Open loop /closed loop question.

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callmefence

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I bought a Stanley hydraulic rock drill and jackhammer at a equipment auction. These are marketed as underwater tools and Stanley sells a hydraulic power station for them.
At 1000.00 for 8000.00 worth of tools I took a chance. Plus they are unused.
A couple of hundred more making some hoses and getting a bit for the drill.
Works outstanding except overheats the hydraulics very quick. A little more research the tools are open loop and the skid steers are closed loop.
Question is there a reasonable/ practicable work around or is it best to scrap the plan.
 

Atimm693

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I've never heard those terms before. But from what I understand closed loop is like a hydrostat, oil goes right from pump to motor and the change in flow comes from altering the displacement of the pump, or changing input speed. Open loop is more like conventional hydraulics, oil goes from pump, to valve, to cylinder/motor, and is returned to the reservoir. By that definition skid steers are open loop on the auxiliary/loader circuits, but the hydrostatic drive may be closed loop.

Are you using the skid steer to simply apply constant pressure via the auxiliaries? If so, the heating is coming from the machine running at full pressure against the relief valve continuously while the tool is not being used.

The remedy would be a power beyond kit, which is commonly done for implements that have their own valves, to reduce power loss and heating.
 
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callmefence

callmefence

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I've never heard those terms before. But from what I understand closed loop is like a hydrostat, oil goes right from pump to motor and the change in flow comes from altering the displacement of the pump, or changing input speed. Open loop is more like conventional hydraulics, oil goes from pump, to valve, to cylinder/motor, and is returned to the reservoir. By that definition skid steers are open loop on the auxiliary/loader circuits, but the hydrostatic drive may be closed loop.

Are you using the skid steer to simply apply constant pressure via the auxiliaries? If so, the heating is coming from the machine running at full pressure against the relief valve continuously while the tool is not being used.

The remedy would be a power beyond kit, which is commonly done for implements that have their own valves, to reduce power loss and heating.
According to my understanding which may be wrong. You have the definition correct but the terminology reversed. Open loop= constant flow
Closed loop= flow on command.

??????
 

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Open loop systems usually have a larger oil reservoir which helps with heat. I would think the open loop system with its constant flow would lend itself to working better with a cooler. I hope there is a workaround for you, sounds like a great tool.
 

Atimm693

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According to my understanding which may be wrong. You have the definition correct but the terminology reversed. Open loop= constant flow
Closed loop= flow on command.

??????

I may be wrong too since the aux hydraulics on a skid steer are already plumbed like a power beyond kit.

What size is the return hose?
 
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callmefence

callmefence

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I may be wrong too since the aux hydraulics on a skid steer are already plumbed like a power beyond kit.

What size is the return hose?
1/2".
The tools came with 3/8 whips and 3/8 skid style quick connect. When possible I always build 1/2 npt hoses for new implements to simplify repairs. That's what I did.
Reading on power beyond and I think you have me on the right track. My case I think has that feature. Haven't tried the drill on it.
 

simme

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I am wondering if the flow requirement for the tool is so much lower than the skid steer aux flow capacity that the skid steer is bypassing (relieving) a lot of fluid flow internally to compensate. I would think that that the tool flow requirement might be pretty low. Maybe a test would be to operate the ss aux hydraulics in variable mode at a low rate and see if it overheats.
 

Atimm693

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I am wondering if the flow requirement for the tool is so much lower than the skid steer aux flow capacity that the skid steer is bypassing (relieving) a lot of fluid flow internally to compensate. I would think that that the tool flow requirement might be pretty low. Maybe a test would be to operate the ss aux hydraulics in variable mode at a low rate and see if it overheats.

This is my thinking as well. Skid is running at max pressure against the relief continously, heating the oil, either because the tools are designed for an open center system (the valve is closed and will not pass any oil in neutral like a closed center would), or the pressure/return hoses are undersized.
 

Lucky

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Is the heat load why some skid steer implements have the case drain? Any fluid not needed is diverted back to the tank? I do a little studying on hydraulics but get lost pretty quick. Been studying a little on open center vs closed center because a sprayer I'm looking at has a hydraulic driven pump.

How about adding a flow control device to the drill?
 
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chevytaHOE5674

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Sounds like you need a SS with adjustable flow on the AUX circuit. You probably have a tool rated for a fairly low flow and your SS is providing was too much and over heating. A quick Google search shows the Stanley tools rated for 3-9gpm, most SS built in the last 10-15 years does double that without batting an eye on the low-flow side.

The case drain is exactly that. Some hydraulic motors needs a case drain that drains off oil that leaks thru internally. It needs an unrestricted flow back to tank.
 

simme

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A little more explanation on a case drain - some hydraulic motor designs (like piston driven motors) leak a little through the internal seals (like leakage by the piston rings in an internal combustion engine). That small amount of oil escapes the normal hydraulic circuit and won't be able to return through the return hose. The drain connection (third hose) allows the trapped fluid in the case (outer shell) of the hydraulic motor to drain back to the hydraulic reservoir. Without that case drain, the oil would eventually pressurize the case and blow out the seal on the driven shaft of the motor. Each drive motor on a skid steer will also have a case drain along with a case drain filter on the return to the tank. Those filters need to be changed or might eventually plug and blow out seals on the drive motor.
 

moses388

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Each drive motor on a skid steer will also have a case drain along with a case drain filter on the return to the tank. Those filters need to be changed or might eventually plug and blow out seals on the drive motor.
How often should that filter be changed? roughly...
 

dvcochran

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I am wondering if the flow requirement for the tool is so much lower than the skid steer aux flow capacity that the skid steer is bypassing (relieving) a lot of fluid flow internally to compensate. I would think that that the tool flow requirement might be pretty low. Maybe a test would be to operate the ss aux hydraulics in variable mode at a low rate and see if it overheats.
This.
The flow RANGE on the rock drill is only 7-9gpm. Assuming the skid steer is high flow, it is mostly deadheading. This is really hard on the pump. I would think you could hear some of this when operating the drill (but not actually drilling).
It would take some additional plumbing and parts, but I would think you could add a pressure regulator to the drill that could be valved in/out based on the machine it is being used on.
 
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callmefence

callmefence

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7-9 gpm should not be out of range for a standard flow ss operating at idle. The tool is open loop the machine is closed loop. I've seen some have hydraulic drive rakes with a open/ closed loop selection valve. Some older tractors used open loop hydraulics.
 

chevytaHOE5674

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Open center means oil is flowing all the time but zero/low pressure until there is demand.

Closed center means no flow but full pressure until demand. Pump dead heads and either destrokes or opens a bypass valve.

95% of the time open/close center has ZERO to do with the "implement/attachment". Open/closed is almost always a thing for the pump to spool valve. From the valve onward its simply an open loop when you pull the handle or hit the button.

On your SS when you activate the Aux circuit you are making it open center and oil flows 100% of pump output until you release the button.


My std flow SS will do nearly 18gpm at idle FYI.
 

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