control valve squealing on stand up skid steer

[liljohnuser]

I recently installed to new directional control valves on my skid steer "little jon lg500" made by JLG.the valves i installed are prince rd 2500 they were bigger then the original valves but the closest i could find. machine works good forward and backwards but squeals when i try turning or reversing there directions. I had to downsize the work ports from 1/2" to 3/8 and the in and out ports from 3/4" to 3/8". i am hoping thats not my problem. If it is i have some valves for sale.

 

[SSdoxie]

The Prince valve is bigger in what way? Larger in body, casting size? or rated for more flow? If it was rated to handle more flow, I would think the port sizes would be the same or larger. Reducing fittings from 1/2" to 3/8" reduces the opening 45%. Going from 3/4" to 3/8" reduces it 75%, so only allow 1/4 of oil flow at same pressure as the original valve.
Going in a straight line takes less working pressure at the motor than turning. Going straight both motors work together, but turning each motor is working against the other so pressure is almost if not more the double.
Where is the relief valve for the drive system? If at the inlet of the valve, you could be seeing much higher pressure at the pump than at the relief valve due to the restricted (3/8" fitting) at pump inlet.
To identify if restriction pressure added to normal working pressure is too high. Use 2 identical gauges, put 1 at the outlet of the pump then 2nd at inlet of the valve, work the machine until the squeal starts and compare the pressure. If they are the same, move second gauge to a work port and repeat the test. When the gauge at pump reads higher than 2nd gauge will identify if and where there is restriction.

 

[J_J]

Why did you install log splitter valves/

Are you using them in a CC or OC hyd system?

Yes, the flow on those valves are about 25GPM.


If using them to turn, use 1/4 lever on both, and don't go into detent

http://www.princehyd.com/Portals/0/valves/ValvesLsRD25.pdf

That is not a good valve for controlling motors.

Two of these would be a better choice.

Surplus Center - 1 SPOOL 8 GPM PRINCE MB11C5C1 MOTOR SPOOL VALVE

http://www.surpluscenter.com/item.asp?item=9-7975&catname=hydraulic

What valve was was used when new?

 

[liljohnuser]

I took the original valves to a local hydraulic shop that has been in business for 2o years and they said they never seen anything like them before couldn't identify the manufacturer. the ports went out the front and bottom nothing on the sides they were about half the size of the ones i installed.
I explained to baileys what my situation was sent them some pics of the originals and they suggested the ones i used. I wish i would of seen the valves you suggested they have the same size ports as the originals I probably cant return the valves now that I installed them. hope i don't have to dish out another $200+.

 

[J_J]

TANDEM CENTER VALVES

Tandem center valves when in a neutral position by passes the flow of hydraulic oil to the return line. This is used to hold the cylinder/piston in position with no load on the pumps. When this system is the pump is running constantly to keep a ready supply of hydraulic oil, but as long as the cylinder/piston is not in operation the pump is working under no pressure or load. This system keeps wear and tear on the pump down to a minimum.

OPEN CENTER VALVES also called motor spool valves

Open center valves are the same as the tandem center, except that in the neutral position all lines are connected back to the reservoir. The primary use of this system is to prevent "shock" loading when the valve is placed in neutral. This takes pressure off the motor. This system is used in situations where the operating device needs to be moved by hand.


CLOSED CENTER VALVES

This type of valve is used in a hydraulic system where the valve blocks the flow of oil from the pump into an accumulator. The accumulator (see below) is used to store the oil under pressure. This valve takes the pressure off the pump and in neutral locks the cylinder in place with no load on the pump.

If you have to use tandem center valves in a motor circuit, then place a relief valve across the in out ports. When the pressure gets to the relief pressure, the fluid will just recirculate with in the motor.

Even using tandem valves, if you slowly decrease the flow, you can shut down the motor safely.

 

[liljohnuser]

the valves are actually Prince part number RD-2575M4ESA1 Bailey part number 220-107 they are spring to center open circuit 4 way 3 position.
In your honest opinion should I ditch these and get the ones you suggested. would the reduction in fitting size cause the squealing.
And do you know if the handle is removable on the valve you suggested so i can hook up my linkage.

 

[J_J]

I looked into the valve a little more, and your valve is used to control a hyd motor. In neutral, the ports are connected to tank.

Is that valve a single or a double spool valve. Otherwise do you have one valve or two valve.

I believe the relief was set at the factory to 1500 psi. Did you reset the relief pressure.

How are the valves plumbed, in series or in parrallel?

If your hyd system is open center and you have these valves in series, both valves can use half of the flow or any part of the flow.

But,

If you are using the OUT flow on the first valve to feed the second, there is a 150 psi rating on the OUT ports of those valves.

If the valves are plumbed in parrallel, they both share the flow.

Way to tell if the valve is CC is to install a gage in the IN port in a tee and monitor the pressure.With the valves in neutral, the CC circuit will have pressure, and OC will have no pressure.

The instructions say that the OUT port from each valve must go to tank.

Do you have the parts list for your machine? If so, what is the original steering valve number and brand.

http://www.princehyd.com/Portals/0/valves/RD2500InstS.pdf

The squealing is not normal except when the relief is activated, something is not rightt.

 

[Gordoninvt]

This seems to be a very common problem with these machines.
#1 The Little John does NOT use "Hydraulic oil" for it's hydraulic supply. Rather it uses SAE 10w30. This was found by a member of my little_john_rocks yahoo group in the troubleshooting section of the manual I set him up with. It reccomends that if you have low forward back moving power to switch from the 10w30 to 10w40. I changed mine twice before finding out I was using the wrong oil.

#2 From my personal experience chain tension plays a role in power at the wheels. The manual shows proper deflection along the bottom most run of chain as being only 1/4" Since the chain changes direction so many times I am convinced it makes a huge difference if your chain is very loose. More power with both wheels turning at the same time rather than the chain binding.

#3 JLG sold to another company shortly after LJ was built and the new owners concentrated on the big lifts.
The company that does at least try to help is Manitex. So far no luck but they will know the machine.