Crossover Relief Valve or Not?

[lostcause]

I'm going to set up a loader mounted snow plow for winter - got the donor parts from an older Fisher 6.5 foot that's been sitting around for a while now. I'm wondering about the hydraulics though...

I was going to set this up on my last tractor and make something similar to the Deere 366 front blade, and when I studied the parts diagrams it uses a crossover relief valve between two single-acting cylinders and quick couplers to the the tractor hydraulics.

Looking at the AF11 loader mounted snow plow, it is just showing two single acting cylinders with hoses straight to quick couplers to connect to the tractor.

The question is what do I need for mine? I'm running a 3039R with a 3rd function controlled from the joystick thumb button to run the blade angle. I'm assuming that the loader mounted style is assumed to be run off the 3rd function and does that already have a relief valve in the system so it doesn't need an additional one.? The 366 front blade came about when loader mounted attachments weren't as common and electric 3rd functions were not around. Is that why it is needed in that system?

 

[Fallon]

If it's a true 3rd function there shouldn't be any problems. If it's a diverter, there will be problems. Regen on the curl circuit makes a pair of single acting cylinders work in 1 direction normally but not in the other direction. Read up on regen if it's a diverter.

For similar reasons a crossover relief valve works well on 2 equal sized single acting cylinders. But it wont work on a double acting cylinder as the 2 ends of the cylinder are different volumes. A crossover relief needs equal volumes in the cylinders or sides of the cylinder.

 

[RickB]

If it is a regenerative circuit you will have problems regardless whether the plow uses 2 single acting cylinders or one double acting cylinder. Not all loader valve bucket circuits are regenerative. Also, a snowplow with two single acting angle cylinders should have a crossover relief valve regardless of the control valve style. A crossover relief on a double acting cylinder will allow the cylinder to extend, providing 1/2 the benefit of the same valve used to protect two single acting cylinders.

 

[nybirdman]

I have a similar converted truck plow and third function(true) and added a cross-over relief after using with-out one for a couple years.
They do work;simple install,low cost.

 

[kennyd]

I'm going to set up a loader mounted snow plow for winter - got the donor parts from an older Fisher 6.5 foot that's been sitting around for a while now. I'm wondering about the hydraulics though...

I was going to set this up on my last tractor and make something similar to the Deere 366 front blade, and when I studied the parts diagrams it uses a crossover relief valve between two single-acting cylinders and quick couplers to the the tractor hydraulics.

Looking at the AF11 loader mounted snow plow, it is just showing two single acting cylinders with hoses straight to quick couplers to connect to the tractor.

The question is what do I need for mine? I'm running a 3039R with a 3rd function controlled from the joystick thumb button to run the blade angle. I'm assuming that the loader mounted style is assumed to be run off the 3rd function and does that already have a relief valve in the system so it doesn't need an additional one.? The 366 front blade came about when loader mounted attachments weren't as common and electric 3rd functions were not around. Is that why it is needed in that system?

That is a true 3rd function-actually it's a rear remote extended to the front, regen is a non-issue here.

I would definitely recommend a CRV for any loader mounted plow setup. We sell one, as does a few other suppliers.

 

[LD1]

The simple answer is yes you "SHOULD" have a CRV.

IF not you risk blowing a hose at best....or bending a cylinder/breaking the plow at worst if you catch a curb or hit something un-movable.

AS to 3rd vs diverter.....as a new layer in this thread.....either can work. IF it is a diverter and IF you have a regen only valve (two big IF's)....you can simply re-plumb the diverer to the lift/lower functions of the loader valve

 

[Dave M7040]

Remember with a FEL, the relief valve built into the loader valve is only able to provide any protection when a control valve is directing flow.

When the loader valve is in its neutral position the relief valve is no longer part of the circuit.

This lack of protection is why owners using forks on their loaders often damage cylinders when they use the forks tilted forward for pushing or back dragging objects.

Dave M7040

 

[PILOON]

Crossover valves in reality only protect the extended blade corner.
They work by dumping the extended cylinder contents over to the collapsed cylinder.

So if plowing snow away from a curb and U hit that curb the blade will then flip and dump your blade full onto the curb.

Personably I prefer the type of blade that flips if hitting a protrusion, like a rock or stump with the full flip blade winning over the cutting edge flip.
(I have just seen all too many cutting edge types very badly worn beyond repair.)
All 'flip' types depend on spring tension with some more easily adjustable than others.

The full flip style generally use eye bolts anchored at top of blade that are easy to adjust.

 

[RickB]

Crossover valves in reality only protect the extended blade corner.
They work by dumping the extended cylinder contents over to the collapsed cylinder.

So if plowing snow away from a curb and U hit that curb the blade will then flip and dump your blade full onto the curb.

Personably I prefer the type of blade that flips if hitting a protrusion, like a rock or stump with the full flip blade winning over the cutting edge flip.
(I have just seen all too many cutting edge types very badly worn beyond repair.)
All 'flip' types depend on spring tension with some more easily adjustable than others.

The full flip style generally use eye bolts anchored at top of blade that are easy to adjust.

Crossover relief valves protect the cutting edge, moldboard and any cylinder that is not fully extended or retracted.

 

[Industrial Toys]

I have used several much larger machines with snow blades, without any such relief and never had a problem. Did I just get lucky? Most blades have some trip means for obstructions anyway. I'm thinking that is way more important.

For what it's worth. My last blade has the bottom edge trip arrangement and I have had nothing but grief from it. Changed all the torsion springs, and that edge still trips without reason, often sending the loader sideways like an ice skate!

 

[ovrszd]

Before answering I had to reread the thread Title: "Crossover Relief Valve Or Not?" Based on that title my answer is "it's your choice".

If your thread title had asked a question similar to this the answers would be more definitive.

Does a CRV help protect my system?: YES.

Can I use my system without one?: YES.

Do you use a CRV on your snow plow?: NO.

If building a plow setup (which I did) would you use one?: NO. Because of my specific usage I didn't feel I needed one.

 

[lostcause]

This post was more about "is there already protection built in?" than it was "should I have one?"

Someone mentioned the loader valve, but that's not even part of this equation. I'm hooking the plow angle circuit to an electric / hydraulic 3rd function valve that sits directly behind the operators station, betweenand behind the rear tires and above the rockshaft housing. it has factory plumbing all the way to the front of the loader frame and is controlled by an electric thumb switch on the loader control. to date I have only used it on a grapple with a single cylinder - dual acting. I asked this because the factory Deere (Frontier) loader mounted snow plow (AF11) does not have a dual crossover relief valve according to the parts schematic . I was curious whether there was something about the 3rd function valve on these that would provide that sort of relief protection. The much older subframe mounted Deere plow (366A) has a dual crossover relief valve built in. Since that plow was only attached with the loader removed it would utilize the loader valve and its associated hydraulics for up/down and angle.

 

[Gordon Gould]

I have a CRV on my tractor plow (my truck plow also - Fisher builds them into their truck plows). The CRV almost never fires while plowing normally. The mechanical trip edge seems to provide adequate protection in both vehicles most of the time. However, when I stack or pile snow, which I have to do often, the CRV's fire quite frequently. When you push packed snow up into a pile the forces on the blade are very high and not evenly distributed across the blade. The CRV will protect your hydraulic components from the excessive pressures that would be generated if it wasn't there..

gg

 

[Industrial Toys]

I too ran my 6200 Deere blade off the electric valve on the valvestack, rear of tractor.

IF, I was doing contract work, in unfamiliar places, I think I would opt for a relief valve. Not only unfamiliar, but you tend to be in more of a hurry to get things cleared. Not a good combination.

 

[lostcause]

I have a CRV on my tractor plow (my truck plow also - Fisher builds them into their truck plows). The CRV almost never fires while plowing normally. The mechanical trip edge seems to provide adequate protection in both vehicles most of the time. However, when I stack or pile snow, which I have to do often, the CRV's fire quite frequently. When you push packed snow up into a pile the forces on the blade are very high and not evenly distributed across the blade. The CRV will protect your hydraulic components from the excessive pressures that would be generated if it wasn't there..

gg

Yeah, I'm familiar with how they work - both within a truck mounted plow and a stand-alone valve on a piece of equipment. I've had a few Fisher plows over the years - I live about 20 miles from where they make them and you see them at least 10:1 over all other brands combined here. I've had 8' & 9' straight blades, but the most recent was a 7'2" HS on a 2016 Colorado. All parts in that system were very light, to match the truck, but they also set the relief valves so that it took very little pressure to trip the relief and let the blade angle back and the fluid bypass (not to be confused with the blade trip system - that's all mechanical). I figured I would bend something because the metal was so thin, but the system was balanced perfectly so that didn't happen. I'm still stuck on why Deere didn't add one to the AF11...

 

[wdchyd]

Fisher and Meyers elec pump factory CRV’s are set at 3000psi (to protect the cyls), Fisher main PRV’s are set at 1750 psi (Meyers 1650) to protect the pump.
Not having a CRV results in a blown cyl barrel (or bent FEL frame) Seen it several times.