closed center / open center

[PutnamVictor]

The pump is a Sundstrand with separate outputs and returns for motion and implements. I want to abandon both the ports for the implements. So, if the implement spool is a "closed center" then I should be able to plug up the pressure and return ports coming from the pump without damaging the pump, is this correct? Now if it's a "open center", will a line from pressure to return work? Will it need some back pressure to work?

To verify it the spool is open or closed, could I use 50-100lb of air on the pressure side?

 

[Soundguy]

if valve is OC.. it should flow from in to out port when the spool is in neutral position. if if an oc valve, then the in / out will need to be plugged together so pump won't deadhead.

soundguy

 

[J_J]

Any of these pumps look similar. Is is a gear pump or a variable speed pump.

Do you have a model number?

Sundstrand Parts, Sundstrand hydraulic Parts, Sundstrand Hydrostatic Parts, Sundstrand Sauer Parts, Sundstrand Danfoss hydraulic Parts, Sundstrand hydrostatic parts

Sundstrand-Sauer Danfoss: Hydraulic Components

 

[PutnamVictor]

It's a axial piston, variable displacement pump with a charge pump.

 

[slowzuki]

Sound like a closed centre pump. Should be able to block off the outlet. I don't think plugging the suction is a good idea if you are going to keep spinning it.

 

[J_J]

That pump is similar to the variable speed pump in our Power-Tracs. In our case, it is used in a closed loop situation. The fluid is just recirculated through the pump and wheel motor system, and the charge pump keeps the system full. The case drains in my wheel motors leak fluid , and this fluid goes back to the pump, and the pump case fluid which is about 10 to 20 % of the pump flow will flow out to a hyd radiator and back to tank. . My pump also has a 10 micron filter in the suction circuit for the charge pump.

What exactly are you trying to do.

Are you trying to use it as a general type of hyd pump?

It is designed to provide a variable flow to say wheel motors, and is like an automatic transmission. When you move the squash plate lever, the pump will pump more fluid at high pressure, and when in neutral, very little fluid is flowing. The charge pump will still try and keep the pump full, and flush out the case drain for the pump.

The valve that controls all this is called a squash plate.

Since the picture showed it being used in a mower, there would probably be two of these in a ZTR, and only 1 in a hyd tractor lawn mower.

So in general, it is used to send a variable flow of hyd fluid to a hyd motor, and that motor can be controlled from 0 speed to max speed. The squash plate, if turned one direction, the motor may turn fwd, and if turned the other way will turn in rev.

When using this pump, the terms used are open loop, or closed loop. Has nothing to do with open and closed center.

If you try and over work this kind of pump, the relief valves in the pump will activate.

 

[PutnamVictor]

The pump will continue to spin because it needs to provide power for motion. What I don't need is to provide power to implements because I have another hydro pump to do that. I do need the extra space that the existing spool and hoses are using.

"When using this pump, the terms used are open loop, or closed loop. Has nothing to do with open and closed center."
Can you elaborate?

 

[J_J]

Closed loop, means that the fluid is recirculated from the pump to the wheel motors, and back to the input of the upmp, with the charge pump making up any fluid lost via the case drains on some of the wheel motors.

Open loop is like most tractors. That means that the pump pulls the fluid from the tank, and pushes it around the circuit and then to tank. The expelled fluid from the wheel motors is sent to tank.

That pump will be turning whenever the engine is running, The flow of fluid is controlled by a small lever on the side of the pump, that rotates the squash plate to provide a little fluid or a lot of fluid, in fwd or rev.

There are relief valves in the pump in case the fluid is called upon to power a large load, and then the relief valve will relieve the fluid back to the input of the pump, until the load to power is equalized.

That is the way it works on my VSP.

 

[PutnamVictor]

I see. Well, from the diagrams it look like the pump is a closed loop, well at least the pump to drive motor is. The implement ports may be a different, they look to me as they can only be an open loop because it only receives fluid from the charge pump and returns the fluid at case pressure to the VDP. If this is true could I connect a hose from the output side to the input side? Will this through off the fluid pressures?

 

[J_J]

Tell me again what you are going to do with this pump. It seems you want to use the pump to supply fluid for something, cyl, motors, etc. This an expensive pump just to provide a few GPM's .

If you are thinking about just looping the input around to the output, that is going to generate a lot of heat. the VSP part seems to be a wasted asset.

Does the pump have another pump on it other than the charge pump.

My VSP pump has a 13 GPM hyd pump piggy-backed on the end of the transmission, that is turning at the engine shaft rpm.

If the VSP pump is turning, it can provide pressure, but it doesn't look like you want to use that part of the pump.

You might give Sundstrand a call and ask some of those questions.