Thank you for the information.
Where can I find an explanation of the open center system?
Jobguy, you can find discussions of open-cneter systems througout this forum. That's how most of the hydraulic systems on our tractors work. Open-center systems allow the hydraulic pump to pump fluid at low pressure when hydraulics are not being used. The pump only needs to work under high pressure when you need to do work with the hydraulics.
In an open-center system on your tractor, you might have a 3-point hitch, FEL, and several remote valves. When you are
not raising or lowering the 3PH or FEL, there is no need for hydraulic pressure. Therefore, the fluid flows from the pump out to the FEL valve and then to the 3PH system and finally the remote valves. At the last valve in line, the fluid loops around and returns to the reservoir. If you need power to the FEL, the joystick valve closes off the loop and directs pressure to the FEL's lift or curl circuit depending on the joystick position. While the FEL is moving, the 3PH and remote valves do not have fluid because their flow in the loop has been interrupted. When the FEL joystick is again returned to neutral, fluid is again allowed to make the complete loop through the 3PH and remotes. In the phrase "open-center," the word "center" could be replaced with the word "loop" and it might be more meaningful. When anything in the loop needs power, it closes off the loop and uses pressure to do the work.
While doing work, if the load/pressure on the hydraulics becomes too great, the system has a relief valve that will open and return fluid to the reservoir to protect the pump and hydraulic plumbing. In our tractors, this is normally at 2000 to 2500 psi. This valve is the first thing in the loop so that any function of the hydraulic system is bypassed when the system overloads.
In the case of your remotes, when your remote valve lever is in it's center position, fluid just flows through it and continues on in the loop. When you pull the handle, one of the remote QDs is connected to pressure and the other one is attached to return. Putting the remote lever in the opposite position swaps the functions in the QDs so that the side previously connected to pressure is now attached to return and vice versa.
So in your system with only one hose attached, you can send pressure to the trailer to lift it by having only one hose attached. When you move the remote lever to the opposite position, the QD you have attached will be connected to the return side to the reservoir allowing the trailer to lower, but the other side of the QD will be under high pressure because nothing is attached. That closed connection will cause your hydraulic system to go to its highest pressure and open the relief valve. The relief valve will stay open until the dump trailer lowers and you put the remote valve back into the center position to allow fluid to again start looping in the system. Therefore, before the relief valve opens, you will hear the engine go under load and remain under load until you return the remote to neutral.
Opening the relief valve occurs often when we use our FELs on our tractors, but we normally immediately back off and move the joystick so that the relief valve closes and pressure is return to normal. With your dump trailer, you will keep the system in relief for much longer and the relief valve could get hot and heat up your hydraulic fluid if you did this continually. With the intermittent use of your dump trailer, I don't think you will notice any problems, but you might be curious as to why your engine seems to be working hard when you are only lowering your trailer. Now you know.
