Relief valve problem

[Jay4200]

I built a remote/remote setup for my Kubota's snowblower a while back that included a dual DA valve for hydraulic chute control. This valve is mounted directly to the blower, and operates by taking/feeding the tractor's PB loop. The system works fine functionally, but the remote valves operate in relief almost all of the time (I must assume - the valve makes a high-pitched shrieking sound), unless the cylinders are virtually unloaded. For example, moving the chute flapper (which is virtually no load) is quiet until you hit the stops, although even the flapper valve will go to relief when the fluid is cold (<30F). I can make the valves operate silently if I feather them just a hair, but it is difficult to do - and pretty much impossible with cold fluid.

The relief valve may be defective, or may just be improperly adjusted - although both seem unlikely, assuming these things are tested at the factory. I know how to adjust the relief pressure on the valve, but do not have a pressure/flow gauge. I was thinking of buying a cheap pressure gauge and mounting it onto one of the extra inputs on the valve - I think that would work. In any case, I'm using it as is for now - but it is REALLY irritating.

Any suggestions on what to do or how to diagnose this issue?

JayC

 

[Willl]

Mourning Jay,

Does the valve on the blower have its own relief ?. If so, is it the one your hearing ?
Also if so, wondering if you could eliminate that relief and just use the tractors relief ?

 

[AKKAMAAN]

I think there might be a restrictor orifice in one of the fittings to slow down the action of the chute....need to feather the valve??

 

[DonnieP]

I added remotes awhile ago and they acted that same way, worked if feathered (not full flow though) and relieved if full stroke. When I traced the lines better, I found I had the supply and power beyond lines crossed. Switched them over to proper ports and worked great.
Donnie

 

[wdchyd]

Jay,

What you probably need is to disconnect that thing and I'll gladly haul it off for scrap metal........:laughing:

Kidding aside, you may not need all the pressure the PRV is dishing out......hooking up pressure guage (tee'd onto main input) where you can see it while running may allow you to tune it down during usage to see how much pressure is required to do your functions......

There maybe nothing wrong with PRV, just a design that "Sings"......

 

[Jay4200]

I added remotes awhile ago and they acted that same way, worked if feathered (not full flow though) and relieved if full stroke. When I traced the lines better, I found I had the supply and power beyond lines crossed. Switched them over to proper ports and worked great.

A mis-connect is highly unlikely, but I'll double check it. I suppose you never know...

JayC

 

[Jay4200]

Does the valve on the blower have its own relief ?. If so, is it the one your hearing ? Also if so, wondering if you could eliminate that relief and just use the tractors relief ?

Yes, and yes. And I've been wondering the same thing myself. If nothing else, at least wondering if I can count on the tractor's relief to prevent anything catastrophic if I played around with the relief setting.

JayC

 

[Jay4200]

What you probably need is to disconnect that thing and I'll gladly haul it off for scrap metal........:laughing:

You're too eager.

Kidding aside, you may not need all the pressure the PRV is dishing out......hooking up pressure guage (tee'd onto main input) where you can see it while running may allow you to tune it down during usage to see how much pressure is required to do your functions......

I was thinking of doing exactly that. 'Course, I don't have a gauge or adapters...

The chute flapper function doesn't need any pressure - it is virtually no-load with the piston load all of a pound or so. The movement is dictated by total flow rate, and that's just about the only limiting factor. I generally don't get relief on this function, but have when the oil is cold - that tells me something is probably wrong. The chute rotation function has quite the mechanical disadvantage back to the cylinder though, and there can be reasonable resistance in the chute (not a great design) - though I doubt that it could require the few thousand pounds that the piston should be able to push at relief - they're small, but look to contain at least a 2" piston. I think that there might be a flow restriction built into the cylinder connection (this part was already connected when I bought it) - there is a fitting on the cylinder that doesn't seem to be necessary - might be a DIY restrictor:

Eliminating the squeal is possible by feathering, but I have to crack the valve just the teeniest smidge to get it to move w/o noise and it isn't always possible. However, the rotation speed always seems about the same, so that teeny crack might be all the system can handle. Still, doesn't seem right at all.

OTOH, I used the blower yesterday (squeals and all) w/ 16" of settled snow from the last storm - ate through it like it almost wasn't there.

JayC

 

[wdchyd]

Yea, It may be a restrictor fitting....or just a pipe swivel adapter....the hole size will determine that......