Valve screeching

[Jay4200]

I quasi-successfully connected my hydraulic remote system for my snowblower, but ran into a problem with the valve. Everything works, but when the chute rotation cylinder is actuated, the valve screeches - like fingernails on a blackboard. The valve moves the flapper cylinder (virtually no load) silently, but the squeal is emitted once the stops are reached. This leads me to believe that it has something to do with the relief valve. I am guessing that the relief is set very low - there is a big nut sticking out next to the valve spools that I can guess is the relief control, but I don't know how to adjust it. Can someone full me in on relief adjustment procedures? I don't know what could cause sonic-frequency oscillation/vibration - can air cause that? Any thoughts?

 

[beenthere]

Sounds to me, from the description, it is the relief valve.
But seems that would be normal to sound off when the stops were reached.
Do you expect something different when the stops are reached?

 

[Jay4200]

Sounds to me, from the description, it is the relief valve.
But seems that would be normal to sound off when the stops were reached.
Do you expect something different when the stops are reached?

No - I've heard a "hiss" before, but never a screech. I would consider the screeching sound definitely NOT normal. AND, one of the pistons causes the valve the screech during all movement, not just at the stops. The chute rotation piston is under a fair amount of load compared to the flapper piston.

JayC

 

[KWentling]

I agree the screeching sound is the pressure relief opening and that is normal. I don't think the problem is the relief setting. Can you describe the circuit with the cylinder that causes the screeching when it is moving. Something is not right with it or it is moving extremely hard for some reason. Is this circuit using a regenerative valve, such as the bucket dump on a loader valve? If so, try moving the lever to the extreme right, past the detent. Does that cure the problem?

Kim

 

[Jay4200]

Is this circuit using a regenerative valve, such as the bucket dump on a loader valve? If so, try moving the lever to the extreme right, past the detent. Does that cure the problem?

I don't really know what that means. This is a dedicated valve set (2-spool DA 3-position each - no float, no detents) that runs the hydraulic chute controls on my snowblower. The chute rotation piston is pushing against a severe mechanical disadvantage with the hoop arrangement (see pic). Many times, I can't even pull the chute around with my arms on the ends of the hoop, while the piston is connected an inch from the center of the hoop. It must take many hundreds of pounds of pressure to turn that thing. It is fast though, even at idle. OTOH, the flapper piston is basically running wide open with virtually no resistance (it's really fast).

Most valves are set up with a ~2000 pound relief from what I've read, however, I was running my tractor at idle when I actuated the cylinders - can the pump can even generate that amount of pressure at idle?

JayC

 

[KWentling]

Never seen a setup like that. Looks like it could benefit from moving the cylinder out from the pivot point and using a longer stroke cylinder. That would slow it down and increase the mechanical advantage. Would also require moving the rear cylinder attachment to allow for the longer cylinder. Bigger bore cylinder would also slow it down and increase the power. All this requires $$$s. Maybe increasing the relief would be the answer. You will need a pressure gage to set it. Make sure the valve, hoses, cylinder, ect. are rated for the increase in pressure. You probably don't have regen on that valve.

Kim

 

[Gary Sweat]

I don't really know what that means. This is a dedicated valve set (2-spool DA 3-position each - no float, no detents) that runs the hydraulic chute controls on my snowblower. The chute rotation piston is pushing against a severe mechanical disadvantage with the hoop arrangement (see pic). Many times, I can't even pull the chute around with my arms on the ends of the hoop, while the piston is connected an inch from the center of the hoop. It must take many hundreds of pounds of pressure to turn that thing. It is fast though, even at idle. OTOH, the flapper piston is basically running wide open with virtually no resistance (it's really fast).

Most valves are set up with a ~2000 pound relief from what I've read, however, I was running my tractor at idle when I actuated the cylinders - can the pump can even generate that amount of pressure at idle?

JayC

I would check the pivot bushing or bearing on the chute. If it's that hard to move by hand at the ends of the hoop, it will be many more times harder for the cylinder to move. You may have a frozen bushing or a bearing that has come apart and binding up the rotating shaft. With the cylinder close to the pivot point, it will increase the amount of binding even more. Any pivot point should not create more than a small amount of resistance due to the weight it's moving.

 

[KWentling]

Gary beat me to it. On second thought, before you raise the pressure, make sure every thing is clean and lubed. I would even go to the point of taking it apart to be sure. Once that is done and if it still goes over PRV, then consider raising the pressure. I'll bet a good cleaning and lube job will fix it.

Kim

 

[Mace Canute]

Many times, I can't even pull the chute around with my arms on the ends of the hoop, while the piston is connected an inch from the center of the hoop.

That chute should rotate with much less force than that. As Gary and Kim said, take it apart and clean it, then lube it, maybe with a low temp grease or a dry type moly that won't act as a glue when cold.

Have you tried the setup without the cable to the chute hooked up? Or tried to cycle the cylinder without it attached to anything? Both would give you information that might be helpful.

Most valves are set up with a ~2000 pound relief from what I've read, however, I was running my tractor at idle when I actuated the cylinders - can the pump can even generate that amount of pressure at idle?

Yes, it will.

 

[J_J]

I would say that the chute is binding, causing undue force on the cylinder, and causing the valve to go into relief. However, it should go into relief at the stops as has been mentioned. Undo the cables and try to rotate the chute. If you can not, spray it down with penetrating oil, then lube it good. You should be able to rotate the tube by hand.