder.

Agree on how not sure changing plumbing per woods would reduce heat.

 

[Venturabass]

To answer some questions:
Just to clarify the hydraulic flow is only for swinging/raising the cylinders that position the cutter head. The tractor's PTO turns the head to perform the grinding.

Yes the grinder is only ~500 lbs, not nearly enough that it should cause a problem.

According to what the dealer told me after the 2nd time it blew out:

• Each time the oring looked torn apart, as if it were forced through the joint.
• They took the valve off and measured all the surfaces for flatness (and supposedly gland depth). Those were all within spec.
• It sounded like the second time they actually ordered an o-ring kit, and it was "the same" as the last time.
• They did throw around whether the oring that was in there the first time had the right durometer rating. They mentioned something fast about 70 to 90 durometer, but I didn't follow at the time as to what that oring should be, only that, it's the correct oring going back in.

If you look at the photo of the book diagram above, the rear remote valve is machined on both left and right sides, and is bolted (sandwiched) to the transmission case on the inboard side and with that cast iron cover on the outboard side. Each machined face looks like it has 4 orings, but it's the same oring that's blown out both times, and the fluid shot straight out the back each time. Intuition tells me there's something wrong with that one oring gland that the dealer is missing. Otherwise why that joint, why that oring, and assuming on spray pattern it's that one side of the gland that's bad? Until dealer confirms that they won't start replacing parts.

Also....
I found Michigan Iron & Equipment on the forums and spoke to someone in their technical group this morning. What intrigued me was they're a Kioti dealer (so they should know Kiotis), and they manufacture/sell their own hydraulic setups and even custom jobs (so they should really know hydraulics right?).

Well despite what Woods told me, and of course without seeing my setup, there should be NO PROBLEM running the rear remote, to a 2 spool monoblock directional control valve, as long as it's configured for open center (which I verified).

They had two tips where they would look:

• They have seen depending on length, that the 3 point hitch is capable of dead heading where the top link is too long, and the lift lever will keep moving back, but the cylinder won't lift. I'll give that a test but don't think it's the issue as each time it's blow I lifted from rest on ground, and it was as soon as I cracked that valve.
• Second is that there is a blockage or something with the system that is causing a backpressure due to flow interruption.
• The difference between the 8gpm on the grinder's valve vs. the 9.6 gpm on the tractor shouldn't matter. After all I'm limiting flow so little when I swing the cylinders, that 95% of flow should be bypassing the grinder and going right back to tank.

Needless to say, my next step needs to be to hook it all back up, start using, and SEE WHAT HAPPENS. And if it fails, BRING the grinder with me to the dealer to check pressures. Fingers crossed. I really don't want another trip back to the dealer...or more downtime.

 

[oldnslo]

Were you at the dealership when they measured everything? Tolerances on gland depth is typically around .002 inches or two thousands of an inch. Parker hand book has gland dimension information based on cross section of O-ring and if static or dynamic seal. Reason for asking is what did the dealer use to check gland depth? Durometer might make a little difference but in this case 99% of the seal is based on metal to metal contact between the two surfaces. The seal is just there to fill in imperfections. Other thing to check is surface finish. No nicks burrs scratches etc. It does not take much of a burr or nick to cause a leak. Blown seals are typically caused by surfaces not being flat or clamped tightly together.

Best wishes on solving this issue.

 

[ArlyA]

Were you at the dealership when they measured everything? Tolerances on gland depth is typically around .002 inches or two thousands of an inch. Parker hand book has gland dimension information based on cross section of O-ring and if static or dynamic seal. Reason for asking is what did the dealer use to check gland depth? Durometer might make a little difference but in this case 99% of the seal is based on metal to metal contact between the two surfaces. The seal is just there to fill in imperfections. Other thing to check is surface finish. No nicks burrs scratches etc. It does not take much of a burr or nick to cause a leak. Blown seals are typically caused by surfaces not being flat or clamped tightly together.

I'd test it out without yoru grinder on. I'm in agreemant with old, it might be the tractor, not the implement.