Hydraulic lock valve issue

[Dadnatron]

I have a Chinese import articulated flail mower which has been working fine, but I have a new issue.

The hydraulic lock valve on the main 'raise/lower angle' cylinder began leaking and a fitting broke. I have always hated how this was setup, floating on nothing but the connections to the cylinder, but it was working, so I left it.

Apparently, the raising and lowering caused stress on the tubing connection just as it connected to the lock valve and when I was messing with it, it broke completely off. Basically, the connection is exactly like you see remaining connected. it is a metal connection to the cylinder, with a very short rubber hose (to allow for flex) then another metal connection leading to the valve. It is the connection right at the valve which broke.

Anyway, I need either another piece of the metal/rubber/metal connector to reattach or I need a completely different type of connection to better attach the lock valve to the cylinder.

Any ideas on either where to get another or how to connect it better/more stable? That valve just floats on the 2 connectors, as designed... its just not a GOOD design.

 

[Dave M7040]

That lock valve looks like a previous owner add on and not part of the original design.

Do you even need it with a cylinder in good condition?

Three point hitch hydraulics usually incorporate a relief valve and a safety valve. The relief valve limits how much you can pick up.
Once the load is lifted, the hydraulic fluid is lock in and the relief valve does nothing should you add more weight to a raised implement as an example.
.
The safety valve bleeds off pressure generated when a load is bouncing on the 3 pt hitch and its setting is much higher than the relief valve.
The safety valve is set using a fuel injector tester so not a do it yourself task.

Most loaders do NOT incorporate a safety valve. Often owners who add forks to their FEL end up breaking expensive parts because the added leverage generated by the forks has no where to go and things break.

I suggest you look at your articulating flail in the safe light.

Dave M7040

 

[Dadnatron]

Honestly, I don't know. It came like this from the factory. I am not sure whether the valve only locks or allows for the flail to 'float' after a given pressure is overcome.

I've never liked the connection for this reason, but whether or not I can simply do away with it is beyond my level of 'expertise'. The hoses connect directly to my tractor valve, so I would suspect they would hold pressure fine.

I'd love to toss it on the 'spare parts' shelf, but I certainly don't want to do that if it is integral in the safe function (ie, I won't tear it up) of the machine.

 

[Dave M7040]

Honestly, I don't know. It came like this from the factory. I am not sure whether the valve only locks or allows for the flail to 'float' after a given pressure is overcome.

I've never liked the connection for this reason, but whether or not I can simply do away with it is beyond my level of 'expertise'. The hoses connect directly to my tractor valve, so I would suspect they would hold pressure fine.

I'd love to toss it on the 'spare parts' shelf, but I certainly don't want to do that if it is integral in the safe function (ie, I won't tear it up) of the machine.

Do you have a manual you could post?

Dave M7040

 

[ovrszd]

Stuff like this bothers me. I'd have to build a bracket to securely hold the lock valve to the cylinder barrel. Maybe using some sort of barrel clamp with a flat bracket. Use the two holes thru the body of the valve?

As to the fittings. They appear to be standard stuff. Unscrew the fitting from the valve and the banjo bolt from the cylinder. Go to your friendly tractor dealership and find fittings that fit each end, eliminating the steel portion, building a short hose??

 

[Dadnatron]

Do you have a manual you could post?

Dave M7040

LOL.... HA HA HA HA ha ha ha ha .... heh.... Manual......

 

[ericm979]

I think it's either a pilot check valve or a crossover relief or maybe both combined in one. The hex sided things on each end look like adjustable relief valves. Those would (hopefully) prevent damage to the mower head from overpowering it with the hydraulics.

Pilot check valves would keep the cylinder from "bleeding down" due to leakage past the valve on the tractor. They are common on hydraulic 3pt top links. They don't allow float so if it floats then the valve doesn't have checks.

The fix would be to get new longer hoses made to run from the mystery valve to the cylinder. That would allow you to mount the valve solidly to the cylinder using hose clamps or a fabricated bracket. They spent the $$ to put it on so I would lean towards making it work rather than removing it.

 

[ericm979]

Here's one that has what looks like a check valve: VL-AGL Silver & Gold Ditch Bank Flail Mower |
This one touts a floating tilt and does not have a mystery valve on the tilt cylinder: VL-AGF Gold Ditch Bank Flail Mower |

The hoses for the mystery valve to the cylinder probably cost about the same or a little more than the fittings to remove it entirely and run your hoses directly to the cylinder.
OTOH if you have a float-capable remote valve, and the mystery valve is a check valve, removing it would get you float.

 

[Dadnatron]

The fix would be to get new longer hoses made to run from the mystery valve to the cylinder. That would allow you to mount the valve solidly to the cylinder using hose clamps or a fabricated bracket. They spent the $$ to put it on so I would lean towards making it work rather than removing it.

I tend to agree with you Eric.

The hoses are long enough that a cylinder mount would not be an issue. Clearance is the only issue, but I suspect I could position it somehow without too much difficulty. I'd just need to find/fab some brackets/clamps for the attachment.

I'm not sure why they used/needed the banjo bolts rather than just short hoses from the cylinder to the valve. Other than not actually mounting the valve somewhere, I don't really see the need for the bolts rather than just a short hose from the valve to the cylinder. If I clamped the valve to the cylinder and attached short hoses from the valve, do you see any reason it wouldn't work? (If physically I have clearance and slack for main hoses?)

 

[ericm979]

The banjos might act as flow reducers so the thing does not move too fast. It's a small diameter cylinder which would move fast if not restricted. If you run fittings into the threaded holes in the cylinder you could put reducers in the fittings (the ones that are basically washers with tiny holes which go inside fittings) or add a needle valve or valves to the circuit somewhere. You could even put that on the tractor end of the hose by the quick connect since room is tight on the mower.

 

[BukitCase]

If that picture is the way the unit came, it looks like the cylinder itself is plumbed as a single action ("raise, or NOT raise) - only way that could work with a double action circuit is if that crappy valve hanging in the wind is some kind of pilot operated check valve??? IOW, is that second port on the cylinder itself actually BLOCKED, or am I missing something?

Both of my tractors' hydraulic toplinks have a check valve, but it's HARD plumbed BETWEEN the two ports of the cylinder, and wouldn't even be necessary except for valve leakage control. Works as is, if that changes I'd probably just bypass it.

More confused than usual... Steve

Nevermind, took a third look, guessing the UPPER bolt head in the pic USED TO BE the second connection...

 

[oldnslo]

Dadnatron
Are there any part numbers on the valve assembly? If yes post them and then maybe someone can identify what that valve assembly is.

 

[Dave M7040]

I think it's either a pilot check valve or a crossover relief or maybe both combined in one. The hex sided things on each end look like adjustable relief valves. Those would (hopefully) prevent damage to the mower head from overpowering it with the hydraulics.

Pilot check valves would keep the cylinder from "bleeding down" due to leakage past the valve on the tractor. They are common on hydraulic 3pt top links. They don't allow float so if it floats then the valve doesn't have checks.

The fix would be to get new longer hoses made to run from the mystery valve to the cylinder. That would allow you to mount the valve solidly to the cylinder using hose clamps or a fabricated bracket. They spent the $$ to put it on so I would lean towards making it work rather than removing it.

Cross Over relief valves only work with two equal sized cylinders. Two angle cylinders on a plow or two swing cylinders on a backhoe. The valve needs to be able to move fluid from one part of the hydraulic system to another of equal volume. With a double acting cylinder, the volumes on either side of the piston are not equal and the valve cannot work.

Dave M7040

 

[ericm979]

Thanks Dave. I used the wrong word, I'd been thinking of a valve like this:
1/2 NPT 3 GPM 15-3 PSI Hydraulic Cushion Valve | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
because of the adjusting nuts on either end.
But maybe they're for adjustable check valves.

 

[Dave M7040]

Thanks Dave. I used the wrong word, I'd been thinking of a valve like this:
1/2 NPT 3 GPM 15-3 PSI Hydraulic Cushion Valve | Relief & Cushion Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
because of the adjusting nuts on either end.
But maybe they're for adjustable check valves.

Eric
I looked at the Prince valve and believe the same issue applies:.

Brand new PRINCE DRV-4HH. Cushion valve or double relief valve. Use to stop or minimize surge, shock and overload in hydraulic circuits. Install between control valve and motor or cylinder. Bypasses to opposite side to prevent cavitation.

For this type of valve to work it has to have somewhere to send the over pressured fluid that that can accept it. With the control valve for a double acting cylinder in its neutral position, the fluid is locked in the cylinder. Because each half of the double acting cylinder contains different volumes of fluid, no exchange between opposite side of the cylinder piston can occur.

I still wonder if someone added this valve to the implement not understanding its specific application

Dave M7040

 

[ericm979]

Is the cushion valve intended to work when the control valve is not in neutral? I.e. when you're extending or retracting a cylinder. If the cylinder pressure is too high because the stuff attached to the cylinder is running into something, then the cushion valve would send fluid to the other side which would be open to tank through the control valve. I've seen people use cushioning valves like this on backhoe thumbs. But yes you're right it would not do anything when the control valve was in neutral closing off the work ports.

(well maybe it might but only in one direction due to the rod side volume being smaller than the piston side volume. If the control valve is closed and something is extending the cylinder hard enough to trip the relief in the cushion valve, fluid could flow through the cushion valve relief from the rod side to the piston side. But as you pointed out it wouldn't work the other way.)

I'm probably wrong about it being a cushion valve and it's a two way adjustable check valve. If it is and you want float (and your control valve has float) it could be removed.

 

[Dave M7040]

When the control valve is anywhere but its neutral position then the control valve's relief valve is in the circuit protecting things in one direction and in the other direction, fluid can easily return to the tank.

Remember that fluid is in-compressible so for any fluid to change sides in a cylinder, that cylinder's piston has to move.

With a power angling blade, when you hit something on one side, the cross over relief allows the blade to move away from the object being hit. It is not just a matter of fluid moving but cylinders moving.

Dave M7040