Log splitter connections

   / Log splitter connections #31  
I don't have a backhoe, but my understanding is that they typically connect with three hydraulic lines: 1) inlet (high pressure from FEL power beyond), 2) PB (high pressure out to 3PH), and 3) outlet (low pressure to tank).

The arrangement described here lacks the low pressure return to tank. My sense is that it would be important to know the allowable pressure on the outlet port of the splitter valve (I've read that it might likely be in the 500 PSI range) and then figure out how much pressure might be generated by lifting the splitter with the 3PH.

-Scott

The powerhorse splitter is rated up to 3000 psi...per thier manual..Hyd lines need to be rated for 3k for both the inlet and outlet....If you have 3000 in you have 3000 out in a loop system....
 
   / Log splitter connections #32  
Theoretically, the IN and OUT ports should have the same psi rating, but the OUT port sees mostly low pressure, because there is nothing else before reservoir. If the OUT of the log splitter should go to the 3pt, then you would expect the log splitter to have whatever pressure the 3pt valve will allow, and this pressure is determined by the load on the 3pt assembly, and could be as high as 2500 to 3000 psi.
 
   / Log splitter connections #33  
Theoretically, the IN and OUT ports should have the same psi rating, but the OUT port sees mostly low pressure, because there is nothing else before reservoir. If the OUT of the log splitter should go to the 3pt, then you would expect the log splitter to have whatever pressure the 3pt valve will allow, and this pressure is determined by the load on the 3pt assembly, and could be as high as 2500 to 3000 psi.


J_J, thanks for the reply. Perhaps the psi rating on inlet and outlet ports are the same, but if this were true why are most tractor control valves plumbed for high pressure inlet, high pressure outlet (power beyond) to the next valve, and low pressure outlet to the tank?

I'm just trying to get it all straight.

-Scott
 
   / Log splitter connections #34  
Well, that is easy. If you order a valve that has the PB port as an option, then all fluid goes out the OUT port. After you install the PB sleeve, all fluid flows out the PB port, except the fluid from the work ports. and this is low pressure fluid going back to tank..
 
   / Log splitter connections #35  
Well, that is easy. If you order a valve that has the PB port as an option, then all fluid goes out the OUT port. After you install the PB sleeve, all fluid flows out the PB port, except the fluid from the work ports. and this is low pressure fluid going back to tank..

J_J,

Thanks again. I suppose that what I'm really trying to get at is why it is necessary to have PB at all, if a series of open center valves would work just as well. I think I've found the answers here:

http://www.tractorbynet.com/forums/hydraulics/116052-what-does-power-beyond-really.html

For me, the take home messages are:

- Open center systems operate at low pressure and high flow when all valves are in the neutral position

- System pressure builds when you move a lever and perform work with a hydraulic cylinder

- The outlet of an open center valve is designed to route hydraulic fluid from the work ports back to the tank at low pressure

Operating the 3PH with the splitter connected as desribed in this thread would subject the outlet port of the splitter valve to high pressure and could damage the splitter valve (perhaps a blown o-ring). I assume the arrangement works because the 3PH is usually only loaded with the splitter and lifting it does not generate pressure sufficient to damage the valve.
 
   / Log splitter connections #36  
Is is really okay to connect a log splitter ahead of the 3PH? This would subject the outlet port of the splitter valve to high pressure. My understanding is that outlet ports are designed for low pressure return of hydraulic fluid to the tank.

Several of the posts I've read on this topic say that only the last valve in a series (in this case the 3PH) should be without PB.

It's OK to do that, so long as you don't lift the 3PH while the splitter valve is connected. That way, you won't get back pressure on the return port of the splitter valve. You could just cap/plug the line feeding the 3 point, and connect the return from the splitter valve directly to the tank return line, to prevent accidental actuation of the 3PH.
 
   / Log splitter connections #37  
It's OK to do that, so long as you don't lift the 3PH while the splitter valve is connected. That way, you won't get back pressure on the return port of the splitter valve. You could just cap/plug the line feeding the 3 point, and connect the return from the splitter valve directly to the tank return line, to prevent accidental actuation of the 3PH.


Sort of defeats the purpose... You will want to lift the 3pt with the splitter to lower for large logs and then raise it to work at a comfortable height.

I have rear remotes with PB, The flow of fluid on the tractor...from the Pump to FEL (w/PB) to rear remotes (with PB) then PB is used to feed a loop with QCs, for log splitter (which can handle hi press in AND OUT) then to the 3pt hitch, and back to the pump / tank...

This is how the sytem works and is designed to work..
 
   / Log splitter connections #38  
   / Log splitter connections #39  
To reiterate...not all control valves have the same pressure spec in and out. My documentation says max pressure 2750 PSI, but it also says "Maximum Tank Pressure 500 PSI," which to me means no more than 500 PSI backpressure on the outlet side of valve...that can be easily exceeded in a PB circuit when using a downstream implement.
 
   / Log splitter connections #40  
The only fluid going back to tank would be from the return ports of each valve, and the output from the last valve in the circuit, and that is low pressure.

If the pump is running, and no valves are activated, there is very little or no pressure in the hyd circuit.
 

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