Squealing control valve

[SnowRidge]

I'm wondering if you have a valve designed for use with double acting cylinders.

 

[kennyd]

I'm wondering if you have a valve designed for use with double acting cylinders.

It should be since he is using two SA cylinders. There is no problem with that.

 

[kennyd]

Regarding system pressure, Isn't pump operating pressure dependent on load?

Yes, that is correct, but the PRV sets the max pressure.

What I don't remember doing is testing to see if port B was open to the return line when port A was activated.

It should be, can you provide a link or part number for the valve you are using?

Would a standard 4-way control valve be designed that way?

Yes.

 

[abcrepair]

That is an excellent thought!




What trouble could you run into? Please explain why you would want a relief set so low in a system that's max pressure is probably 2000-2500 PSI?

If you are using the factory valve the return oil will be going thru the out side passages of the valve. the return passages are not rated to see high pressure. that is why you should have a power beyond in the first valve in line. You should never see High pressure unless the cylinder is at the end of its stroke. One thought that just came to mind is maybe the angle cyl are plumed wrong, they could working against each other

 

[kennyd]

If you are using the factory valve the return oil will be going thru the out side passages of the valve. the return passages are not rated to see high pressure. that is why you should have a power beyond in the first valve in line. You should never see High pressure unless the cylinder is at the end of its stroke. One thought that just came to mind is maybe the angle cyl are plumed wrong, they could working against each other

Two SA cylinders are pretty hard to plumb wrong!

He is using a valve with a check valve on the input, so there should be no reverse flow putting pressure on the OUT port of his FEL valve.

Possibly this new valve is a regenerative type, and that is causing the slow movement...Won't know till he post's a link and/or part number.

 

[Farmerford]

bar:

You may have reinstalled the load check (also called lift check) improperly. If it is not opening properly, the flow into both the A and B ports will be restricted, but flow through the valve (when the spool is in neutral) will not be restricted.

With most lift checks, you can just remove the poppet valve and spring entirely and then reinstall the plug without them. You won't have a lift check, but if the valve then works properly it will confirm that you have a problem with the lift check. Since you are not lifting a load, I don't think removing the lift check will create any problem.

 

[SnowRidge]

Two SA cylinders are pretty hard to plumb wrong!

He is using a valve with a check valve on the input, so there should be no reverse flow putting pressure on the OUT port of his FEL valve.

Possibly this new valve is a regenerative type, and that is causing the slow movement...Won't know till he post's a link and/or part number.

If there is any kind of restriction anywhere downstream from the OUT port on the loader valve, check valve or not, pressure will build in the loader valve.

 

[J_J]

You would think ,after all the years since hydraulics was installed on tractors and other machinery, that the manufactures would put a hydraulic gage in the system for troubleshooting and maintenance. For less than $50.00 , everyone that owns/operates a tractor and other machinery could install a gage system to do their own diagnostic/problem solving. It simply involves a gage with QD's to plug into the system at key points on the tractor. An ideal setup would include a gage with a magnet attachment and a 1/4 hydraulic line,and when plugged into the matching QD, you can satisfy your self that the system is working or not working as advertised.

 

[abcrepair]

If there is any kind of restriction anywhere downstream from the OUT port on the loader valve, check valve or not, pressure will build in the loader valve.

Sorry I missed the part about the SA cyl.
To clarify my point if you are raising the FEL all the oil from the pump is going to the cyls and is protected with MRV the oil comming out of the return side of the cyl is flowing back to the valve and thru the return ports of the valve and out to the tank or in this case the prince valve. That oil in most valves is run around the out side where the casting is thin and has no protection or RV. now if you use the prince valve and it builds to MRV pressure you will see that pressure back to the FEL valve and the return passages. with or without the check valve at the inlet of the prince valve. I realy don't see the need for that check valve in this system. The proper way to add a valve after the FEL valve would be a power beyond sleeve in the FEL valve and a return line from the FEL valve to tank. most tractor MF sell PB kits. In this case if they don't then I would put a PB in the prince valve and put it before the FEL valve Ed

 

[bar]

I first of all want to thank everyone for taking the time to think about my problem and respond accordingly. I haven't done any further checking but I will after the holidays and report back here when the problem is resolved.

kennyd: The PA valve in question is a Prince RD2575.
Although there will be no reverse flow thru the FEL valve, there will be pressure. This pressure will be slightly higher than that required to angle the plow (loss thru the check valve) and per my current problem that will be the Prince relief valve setting of 1500psi.

abcrepair: I was unaware of the potential problems from back loading the FEL valve. That is good information. I considered putting T's on the FEL valve and running the valves in parallel but was told the series connection was good ..... and the plumbing seemed simpler. Guess I need to study up on PB.

I will get a pressure gage but at this time I feel there is a restriction problem and the Prince relief valve should not require adjustment. It would seem the problem has to be in the new 1/4" lines going to the SA PA cylinders, the QD couplers attached to the Prince valve or the valve itself. Unfortunately I used none swivel type NPT F couplers to add the new lines back to the control so disassembly will be cumbersome and I don't have spare mating parts for the QD's at the valve. But I will disasemble the suspected components and test them in my shop with air. I will also double check to make sure there is no mechanical hangup producing an excessive load but I think that is doubtful.
bar