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.

 

[Jay4200]

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.

I can rotate the chute manually, but the mounting system is far from desirable. The chute itself is mounted on 4 pieces of slotted nylon - when everything is centered, it slides easily, but there is side-to side play, and it tends to hang up. I cleaned and greased all of the bearing surfaces, so it's as good as it is ever going to be. When the cable actuates the chute, the chute is pulled against the hoop-side guides, so I could guess that a lot of friction is created in the slotted guides on that side. The chute hoop does turn easily through the middle of travel, but seems to hang up right at the ends a little bit, although that area might already be outside the normal travel range. I have also removed cleaned and lubed the piston pivots, but have not disassembled the hoop pivot - it does have a grease fitting and I lubed it - I will take it apart and clean and lube it eventually. I agree, it is a weird setup - not only does it use excessive mechanical disadvantage, but it also creates a large moving object with sharp edges that is right in the middle of all of the hydraulics. Oh well, I'd expect no less from a French Canadian company .

I've been thinking of various ways to re-engineer the chute mounts - getting the chute riding on bearings would be infinitely better and would likely reduce the operating force by an order of magnitude.

That being said, lets assume for now that there is NOT undue mechanical force required to turn the chute, and it is moving as designed. There will still be a fair amount of pressure required due to the mechanical disadvantage designed into the system. Since the chute is moving at a reasonable clip while the valve is squealing, I'd have to assume that the relief blow-off is premature. Given all of that, what could cause a premature blow-off of the relief, and even more importantly, why would it squeal AND how can I make it stop squealing?

It is also possible that there is something either wrong with my valve, or the valve could be put together with incorrect spools maybe - don't know, although all of the functions seem correct. My downstream 3pt works, so the valve is OC and the PB works, and the work ports appear to be functioning as expected (except for the squealing).

JayC

 

[mmurphy]

Jay, to rid your self of the evils of wondering about valve, temporarily hook that valve function to a different cylinder such as your flapper, and then notice if still doing the screech.

 

[Jay4200]

Jay, to rid your self of the evils of wondering about valve, temporarily hook that valve function to a different cylinder such as your flapper, and then notice if still doing the screech.

That's easier said than done - no QCs on the piston-to-valve fittings...

JayC

 

[KWentling]

The squeeling when the PRV opens is normal. I would suggest you get a pressure gage and see at what pressure the PRV cracks at. You'll need a gage anyway if you reset it. Maybe it is set too low, but at one point it must have worked OK. Is this snowblower new to you? If you have owned it since new, has it always operated this way? Sounds like the chute rotation set up is about like my Kubota's. I can imagine how well it would work with a cable applying side pressure to it.

Kim

 

[Jay4200]

The squeeling when the PRV opens is normal. I would suggest you get a pressure gage and see at what pressure the PRV cracks at. You'll need a gage anyway if you reset it. Maybe it is set too low, but at one point it must have worked OK. Is this snowblower new to you? If you have owned it since new, has it always operated this way? Sounds like the chute rotation set up is about like my Kubota's. I can imagine how well it would work with a cable applying side pressure to it.

The snowblower is new to me this year. I just put together the hydraulic remote setup, so the valve and valve-to-tractor fittings/hoses are brand new - the chute pistons and existing piston hoses came with the blower.

Incidentally, how's this for a unique setup? (one more hose to mount...)

JayC

 

[Gary Sweat]

The snowblower is new to me this year. I just put together the hydraulic remote setup, so the valve and valve-to-tractor fittings/hoses are brand new - the chute pistons and existing piston hoses came with the blower.

Incidentally, how's this for a unique setup? (one more hose to mount...)

JayC

I don't remember if you said you tried this but have you disconnected the cylinder and ran it all the way out and back to see if there is any binding in the cylinder? It should move smooth and quite with no load on it. If it squeals without a load it can be the cylinder or something has gotten into the port blocking the fluid flow. Just something easy to try.

 

[rjmack]

air in the system will make it a lot louder.

i have the same issue with the snowplow on my truck, when it starts howling i just top up the reservoir and that quietens it down.

maybe your pump is cavitating, or perhaps there is some air trapped in your hoses, i doesn't take much time to look at the hydraulic system from the point of view of looking for vapour locks on a fuel system.

maybe you don't have enough flow on that circuit to purge the lines?

btw, air in the lines will magnify the noise problem through the relief valve.

do you have the fittings to plumb it so that the valve is the highest point in the system?

also, those hoses look to be way too long.

sorry for the nitpicking.

and... i would put 90's on everything

 

[Jay4200]

I don't remember if you said you tried this but have you disconnected the cylinder and ran it all the way out and back to see if there is any binding in the cylinder? It should move smooth and quite with no load on it. If it squeals without a load it can be the cylinder or something has gotten into the port blocking the fluid flow. Just something easy to try.

That is a good suggestion - I will do that. Unfortunately, I only have access to my tractor on weekends, so I have to wait a few days.

JayC

 

[Jay4200]

air in the system will make it a lot louder.

Air is a definate possibility - this occurred immediately upon starting the system up. I did not allow much time for the lines to purge, and the work lines likely had air them - this was the first couple of cycles on the pistons. I didn't want to keep going in case something bad was going on.

do you have the fittings to plumb it so that the valve is the highest point in the system?

I think the valve is pretty much the highest point in the system. Why? What would that do?

also, those hoses look to be way too long.

Hardly. The supply/return hoses are barely long enough - the 'IN' hose gets pretty tight when the 3pt is all the way up. The piston hoses are surely long, but they came with the rig (designed to plug across into tractor remotes), and I figured I'd change them and optimize the length if or when they burst or leak. If they never do, all the better - I'd just as soon not buy them. The hoses aren't secured yet either - it'll look a little cleaner once I get them all tied down...maybe. There is a lot of movement in the system - between the 3pt movement and the chute swing coupled with that huge hoop flying around - it was tough to route the hoses to get adequate length and clearance at the same time.

sorry for the nitpicking.

OCD strikes again .

JayC

 

[Gary Sweat]

That is a good suggestion - I will do that. Unfortunately, I only have access to my tractor on weekends, so I have to wait a few days.

JayC

Just be careful and don't let the cylinder hit you or anything in the way in case there is still air in it. If there's air in the cylinder it won't move for a second or two and then it can shoot out. Bump the valve a little at a time till it starts to move and go slow till it reaches full travel. Do the same coming back for the first cycle. After that, it should start to move smoothly.

It took me over a dozen cycles of the cylinders (disconnected from the loader) to get the air out of them and the lines on my loader. You don't have that much in the way of lines so it should clear out in a few cycles.

Just be careful, it's very dangerous to move a cylinder that is not attached to anything.