Hydraulic help - pump cavitation with loader

[cobra2411]

I'm pretty sure the cub I just got has the wrong valve on the loader. It's a newer style mono-block two spool directional control valve. I have double acting cylinders on the curl, but single acting on the lift.

The problem I have is when I lift the bucket I hear cavitation. The warmer the fluid the less of a problem it is and the slower I go the less of a problem it is. I know there are other causes of cavitation including blockages, wrong fluid, etc but I can't help think it's the because of the wrong valve. I don't know enough about hydraulics though.

The curl cylinder does not have the same issue. Shorter stroke and double acting cylinders but I can curl all I want dead head it. There's a gauge and initially it reads about 1,300 but within 5-8 seconds it comes down to 1,200psi and stays there. I've held it for 20 seconds at a time trying to warm the fluid a bit.

Before I got the tractor the loader was removed to replace the clutch and when it went back together it got new hy-tran fluid. I have the remains of the 5-gal bucket. I assume there's just one hy-tran and it should work even in 25-30f weather.

On the lift cylinder one side of the valve is Tee'd to the cylinders and the other side it tee'd into a line between an aux tank on the spreader bar on the loader; a twin-draulic, and the fill port on the TC reservoir. My assumption here is that when I lift the loader the exhaust is open to reservoir, but there is still flow to the TC itself. So will that cause an unrestricted flow into the reservoir?

Thoughts, ideas, questions?

Thanks, David

[cobra2411]

Here's a schematic of what I think is happening.

[Jim Becker]

You don't show the pressure relief valve. Is one built into the loader valve? If so, how is it plumbed?

Your orange line inside the valve shouldn't be there if you are only showing connections while the valve is actuated. Your suction line goes from the reservoir to the pump. The outlet from TC is a return line to the reservoir.

What happens if you move the Touch-Control lever when the loader is lifting and making the noise?

[cobra2411]

The pressure relief is internal the loader valve. I have verified I get no more than 1,200psi when deadheaded. I'm not hearing a weak or leaking relief valve if that's what you're getting at.

I want to test using the TC while getting the noise; I have not yet.

If I understand correctly with an open center valve there's always fluid flowing from the P to the T ports. When you move the valve some fluid goes to the cylinders. I was trying to show that flow with the orange line. If we assume the lift is connected to the A port then that normal flow through the center would be open to the B port and ultimately the return reservoir. If I go slow then that internal "leak" will be small and the total fluid volume needed will be low. As I move the valve more the flow increases and I think I'm exceeding what can be fed to the pump from the tank.

Again, I'm no expert and I can be completely wrong but I do know a little about hydraulics and this seems right to me. Bottom line it has the wrong valve for those cylinders.

[SamsFarm]

Is there 7 ports on your hydraulic valve?

1 pressure
2 return
3 bypass
4 spool 1 a port
5 spool 1 b port
6 spool 2 a port
7 spool 2 b port

Your 2 spool valve looks newer than any loader ever made for a cub. I am wondering if it has the ability to be used with the one spool as a single acting valve. (Pressure up, float down!)

In the pdf manual section there is a manual for the 1000 loader.

Farmall cub > cub attachments > loader > International 1000 loader manual.

Pdf page 17 (actual book page 12) illustration 12a and 12b, you can see that the left side valve A or B port is plugged off.

In your pic of your loader valve it looks like you are using a A/B port to run with your tee to your aux tank and touch control fill port.

And in the illustrations 12a and 12b you can see the hoses on each side of the valve.

And in illustration 12a and 14a you can see the fitting and line coming off the bottom of the valve.

[cobra2411]

The pressure relief is internal and bypasses from the P to the T port. It's a 2 spool valve with a P port, a T port and 2 A and B ports.

My question exactly is "what happens when you use a 4 way valve on a single acting cylinder and tap one side back to the tank?" Can it cause a situation where the flow to the pump is exceeded?

And yes, the valve is a modern valve. It should have 1 4 way / 3 position and one 3/3 valve. A 4 way valve has P from the pump, T to the tank, A and B to the cylinder. Being open center in neutral P is connected to T internally and all the flow just goes back to the tank. In one position P is connected to A and B is connected to T. This sends pressure to one side of the cylinder and as the piston moves the fluid on the other side is returned to the tank. In the other position P is connected to B and A is connected to T - it's a cross-over.

On a 3 position valve neutral is the same P goes to T. In one position P is connected to B and the cylinder extends. In the other position port B is connected to T and the cylinder retracts. Port A is always blocked. They use the same casting, it's the valve inside that changes things.

Common valves from back in the day are the Gresen 300 and 400 series, a 3/3 and 4/3 valve respectively. From a parker catalog for the 300 and 400 series valves.

"The Parker Series 300 valve is designed to control singleacting cylinders or a uni-directional hydraulic motors. The spool in this valve is a 3-way, 3-position spool. The positions are power, neutral, and exhaust. “B” port is always the power port and “A” port is always plugged."

"The Parker Series 400 valve is designed to control a doubleacting cylinder or a reversible hydraulic motor. The standard spool for this valve is a 4-way, 3-position spool. The Series 400 valve cannot be converted to a 300 valve."

"The Series 400 valve does not have a load (reverse flow) check to prevent reverse flow when spool is in transition between neutral and power positions."

I have no idea about the Bulgarian valve that I have it it's equipped with a reverse flow check but from what I can find it's the same as having two 400 series valves.

So simple answer is it's not plumbed to a normal standard as it's using the wrong valve for the application.

I'm trying to find out if that's the source of my cavitation issue, which I think it is. The curl does not do it at all. Even dead cold right after starting.

[ricky racer]

You don't have the wrong valve. I believe you have too much restriction in the Tee'd line going to the B port of the lift cylinder valve and that is creating the cavitation you're experiencing. I'd suggest you completely change the configuration of the Tee, upsize any fittings comprising the Tee to reduce the amount of restriction.
One thing you could try before doing that is to try to bleed off any air that might be trapped in those lines. The Tee is the highest point of your hydraulic system and it could have an air bubble in or around the Tee that needs to be removed. To do this, slightly lift the bucket slightly (an inch or two) off of the ground using the tractor hydraulics. Crack the line, probably at the JIC swivel shown in the image below. The weight of the bucket will apply pressure to purge any air out of the line. Be aware, it will have some pressure behind it so have some rags ready and crack it slowly and give it time to push any air out of the Tee. Report back if that helps it any.

[inairam]

What loader is this? With just 2 pistons is it an IH 1000?

Do the hydraulics work on the TC? If not are you sure Is there a power beyond port installed in the control valve? The bypass block is really an auxiliary port series port. If you do not return pressure back to the TC you have no TC hydraulics and somewhat limited return to pump.

I found this out when I moved my loader from a cub ( which the PO used a pump from a number cub and hoses and no TC) to a 130 the replacement Prince valve ( installed by PO) needed power beyond the adapter installed to get the system to work properly.

I was seeing many of the same symptoms of some of the hydraulics working and some not or not well or working sometimes. I do not think the issue is related to oil temperature but more that the oil is not getting everywhere it needs to go in the volume it needs to.

[SamsFarm]

Sounds like you have a 6 port valve.

1 pressure
2 return
3 spool 1 a port
4 spool 1 b port
5 spool 2 a port
6 spool 2 b port

If so, your valve is not made for a power beyond setup (to run the touch control from the return port)!

I do not have a cub loader but what I see is in the manual is that the valve sends the low pressure into the aux hydraulic tank which then flows back into the touch control tank (no tee)!

Maybe your putting too much oil into your aux tank and not enough into your touch control fill port by the use or that tee.

Those quick couplers are not gonna help your flow either in a low pressure return.

Dont forget that a low pressure return line back to the tank is always bigger than the high pressure supply line from the pump.

And that low pressure return line usually have very few fittings and are low restriction!

[cobra2411]

It's not a power beyond setup, it's an open center valve. The pressure relief is internal and dumps into the T port, so when a cylinder is deadheaded the excess pressure bypasses and goes to the tank. Without the pressure relief when something deadheaded pressure would reach the maximum the pump could physically provide.

With the Tee on the one port I'm either aerating or cavitating. I've got to fix that first. Also, you're right on the fittings and the return line size. That's next on the list. Once it's plumbed the way it should be then I can continue diagnosing problems if there are any.

[Jim Becker]

I think the last two posters are on the right track. For one thing, return from the pressure relief built into the remove valves needs to go directly to the tank, not onto the bypass block. This is potentially a hazardous situation as one pressure relief is feeding another pressure relief. Those pressures can add to each other exposing parts of the system to double the pressure limit.

Your valve is a non-power beyond (or at lease configured as not power beyond) and is being used as power beyond. Maybe the valve can be reconfigured for power beyond, thus the earlier question about any unused ports on the valve.

Along the line of Ricky's comments, I wonder if the noise is a squeal from the valve or fittings and you are mistaking that for the sound of cavitation.

[SamsFarm]

Whether power beyond or not, the cub hydraulics system is open center!

[indy61]

I don't know if this helps but this link has some good photos of a Twin-Draulic loader similar to yours. You can zoom in and compare.

https://www.tractorhouse.com/listing/au ... p-tractors

https://media.sandhills.com/img.axd?id= ... SLTMYkU%3d

https://lh3.googleusercontent.com/kE6ZN ... wDZk=w2400

[inairam]

In the IH 1000 I needed to have the return on the loader valve to the local reservoir and Power beyond on the loader valve to the TC and an overflow from the local reservoir to the TC reservoir

when I hooked up the return to the TC I had the problems you discribe.

[SamsFarm]

Here is a nice schematic of the power-beyond set up from Prince Hydraulics



Only one image is showing up, so please check out the link!

http://www.princehyd.com/portals/0/techFAQ/OpenCenterPbDA.pdf