3 spool directional valve not working

[kiotiken]

I have a 3 spool valve on my firewood processor. Valve 1 lifts and lowers the splitting head, valve 2 controls a hydraulic clamp and valve 3 controls a hydraulic motor that turns rollers to advance the log. Valves 1 and 3 no longer work in one direction, valve 2 seems to work normally. I can raise the splitter head or advance a log normally but it's extremely slow to lower the splitter head and I cannot reverse a log (maybe a few inches). There's no pressure registering on the main pressure gauge in that direction. Here's the valve I'm using:

MD3 3-Spool Directional Control Valve | Princess Auto

I'd appreciate any ideas

Thanks!

 

[Dave M7040]

Did this setup ever work properly or are you just now trying to get it operational?

Details about the pump.

Dave M7040

 

[kiotiken]

I build the machine about 6 years ago. It's worked well up until this week. Both spool 1 and 3 failed together. The pump is this 2 stage log splitter pump 28 GPM Dynamic 2-Stage Pump | 2 Stage (Log Splitter) Pumps | Hydraulic Pumps | Hydraulics | www.surpluscenter.com.

Thanks.

 

[/pine]

Is there any QD's in the system ?

 

[kiotiken]

Is there any QD's in the system ?

No, none. Fairly simple set up. 2 stage pump to 3 spool power beyond valve. Log splitter valve on the power beyond circuit. Goes through a rad, filter and back to tank.

 

[Dave M7040]

In looking at the valve spec's on the Princess Auto site I notice two details.

All spools incorporate internal load check valve to lock cylinders in position.

The spec's make reference to a "Motor" spool as an option.

Does the literature on the hydraulic motor you used make any mention of valve spool requirements and load checks?

If possible, I would be inclined to remove the outlet or tank hose from the valve and direct it back into the reservoir so you can watch the flow coming out.

If you have lots of flow perhaps your two stage pump is not switching to the high pressure stage.

With a simple system either the pump is not working properly or the valve has internal damage and is bypassing fluid back to the reservior.

You comment on not seeing any pressure readings on your gauge.

Dave M7040

 

[kiotiken]

OK, thanks Dave. I'm going to have to say the pump is still switching to high pressure since it's still pushing large blocks through the 6 way head. I just called Princess Auto and they told me they'd either replace the valve or "make it worth my while" to bring it back. I'll take it apart and go into PA tomorrow. He thought I blew a ring in the valve but couldn't say how two spools could fail at virtually the same time.

 

[Dave M7040]

I did not initially understand you had two valves in your system and the downstream one was working properly.

That narrows the culprit down.

Talk to Princess hydraulics guy about you running a motor on one spool.

Dave M7040

 

[kiotiken]

Do I need to run a motor spool if I have a motor on the circuit? Will it cause issues if I don't? My understanding was that it allows for finer control. I don't really need fine control, it's mostly full speed ahead. Can I convert one of the spools to be motor control and leave the other two as cylinder or would I need a separate motor valve?

 

[Dave M7040]

Not all hydraulic motors have the same requirements in terms of how they are controlled. Some need case drains and others do not as one example.

One issue with motors not experienced by hydraulic cylinders is when the valve returns to the center position the motor is instantly stopped. The sudden stop produces pressure spikes for both the motor and valve.

In trying to imagine what might have gone wrong with your valve, I wonder if the non motor spool together with load checks might have not been a good combination.

Best to provide Princess with all the facts as they have technical resources from the manufacturers

Since a motor spool is mentioned as an option in the spec's for your existing valve you may not need a separate valve for the motor.

From the internet:

If you want rotation speed of motor to smooth, predictable and repeatable, use the correct valve. Cylinder spool: work ports blocked in neutral. Motor spool: work ports connected to tank in neutral.

Dave M7040